text:
What hashing speed does my hardware have?
I'm checking this page to know what hashing speed my hardware has. But there's no explanation about the acronyms.
For my Core 2 Quad Q9650, what's the expected hashing speed?

The speed is in the Mhash/s column

Very related question: http://bitcoin.stackexchange.com/questions/118/how-much-bitcoin-will-i-mine-right-now-with-hardware-x

From Wiki:Mining hardware comparison: Core 2 Quad Q9650 - 18.67 Mhash/s . With current price and difficulty factor there is no point in using CPU for mining because the profit won't cover the cost of hardware or electricity. For example with current difficulty it will take you 8 years on average to uncover block and earn 50 BTC or 1/2 BTC a month if mining from a pool.
Today everyone uses video cards to mine e.g. ATI 5970 has about 800 Mhash/s, which is about 43 times faster then your CPU. Bitcoin network adjusts difficulty factor so bitcoin production rate would stay roughly the same, about 50 bitcoins per 10 minutes. CPU mining can do only a small part of total workload therefore you would receive on average a very small part of the reward.

The table in the linked page says it's  18.67 MHash/s. That's very low, mining with a CPU is pointless.

To explain why it's pointless... when you mine with a CPU you pay more in electricity than it would cost to buy the same amount of a bitcoin that you are producing.


text:
Does the Bitcoin client generate bitcoins automatically?
I mean, you just need to install the software, and with the time, you will get lots of bitcoins?

The bitcoin software only allows you to hold, send and receive bitcoins. Just like a real money wallet or bank account.

A couple of related questions: What exactly is Mining? | Is there any point to casual mining?

If it was easy to "get lots of bitcoins", they would be worthless.

You might want to checkout http://litecoin.org - it's an alternative to Bitcoin that is geared more towards "casual" users. With Litecoin, if you run the standard client, you will make some small amount of money, even without a mining pool. Litecoin are exchanged for Bitcoin at http://btc-e.com

Not really, there are a few issues you have to know about:

In order to generate Bitcoins, you have to be explicitly mining them. The standard client does not mine coins, it stores the keys you use to access them. You need to run a so called miner (like the GUIMiner) and you probably want to join a mining pool (like, Slush's Pool).
Even if you are mining Bitcoins, you probably won't make too many coins unless you have some good hardware. You should check out what hashing speed your hardware has and then punch the hash speed in a dedicated calculator.
If you want to mine coins by yourself (without pool), the chances of getting coins are pretty small, again, check the calculator and look for "Time to generate one block".

So in short, you need specialised software and hardware to mine coins, but it's not hard to get started.

It might be worth noting that once upon a time the default client did have this ability built-in, but CPU mining is adequately difficult as to be useless any more, so the option was removed.

Just to update: I'm not sure of the history, but as of Bitcoin Core 0.9.1, CPU mining is available but disabled by default. It's only suitable for testing.

The earlier versions of the client did include a "miner" which generated bitcoins.  At that time the network was young and the amount of hashing power was low.  Including the miner in the client made sense as it gave new users a tangible benefit and adding hashing power to the network was useful.  However the network is now more than a million times more powerful than the early network.  Most of the hashing power comes from high end graphics cards or custom built hardware (FGPA).
The option to use a CPU to add hashing power to the network (and earn coins) was removed from the client simply because the network the amount of hashing power it would add is minimal and thus the amount of coins the user would receive is negigible.  It was determined by development team that having a miner which used up electricity and no realistic chance of generating coins was a determent to adoption.
Today if you want Bitcoins there are three routes:
 - Invest in some powerful hardware to mine for them (add hashing power to the network).
 - Sell goods or services and accept payment in Bitcoins.
 - Use an exchange or person to person transaction to trade money for Bitcoins.
The reality is that as the network matures there is little need for every consumer to support the network.  The wallet & mining functions are no seperate specialized pieces of software.  As time goes on mining will likely become even more of specalized "field" where only the most efficient and largest miners can gain any significant revenue from mining.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

sort: votes


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What are the optimal cgminer settings for a AMD Radeon HD 6670?
I'm following this tutorial for mining Litecoins, and I'm having a little hard time finding the optimal cgminer settings for my AMD Radeon HD 6670. Any hint on that?
The tutorial gives this configurations for Radeon 7950 series GPUs (which is not mine):
timeout /t 30
setx GPU_MAX_ALLOC_PERCENT 100
setx GPU_USE_SYNC_OBJECTS 1
cgminer --scrypt -I 19 --thread-concurrency 21712 -o stratum+tcp://coinotron.com:3334 -u [USER] -p [PASS]

¿Have you had a look at this site?
https://en.bitcoin.it/wiki/Mining_hardware_comparison

Also, Con Kolivas descries in the SCRYPT-README an iterative process to find the optimal settings for any card, try following it and monitor carefully both the resulting hashrate (should be the highest possible) and the number of hardware errors (should be zero)

So far I have been using
-I 18 -g 1 -w 256 --thread-concurrency 2400
Getting ~71k/h with clock at 820 and mem at 852
I hope this helps

This is an old thread but I noticed it wasn't closed.
The previous answers are incorrect.
The correct answer is:

None.

You shouldn't be trying to mine with a 6670.  If anyone else finds this page, do NOT mine with this card. Most likely you are spending more money in electricity than you are making back.
Due to ASICs GPU mining is already being squeezed to the max and only really becomes realistic in fringe altcoin mining. But thanks to scrypt asics and god knows what else in the pipeline there is no point competing unless you have some of the top gear.
if you are dead set on wasting your time/money and burning out your old graphics card, here are the ideal settings taken from the scrypt mining hardware comparison:

-I 18 -g 1 -w 256 --thread-concurrency 2400

That will net you an average of 127kH/s.
For comparison a top of the line card will net you an average of 1,500kH/s.
Keep in mind also that not all vendors are equal, a powercolor card won't be nearly as powerful as an equivalent EVGA or XFX.

Ive been getting ~127kh/s with
-I 19 -g 3 -w 256 --thread-concurrency 2400
Half the time Cgminer wont boot, And the room its in is around -10C with a desk fan full blast on it, And the card still reaches 50C

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Can I see all transactions not included in a block yet?
I'm running bitcoind and would like to see which transactions I've received but haven't been included in a block yet. Is that possible, or do I need to run special mining software to see that?

The upcoming release of the Bitcoin.org client, version 0.7, includes:

getrawmempool

You could always check them on Blockchain.info


text:
How to calculate transaction size before sending (Legacy Non-Segwit - P2PKH/P2SH)
I know that I pay the transaction fee per kB, so how can I calculate how large the transaction will be before I send it via the RPC api. I run a site using bitcoins, and I cannot let the user's balance go negative, so I need to know if they have enough balance to cover the cost.

Assuming all the inputs you are spending are from regular "pay to address" transactions, each input will contribute 180 (plus or minus 1) bytes to the transaction.  Each output adds 34 bytes to the transaction.  And there's a fixed extra 10 bytes which are always present.
The "plus or minus 1" comes from the fact that each input needs a signature to be claimed.  The signature contains two 32 byte values, but if either of the values has a first byte of 0x80 or more, it has a 0x00 byte prepended to it.  So I'm assuming one of the two is high and the other is low.  That way I'm off by at most one byte per input.
So if your transaction has in inputs and out outputs, the transaction size, in bytes will be:
in*180 + out*34 + 10 plus or minus 'in'

For example, this transaction has 40 inputs and 16 outputs.  That gives us a transaction size of
40*180 + 16*34 + 10 +- 40

i.e. 7754 +- 40 bytes.  The actual size is 7761 bytes.
If the inputs are from "pay to pubkey" transactions then the inputs are smaller than for "pay to address" transactions.  And this will be different also for "pay to script hash" inputs too, depending on how/if that's implemented.
Edit: This transaction was made with bitcoins stolen in the Linode heist and shows a transaction size of 1337, possibly a deliberate use of leetspeak in the blockchain.
Edit2: Now that compressed public keys are commonplace, each input is 32 bytes shorter and so the transaction size is now:
in*148 + out*34 + 10 plus or minus 'in'

Is the formula described in Edit2 up to date with bitcoin v.0.9.0?

What about the size of P2SH ?

How do you find out how many inputs and outputs there are?

@MarcAlexander see In-Counter and Out-Counter: https://en.bitcoin.it/wiki/Transaction#Input

Here are some calculations based on the Protocol Documentation.
A Bitcoin Transaction is composed of the following:

Version (4 Bytes)
TxIn Count (1 ~ 9B)
For each TxIn:

Outpoint (36B)
Script Length (1 ~ 9B)
ScriptSig(?)
Sequence (4B)

TxOut Count (1 ~ 9B)
For each TxOut:

Value (8B)
Script Length(1 ~ 9B)*
Script (?)*

LockTime (4B)

Assuming a standard P2SH/P2PKH transaction is created, the script length marked in asterisk will be bound to 1byte as the Script Length is encoded as a variable integer; while the script size marked in asterisks will be bound to 24bytes as it will only contain a script hash.
So, in summary, we can assume that the maximum bound of each TxOut to be 34
bytes if we are paying to a P2SH/P2PKH address, since there are 4 opcodes in each output script. A great breakdown can be found here.
Assuming we are spending P2PKH outpoints for our TxIn. Our ScriptSig (composed of a 72byte DER Encoded Transaction Signature + 33byte Public Key) would be 146bytes in size and our script length will only consume 1byte as the size of the ScriptSig is less than 0xFD.
Therefore, a standard P2PKH/P2SH transaction spending a ONE UTXO redeemable with a basic ScriptSig paying to only ONE output is 189bytes. Otherwise, we can also further generalise this to:
in marks the number of TxIns
out marks the number of TxOuts
Assuming that in < 254 and out < 254.
Size of P2SH/P2PKH Transaction = in * 146 + out * 33 + 10
Computing the size of P2SH/P2PKH transaction that is being funded with complex inputs (i.e. UTXOs spendable with M-of-N signatures, hashed-timelocked contracts) is inherently difficult and is dependent on the complexity of the redeemScript used to produce the scriptHash of the prior P2SH transaction.

It is important to understand that the transaction fee you have to pay to make a payment is based on how you received the funds you are using to make the payment. The outgoing payment (assuming it's only to one place) is always going to be the same size. So the 'out' part will always have two standard "pay to address" scripts. The size of the 'in' part will depend on how many outputs you have to claim, which depends on how you got the funds.
So I wouldn't suggest charging the transaction fee to the person withdrawing, because then you're billing the user based on parameters the user has no control over. The transaction fees depend on things like how many transaction outputs you have to gather to get the coins needed. That's completely dependent on how your funds are structured.
Imagine if you walk into a candy store and are told that a candy bar is 35 cents, but then when they rang you up, they tacked on a 15 cent fee. When you asked them what it was for, they explained that the previous customer had paid them all in pennies, and in order to give you your change, they'd have to count all those pennies, and that takes more time.
I think you'd be pissed because that fee has to do with how their funds are structured and has nothing to do with your transaction. You would expect them to either eat those costs or build them into their prices. You wouldn't expect them to figure out exactly how much it costs to sell you a candy bar based on their internal business configuration and charge you personally based on that.
Either charge a flat fee per withdrawal (.01 BTC is currently common) or cover the transaction fees yourself. And use sensible strategies to reduce transaction fees. But, in my opinion, you really don't want to pass on that kind of cost to a customer.

"So the 'out' part will always have two standard "pay to address" scripts" isn't true.  Sometimes you have the exact amount in a single coin and can avoid receiving change.  See http://blockexplorer.com/tx/ef3d028f328147af14e96b3d0ed3500118faf05081cfd6f533de6af44eb5b9aa#i4577701 for example, which I created with the official client.

With the price of BTC at $7200, paying a fee of $72.00 for something small kinda sticks in the craw. .01 BTC/transaction is no longer a good idea.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Will mining significantly increase the power consumption of my PC?
I have a PC that is always on 24/7. I use it as an SSH and backup server, and it has a modest, not-too-great GPU that sits idle most of the time.
I hear a lot of talk about mining not being cost-effective for most people because electricity isn't free. However I'm already paying the electricity bill for my PC. I might as well let it sit and mine all day while it's on, right? Maybe help pay the electric bill?
Or will mining increase my PC's power consumption so much that it's still not worth it?

Yes it will. The component you're likely to use for mining is your video card (GPU) which consumes very little power when idle but can consume a great deal under load. Check this list of common cards and consult the Watts (W) column for how many watts your card is likely to draw. Any card worth mining on will probably draw at least 100 Watts under full load. Depending on the electricity costs in your area, it may cost you more in electricity than your coins produced are worth. There is at least one good calculator to estimate your proceeds but you'll need to find out how much your local utility company charges per kilowatt-hour for electricity to determine if it's profitable. For reference Kilowatt-hours per day = Watts * 24 / 1000.

Yes, it consumes more power. You can see, for example, by using a notebook from the battery. Turn on mining and you will see how your battery time goes down.
But unfortunately I don't have any data to provide you (saying for example that mining will consume 10%, 20%, 50% more power energy)... That depends how power-efficient is your computer processor, motherboard, etc. Maybe you should get a Kill A Watt Electricity Usage Monitor and test 24 hours with and without the mining.
In my opinion, if your computer is turned on all the time without high CPU usage, turn your mining on. If you are running a Unix-based OS, it should run on nice 19 mode, which means that any other task that the processor receives will have higher priority -- so you can SSH and/or backup just fine.

It is very dependent on the type of video card you have.  The mining hardware comparison has some solid info on watt/hashing power.  The short answer is yes, your power usage will go up a decent amount.

The power consumption of your PC will greatly increase by mining for Bitcoins, especially if you are effectively mining with one or more GPU and mining 24/7. If you are not a full time miner, I suggest you mine at night when electricity is cheaper. Also there are things you can do to cut down on the electrical cost to mine, for instance use an overclocking utility like MSI Afterburner or Saphire Trixx to download clock the memory as low as it will safely go (I recommend 180) You dont need memory clock to mine for Bitcoins and a low Memory clock will lower your electrical usage and your heat output. Also there are small steps you can take for instance do not leave the monitor on while mining, mine with a headless system from a USB flash drive, put as many GPU's in one rig as you can etc.

I am not sure if this is applicable to all countries or
How the companies set up power lines meters etc. but here in ph, if you are going to mine
It is advisable (if your not gonna do anythibg ekse) to turn off or unplug all other appliance chargers etc that your not using. The price per kilowatt depends and will go higher if you have a lot of appliance conduming the electricity all at the same time. Its good to mine at night time. My brother set up my extension chord connected to a sub meter. I use the extension for my pc only. So far, the kilowatt i consume a day ranges to 2-4 a day.
Depends on the intensity of mining and programs open or used. If mining alone with monitor off at intensity 2 and 4 my kilowatt a day is bet 1-2 :)

I don't think that is true everywhere. I know in the US, there are typically different tiers. In a lower tier, you will pay less per amount used, and in a higher tier, you will pay more per amount used. The amount of electricity you use will determine which tier you are in. But I don't think that part of it fluctuates throughout the day or month. I think at the time the bill is created, they determine which tier you fall in for that entire month based on the entire month's usage. So mining in any way will make you more likely to be in a higher tier, so you are less likely to be profitable.

That being said, it is also common that they charge less at certain times of the day in order to encourage people to use less electricity at other times. But those "discount times" don't depend on the amount of electricity you use during that time, it will be discounted during that time regardless. So if you are going to mine, you could play with the numbers to see if only mining during those "discount times" helps you be more profitable.

I wouldn't be surprised though if I am wrong and they do also measure peak usage and factor that into the bill...


text:
Where in the world is bitcoin mining the most profitiable?
This is a question for Bitcoin miners. High cost of electricity can really cut down on the profitability of Bitcoin mining. I want to know what geographic location has the cheapest electricity and thus most profitable Bitcoin mining in the world?

vote to close -- close to off topic and answerable with a single web search

Or the question could be refined to what factors should be considered when determining a geographic location when concerned with the profitability of mining.

According to the EIA:
http://www.eia.gov/emeu/international/elecprih.html
The cheapest electricity prices from their available data would be Kazakhstan at .052USD/kWh.
Although electricity cost itself would not be the only determining factor of profitability, it would be a major part.
Currently FPGA's seem to be the answer for best performance/kWh.  Some other factors to think about would be(not 100% inclusive of all the factors):

Difficulty in sourcing equipment to the country of choice.
Governmental taxes
Employee Cost
Weather Conditions(HVAC)
Government stability (Politics in General)
Ability of the power distribution network to handle your load.

I would say any place electric heating is in use. Computers are just as efficient at heating as electric heaters are, so the Bitcoins are effectively mined for free, as far as the cost of electricity and cooling goes, the two biggest costs. (You still have the cost, and depreciation, of hardware, of course.)

@Lohoris What do you think a computer produces if not heat?

The Watts of heat emitted by a computer just feel less hot than the same number of Watts emitted by a heater ;-)

@Lohoris please tell me you were kidding.  It is impossible for a computer to not produce the same amount of heat as any other resistive load.

This is only true if you use electric heaters. This assumes that mining is the most efficient way to heat a home. This answer may not be correct for 2 reasons: 1) How do you efficiently use the heat? 2) Electricity in not necessarily the most efficient source of heat energy. In some places, a gas heater is 10 times as cost effective as an electric heater.


text:
How to overcome the 21M limit of Bitcoins as adoption increases?
Are there any ways to increase the Bitcoin maximum coin limit, as a wider adoption would mean there would be a lot of real money chasing fewer number of coins? Also can one hold a fraction of a coin?

As long as it take x amount of time to make one why should there be a limit?

to encourage early adoption. Otherwise people might think "well, I'll think about it next year", instead of thinking - "only half a year of easy coins left? I better look into it quick!". Moreover, it gives Bitcoins value, because they won't be created forever - which is good for investors - "I can buy one millionth of possible entire future money supply for 100$? That's cheap!"

if bitcoins become a major currency, they will eventually be put into circulation, because everybody has to consume eventually. About stability: http://www.zerohedge.com/news/2013-04-01/so-much-stability-centrally-banked-fiat-era

A single Bitcoin is currently divisible up to 8 decimal places (giving you 21*10^14 units of money, or about 2.1 quadrillion units), nothing stops it from being divided further with small protocol change. In order to change the limit of Bitcoins created, one needs to change the protocol and force most of the Bitcoin network to adopt the change, which can be quite hard to do. This hard limit of the amount of Bitcoins is one of the features of the system, not a flaw - it is meant to fight against inflation. If for some reason you want a cryptocurrency without a limit (hint from Lohoris: you don't), try browsing for alternatives.
All in all, there will be enough Bitcoins to go around for everyone for a long while.

@Lohoris From otherpto currencies I know, it is the only one without a generation limit.

it may be, but still it shouldn't be promoted in any way IMAO.

Note that a change of the divisibility doesn't seem quite as simple as ThePiachu then thought.

The reason there is a cap to the amount of Bitcoins is to create a design that should increase in value longterm as opposed to decrease forever as FIAT does.
Noone would want to invest in a new currency that was designed to decrease in value.
Since there is no limit on how small size a Bitcoin can be divided to.
A single coin could be made enough to cover the whole earth if all the 21 million coins are lost.

Sounds convincing. Something worth investing in. Do you have exchange rate chart for bitcoin vs. USD?

@SumindaSirinathSalpitikorala Try http://bitcoincharts.com/markets/

Log scale, all data: http://bitcoincharts.com/charts/mtgoxUSD#tgSzm1g10zm2g25zvzl

Hey these charts are cool.

Well, there's coding.
Of course like many pointed out things, it might not be necessary. Every Bitcoin is divided in one hundred million units if I'm right. That should keep everything all right for now.
The thing is that a change like this (eliminating the limit) can cause problems with how the currency will be regarded (it can make it worthless). The alternative is to make more subdivisions...like splitting a Satoshi into 1000 units to keep miners mining but the thing is that miners have "tricked" the system already and they will continue to do so.

If thats the limit, look at this.
This is all money the world has:

This is the limit of bitcoins multiplying the current value +/- of the BTC:

Interesting that (imagining the BTC will stay at 4000|4500) the limit value of BTC will be around that, will never reach all money value the world has.

Bitcoins currently circulating in world Jan 2017: 16,366,275 BTC. This is translated to 65.465.100.000€

0,00654% of all money in the world.

This is interesting, but does not seem to answer the question.

I just find it interesting to add this info to this question. Satoshi didn't want for the first to change all world money into BTCs

Well then, what needs to be happening is similar digital currencies appearing periodically along the way because future generations should also have the ability to mine newly formed currencies so that they can enjoy the freedoms we can now. Silver runs alongside gold, never as valuable, but surely as effective a resource to be traded for goods and services. Likewise other digital currencies, should be freely capable of running alongside bitcoins for future generations to enjoy the value of.
Perhaps though, due to the lack of intrinsic value of any digital currency, which is essentially as great as the next massive EMP blast, the new digital currency should perhaps wait until bitcoins have grown substantially in value before lending itself as another easier currency to mine. And there should always be exchange rates between the individual digital currencies. However, we must be careful to avoid what was caused by having the gold and silver standards of our nation's past, provided popularity of digital currencies allows for such a problem as what happened back then.
However, I think that this is a great model. It's literally modeled after gold and oil, both of which are finite resources that have substantial value. One has been used as actual money and a measure of past national economies while the other has been used as a commodity more so than money simply because it is not readily available and traded for goods and services.
Everyone, please remember, bitcoins are digital, their intrinsic value is less than nothing because they essentially are absolutely nothing. This means that in order for them to be worth anything, very similar to our Federal Reserve Notes that we color green in this nation, someone has to be willing to trade viable currency for them or to take them in trade for goods and services. They're not like gold or silver, which are physical materials that anywhere in the world would generally take in trade for goods and services at a time when there was lacking an official currency.

This doesn't actually answer the question. Were you trying to comment on another post?

This is not an answer - it's a point of view. Please remember this is not a forum, but a Q&A site.

authors: Сергій Тараненко


text:
Can you inherit bitcoins without the private key?
Since the private key is needed to validate ownership, how does it work when you cannot access the private key?
Say X owned bitcoins and willed it to Y, but Y does not have X's private key. Say X's estate does not want to to give access to the private key or the location of the private key is untraceable.

Please clarify what "PK" do you use. Is it "Private Key" or "Public Key"?

PK = Private key

This may be interesting, even if it is pretty much purely theoretical: https://en.bitcoin.it/wiki/Contracts#Example_4:_Using_external_state

related: What happens to my bitcoins when I die?

Y can't spend the Bitcoins. You need the private key for an address to spend the Bitcoins from that address. There's no way around it.

It would be possible to use a multisignature scheme in order to will the bitcoins.
A 2 out of 3 multisignature address would be shared among three keys controlled by the bequeather X, the heir Y, and a trusted third party Z, for example the notary of X.
Any two parties of the three could move the money:

Bequeather X could change his will with the help of Notary Z.
After demise of X, Heir Y can access the funds with support from Notary Z.
Bequeather X and Heir Y could access it in advance for other reasons.

As Nick has pointed out, this would have to be done before the demise of the Bequeather, otherwise access would fall to whoever ended up in control of the private key, or the bitcoins would be lost if no-one regained it.

I've slightly improved your answer to make it a bit easier to understand. Please feel free to reverse any changes I've made or further improve it to your liking.


text:
Mining behind a proxy and restrictive firewall (only http ports allowed) - possible?
I have a very restrictive firewall with an additional proxy here. Is there a GPU mining tool out there that supports proxy server?
The best would be a SSL connection to the mining pool. A long living stream also doesn't work I think, because Internet radio is not possible.
I don't have a PC on the outside, so SSH tunnel is no option.
Edit:
Mining over a website could be a solution too. I tried http://www.bitcoinplus.com/ and it worked after setting the http proxy to a correct value for Java.

After searching and searching I found these possiblites.

Use bitminter Java client in Version 1.1.2 http://bitminter.com/client/1.1.2/bitminter.jnlp (current version doesn't work)
Make your own miner which supports proxy
Use a tool like Proxifier (I have not tested it personally, because it is commercial)
Use simpleproxy on a remote machine simpleproxy man page
Use stratumproxy.io (also supports SSL)

Most mining software supports connecting to a pool through any port. It is up to your pool to provide mining capabilities through the appropriate ports. I personally faced a similar problem when developing a pool implementation on Google App Engine - I only had HTTP and HTTPS ports available, and mining through them wasn't a problem.
As I doubt any mining pool would change their protocol to allow mining through HTTP ports, you can use any virtual machine to forward you mining traffic through them. For example, Amazon EC2 offers free virtual machine hosting for a year as far as I remember.

Amazon is only free for 750 hours. The main issue is to have a mining tool that supports a http proxy to connect through.

@otakun85 750 free hours per month equal to 31.25 free days per month, which should be enough for any month;). This way you could set up a SSH tunnel.

Sorry, you were right. I should have read it more carefully. But either way it only works for the first sign up. So you have to cheat to sign up more than once.
I may have found a way to use guiminer behind proxy/firewall. I try it tomorrow.

poclbm seems to support http proxy (looking at the source). But it didn't work

There are some pools which allow mining through port 80, e.g. port80.btcguild.com.
But I still search for a encrypted connection through HTTPS/ port 443. Anybody?

To have a pool with port 80/443 is one thing. The main problem is to find a miner, which allows to set a http proxy.

use one of http proxies listed at http://www.publicproxyservers.com/proxy/list_uptime1.html
for example:
./minerd --algo scrypt --url stratum+tcp://pool-server:port \
--userpass user:pass\
-P \
-x orlaproxy.info


text:
How is the exchange rate for Bitcoin established?
I noticed that there are exchange rates for Bitcoin to other given currencies. How are these rates established?

The answers to this question might help: http://bitcoin.stackexchange.com/questions/1405/what-happens-to-cash-used-to-buy-bitcoins

You have people that have BTC or currency already in their accounts.
Those people can claim: "I will buy/sell X amount of Bitcoins for Y amount of currency". If you divide one by the other, you have the exchange rate for that particular transaction.
If a buy and sell transaction overlap, they are executed and removed from the system.
After all such transactions are removed, you have a gap between the exchange rate at which people want to buy Bitcoins, and that at which people want to sell Bitcoins.
Average the closest buy-sell pair of transactions and you have the exchange rate, halfway between those two, or the price of the last trade may be used. In both cases, it's only an estimate of the price that the next trade will take place at.

I'm not sure point 5 is correct, don't exchanges instead consider the actual "last price" for that? Otherwise you could have a virtual value with no real meaning, such as people constantly raising the buy and sell price without actually ever meeting them.

@Lohoris This is why you have the bid and ask price that are different from that. But if you want to show the current price as one number, you have to take something between those. It is just more convenient than using two numbers, but yes, it doesn't tell you everything if you want to buy/sell.

maybe I wasn't clear: they do use only one number, only AFAIK it is not what you suggest, and it is the "last price" instead, which is a single number with an actual meaning (i.e. someone actually processed a transaction at that price). Look at the top-bar of mtgox.

this would suggest that the exchanges "conspire" to set the index price. Whether they directly each other what the individual sale prices are or they set their own price based on the exchange rate API of their peers.

Most exchanges use the double-auction market system for price discovery. Read more at
http://www.investopedia.com/terms/a/auctionmarket.asp
In economics-speak, the auction market converges where supply and demand intersect.

Right now, I could buy a Bitcoin for $6.62133 US and I could sell a Bitcoin for 6.62121 US. So the exchange rate is $6.62 :)

The simple answer is that it is the price at which a seller and a buyer of the currency agreed on a price for it; i.e. the price at which the market clears.  The sold currency is, after all, a commodity.
It may help you to strip away any superfluous notions to think of it as a pound of coffee or somesuch.  Seller Sally has coffee but wants dollars.  Buyer Bob has dollars and wants coffee.  Sally will not part with her coffee for less than $4.  And Bob will not buy coffee for more than $3 dollars.  The market fails to clear at these prices.  A new seller, Sam enters the market and is willing to sell his coffee for $3.50.  And a new buyer, Bill, enters and is willing to buy coffee for $3.50.  Sam and Bill exchange coffee for dollars.  This fact is published to the rest of the market participants; who are thereby able to conclude that at some point in the recent past that two participants were able to transact at the price of $3.50.  As an entrant to the market, are you guaranteed to find another buyer or seller at that price?  No.  But it's a useful piece of data.
If you really want to know how this -- and economy in general -- works, you'll have to do a little reading.  As a start, I recommend:
Murray Rothbard, Man, Economy, and State
http://mises.org/rothbard/mes.asp
Ludwig von Mises, The Theory of Money and Credit
http://mises.org/books/Theory_Money_Credit/Contents.aspx

The MtGox exchange rate for bitcoin to USD is established in a 24/7 free market where bids meet offers to generate a last trade price. The bid/offer spread represents the distance that market participants are willing to buy or sell their bitcoin. This is no different than any other free market or any other free-market exchange-determined commodity price. See; http://mtgoxlive.com/orders

Here's an example of this -- using the BTC/PLN market on Mt. Gox: http://bitcoincharts.com/markets/mtgoxPLN_depth.html

It is established by people posting buy and sell orders.

This needs much more detail to be useful. How is it established by buy and sell orders?

This is an old thread from 2012.. now 8/1/2017 bitcoin price is $4200.. how quickly things change
Coming back to the question - price of bitcoin is determined on exchanges. to understand how the price of bitcoin changes you have to understand how exchanges work. Only a small fraction of all coins in circulation are deposited on exchanges. The main reason of price fluctuation is the relation and volume of demand and supply. There are other factors too, technological advancement which can only be accessible with bitcoin give bitcoin a huge boost.
Bitcoin was the best performing (fastest growing) currency last year
http://www.xrates.org/bitcoin-charts/

How is the exchange rate for Bitcoin is established based on supply and demand.
Supply
Thee rules of Bitcoin, as they currently stand, say that this supply number will slowly go up and hit a limit of 21 million eventually.
Demand
There are really two main sources of demand for bitcoins:

Demand for investment
Demand for mediating fiat-currency transactions

The actual price calculation can be done as explained here: Model for calculating the exchange rate of Bitcoin

Bitcoin exchange rates are determined by the forces of supply and demand. The more people who want to buy Bitcoin, the higher the price will go. The more people who want to sell Bitcoin, the lower the price will go.
The price of Bitcoin is constantly changing, as the market reacts to new information and events. You can find the latest Bitcoin exchange rates on a number of websites.


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How does Ven work compared to Bitcoin?
The Ven FAQ states that Ven is a basket of currencies, but how is it determined? Is it done privately or in the style of a committee? What trade offs are there in relation to Bitcoin?
Links: official site, wikipedia entry

Hello and welcome to the Bitcoin SE. Please add links to relevant information about Ven and its FAQ you are reffering to for clarity.

While we do allow questions about non-Bitcoin cryptocurrencies (a la NameCoin, IXC, TBX, etc) non-crypto currencies are off-topic here. I don't know enough about Ven to say whether it belongs or not. Does anyone out there have better knowledge to share? Simply adding "compared to Bitcoin" doesn't make things any more on topic than adding "as a programmer" on programmers.stackexchange.com.

I'm uncertain as well - it does appear to be a meta-currency rather than a cryptocurrency. It seems to also be a competitor to Bitcoin at a functional level. Whether it's just another fiat representation like SDRs or has something structural that Bitcoin can adopt, I don't know.

It appears to be completely unrelated (hence the close vote I just casted).

Ven is a digital social currency used to share, buy, sell and trade in
  the world of Hub Culture and beyond. The value of Ven floats against
  other currencies and the price is based on a basket of currencies,
  commodities and carbon futures.

,

Can I trade my Ven back to national currencies like the Dollar, Euro or Pound?
No

Apparently it's just a bad-old centralised virtual currency.
Nothing new, nothing special, nothing relevant. And definitely nothing related to Bitcoin.
since I just skimmed over it, I might have got something wrong, but as far as I've read that's unlikely

If you agree, please just cast a close vote, thanks :)

Close vote and +1 to you.


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How can Bitcoin work with Ven?
Bitcoin and Ven seem to have very different properties, so are there any complementary ways for them to interact? Maybe with Ven acting as a universal fiat representative?

At present I'm not aware of any ways that Bitcoin and Ven interact, but from what little I know of Ven there's no reason they couldn't interact in the same ways as any traditional currency. I see no compelling reason why a Bitcoin<->Ven exchange couldn't be opened, though I don't know if Ven allows chargebacks. Ven might also be useful as an analysis tool, since it essentially represents a "basket of currencies" and therefore the price of Bitcoin in Ven might be a better indicator of Bitcoin's actual worldwide value since differences in value of local fiat currencies would have less of an effect on the BTC/VEN price than say BTC/USD or BTC/PLN.
Update: Apparently, Ven is a private, local currency which cannot be converted back into other currencies, so the above may be inaccurate. Ven does allow private exchanges, though, so it may still be possible to build an exchange.

According to their FAQ, Vens can't be converted back to local currencies, so there's no chance of having an exchange. Pointless.

Ven's a private, local electronic currency, like Facebook credits.

Ven does allow person-to-person (P2P) transfers, so just like how over-the-counter (OTC) transfers occur enabling the conversion from PayPal to BTC, anyone wishing to give up their bitcoins in exchange for Ven, or vice-versa, can do so as long as they find a counterparty willing to trade.
I might have been the first to offer to exchange my Ven for BTCs.  At one time I had an open listing on the #bitcoin-otc marketplace.  I've never known of anyone holding Ven nor have I seen anyone wishing to exchange the Ven currency.
I currently have 15.0 Ven available.  The exchange rate is about 1 Ven = $0.10 USD.  At about $4.50 BTC/USD that means the BTC/Ven is about 45.0.  I'll even double that -- and give up my 15.0 Ven for just 0.15 BTC.  Any takers?
The Hub online store has goods and services you can purchase using Ven, but the prices are not competitve from what I've seen.  e.g., if you were to convert the price in Ven to dollars using the exchange rate, the listed price is much much higher for the same item than the price from other merchants.
I suppose if there was a distressed sale by someone who held a fairly large enough amount of Ven then the buyer could use the Ven to exchange it for something like bullion sold through the Hub Culture online store and then make a profit doing that kind of trade.
But if you'ld like my 15 Ven, make me an offer. :-)
I'm on the #bitcoin-otc marketplace (IRC channel).

Heh, why the downvote?

I didn't downvote, but probably for the advertising. Mentioning that you tried to sell Ven for BTC is not relevant to the question. Once was a joke, twice is IMO too much.


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How do I import to MultiBit from Blockchain.info?
I have a single password and a yubikey on my account at blockchain.info.
When I try to import the wallet.aes.json file nothing happens.
When I select the import file, MultiBit never displays the 'Number of Keys' or 'Replay date', so I put in my password and click "Unlock" then click "Import Private Keys".
The Bitcoin addresses in my account never show up on either in the send or request tabs.
I have also tried importing the unencrypted base58 json file from blockchain.info and it too has the same behavior (save entering my password).
Could you please point out how to export my wallet from blockchain.info to MultiBit?

Step one : Update your Multibit, normally since 0.3.4 it can import Blockchain.info
https://groups.google.com/forum/?fromgroups=#!topic/bitcoin-multibit/G87Y3e1-0Ak
Anyway, if it's not working you can try this :
Go to Import/Export in Blockchain.info
Now "Export Unencrypted", change Base58 by Bitcoin-Qt format and take the key after "priv".
Now go to Multibit and EXPORT (yes export) your wallet WITHOUT password.
Edit the file exported and you'll see several lines with ADDRESS (whitespace) DATE
Replace address with the blockchain's address. Change the date by the date you created the account (or a few time ago).
Now save and import this file in Multibit, et voilà !

I've tried running the import for blockchain.info format in multibit 0.5.9, which is why I'm so confused. I don't get any errors about incorrect formats, or inability to decrypt the file. I don't get any feedback at all.

Strange indeed, but you can try the second option :) I don't know if it's exactly Base58 but you'll find that easily in the file exported.

authors: Æløñé Jübø Mîñåty


text:
GUI Miner for OS X?
I'm pretty new to the world of Bitcoin; though, a few months back I tried mining. I had everything working, but then I stopped.. Anyway, now I'd like to start up again, though I've wiped my computer and reinstalled OS X since then.
I had been using a GUI (GPU) Miner, but now I have no idea how to find it.. I think it had something to do with poclbm, but I can't be sure... Anyway, if anyone has had any luck with one, please inform me.
Thanks.
Btw: I'm running 10.7.4

MacMiner is the first and best native Mac GUI for bfgminer, cgminer and cpuminer
MacMiner website

Agree with John.  I had issues authenticating when I used Asteroid.

I guess you are referring to GUIminer.
I would also recommend looking at the excellent BitMinter miner, which has a nice GUI and runs great on Mac OS X. I should probably mention that I made it. ;)

I use DiabloMiner. Here are some quick start instructions for it.


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What does PPS mean/stand for?
On many mining pools/bonds I see things listed as 105% PPS / 110% PPS weekly payout.  What does PPS actually mean?

Where I've seen it, it refers to the mining payment method "Pay per share".
This question has an answer that describes what a "share" is.
On some mining sites that have existed, the earnings for a share have been essentially paid immediately. However, this method exposes the pool operator to a possibility of loss in the case that, on average, they find less that the expected number of blocks. This can be made much worse by a large miner participating in the pool and performing a block-withholding-attack. To prevent these problems, most pool operators prefer slightly modified pay-per-share methods of payment, such as SMPPS (Shared Maximum Pay Per Share).
A payment method is not strictly Pay Per Share if the earnings aren't available for payout immediately, or if risk is passed on to the miner. Note also that it may not always be clear how much of a fee is being charged by a pool operator; it can be as low as 0% or as high as 7% (but if they tell you the payment per share, you should be able to work it out by dividing the block reward of 50BTC by the current difficulty and comparing it with what the pool pays).
A pool would not payout 105% or 110% except perhaps as a promotion when it is trying to increase its number of participants and offers an increased reward such as 55BTC per block (ie 110% of what is earned) at its own cost.
Update: The discussion you linked to in your comment is regarding the issue of mining "bonds" where the issuer promises to pay 110% of the shares mined. Each bond appears to be selling for around 0.6BTC, and represents 2Mh/s of mining speed. Given that the bonds are "perpetual", presumably the issuer has allowed for equipment replacement and maintenance costs, and power etc. Payouts are advertised as "currently 110% of PPS", so it is presumably a promotional offer. The issuer must be earning a margin somewhere along the way to cover the cost.

An example would be with a mining bond that can be reviewed at the following link.  It states, "weekly payouts are 110% PPS".

The explanation is that "First, I will be doing merged mining so those coins will be used to increase the pay per share.  Also, I would like to offer a good value for each bondholder", however my understand is that merged mining only increases return by 1% or less, so the promoter appears to be offering coins from his own pocket. Would be enough to make me suspicious.

@HighlyIrregular: Where mining bonds are concerned, 110% PPS is nothing more than a cheap marketing gimmick, designed to give the illusion of differentiation for what is essentially a commodity. Offering a 100% PPS bond for 0.3 BTC is equivalent to offering a 110% PPS bond for 0.33 BTC. Whatever the issuer needs to pay for the extra has already been priced into the issuing price, which is generally higher than the operating cost of the issuer.

@HighlyIrregular: PS At the cost of the appearance of shameless self-promotion, I think you're confused about what a mining bond is, and you might want to have a look at the thread where by all accounts the concept of a deterministic mining bond was invented, https://bitcointalk.org/index.php?topic=65569.

@MeniRosenfeld, I think I figured out how the bonds work somewhat after posting that comment. It's probably worth mentioning that in the case of bonds referred to by this question, one bond is worth 2Mh/s, but the current promotion offering 110% payment makes them temporarily worth 2.2Mh/s for the duration of the promotion. It's not a long term commitment, so wouldn't justify a 10% increase in the bond purchase price though.

@HighlyIrregular: The way I understand it it should be at least 105% forever. The 110% promotion which is possibly temporary makes things worse, the payments are not determinstic but are rather decided by the issuer's whims.

PPS is "pay per share", a mining pool reward system where the operator gives a set payment per share submitted proportional to its average worth, regardless of how many valid blocks the pool finds. This way the miner doesn't suffer any variance.
By extension, 100% PPS is the reward that would have been given for a certain hashrate at a PPS pool without a fee. 110% PPS is 110% this amount, etc.
Some pools, for example Chaang-Noi's project, are really pool-hopping proxies so they are able to offer >100% PPS to miners. Things like merged mining, preference for newly generated coins, attacks on Bitcoin or alternative currencies or using the hashrate for things unrelated to Bitcoin - or proxying to gpumax.com, which itself is based on any of the above - can also allow a pool to offer >100% profitably. It could also be a promotional offer.
Some mining bonds state that they pay >100% PPS as a marketing gimmick.


text:
Is there any good reason to buy Bitcoins?
I've read the introduction to bitcoins. But the main question remains: what reasons could push me to buy bitcoins today?

Hmm, question might appear to be a bit localised, what do you all think? We probably can get some decent question out of it, but I can't really put my finger on what should be changed...

For speculation, you would buy when the price is low in anticipation that the price will rise in the future.
There are some signs that the currency is seeing wider use and has greater potential in the future.  For instance:
 - http://blockchain.info/charts/n-transactions
Concluding that that growth means that a bitcoin will be worth $4 or $2 or $32 by any certain date is more or less speculation though.
As far as why you might want to buy bitcoins today?
How about to participate in an online lottery where the jackpot payout return is 99% of the total wagers.  Beats the heck out of doing a scratch-off at the gas station.  Tickets are about $1 each.
 - http://www.bitlotto.com
How about for the novelty.  Have you ever bought a quart of pure maple syrup direct from the farm?
 - https://bitcointalk.org/index.php?topic=55594.0
or Alpaca socks?
 - http://www.grasshillalpacas.com/alpacaproductsforbitcoinoffer.html
or a Blue Canary Night Light:
 - http://bluecanarynightlight.com
How about to prove your brilliance?  Bets of Bitcoin is a predictions market.
 - http://betsofbitco.in
Maybe you want to purchase something and would rather that purchase not show on your credit card bill.  Or not.
Or maybe you want to make a purchase from someone on Craigslist and don't know if you can trust that they'll ship your order.  There are escrow services (with dispute resolution) available using bitcoins (compare BTCrow's 1% to escrow.com's $25 minimum fee):
 - http://www.btcrow.com
Maybe you want to send a few bucks to someone in another country as an expression of appreciation.  Bitcoin transfers are nearly instant and know no borders.

Bets of Bitcoin is not a prediction market.

Indeed - Bets of Bitcoin is not a prediction market, but predictious.com and fairlay.com are.

To participate in a disruptive technology
Many of the other answers are covering the investment angle, but also consider that Bitcoin is a disruptive technology. Bitcoin allows an individual the kind of control over their money which has never been available before in all of history.
This is a very big deal. It is now possible to send any amount of money, to anyone, anywhere in the world, anonymously (if you're very careful) in moments. This was not possible before now for a multitude of reasons:

governments restricting destinations / amounts
banks not having a presence in some regions
excessive fees (particularly for small amounts)
unreliability of some postal services

All of the above may or may not concern you, but they do affect the lives of many. By offering an alternative Bitcoin can potentially bring about a societal change in the same way that mobile phones and email have. Already the idea of sending someone some small change, in bitcoins, as a reward for their creative efforts has become commonplace to me.
The knock-on effect of this is to encourage that author or artist to produce more, and the world becomes enriched. In volume, those bitcoins can free them from a tedious day job and allow them to pursue their dream.
Surely, that's worth a bitcoin.

If you are a student from China, studying in the UK (say) - you can buy bitcoins on btcchina.com directly from your Chinese bank account, send them to Intersango.com and sell them for GBP, and transfer them to your UK bank account.
You can avoid having to send thousands of pounds to a British bank account to cover your expected expenses and instead just convert your money as and when you need it.

Bitcoins are currently semi-low in value, if you think they will go up in value, they are a good investment.

One can expect their value to rise due to the bock reward being halved in about a year.

If you suspect your local currency or banks available to you to be unstable (say, you live in Greece and you want to stay away from the greek banks), Bitcoins might be a more preferable solution to standard banking. Nobody can steal your coins.
If you like new tech gadgets, getting to know Bitcoins as a possible new "thing" on the Internet might be up your alley.
If you are performing a lot of online money transfers, especially between countries, operating in Bitcoins can save you some money.
If you are dealing with people that already accept Bitcoins, it might be a necessity for you.

But in the end, there is no real reason to be "pushed" into using Bitcoins (at least currently). If you organically find Bitcoins to be a better solution for some problems you encounter, you can try them as an alternative. Other than that it's still a new technology for enthusiasts, computer-savvy people and speculators. If you don't find any reasons to buy them currently, chances are it might take some time before new reasons appear.

The kind of obvious reason is that you want to have some bitcoins for some reason, but don't want to run a mining rig. In that you need to exchange something else for bitcoin, that something else might as well be dollars or euros (or whatever your local money is)

While I like all the bullets in the other answers, for me they're currently more novelty than actual use.
IMHO, the major, number one reason to buy Bitcoin today is speculation. In some scenarios it could rise to $100, $1000, even $1,000,000 per BTC is not inconceivable. With this potential uptake, I think it's totally irrational not to invest some amount into BTC (it can be as little as 1 BTC if you're relatively bearish, but with today's prices, if you're bullish, you can still acquire a large chunk of BTC without tossing a fortune into it).

The crux of your argument is your estimate of the probability of reaching some value level.  That estimate is certainly debatable, making your claim about irrationality a bit of a red herring.  That is, your claim is that you believe with p% probability that the value will change by $X, so then you should invest $Y in BTC.  The rationality of that depends on your subjective estimates of p and X.  p could be < 50%, X could be negative.  The variance of these estimates could be large.  --- My point is that it takes a lot of work to convince oneself this is a good investment.

@cape1232 - I think it's a huge risk, but the probably of "winning" just can't be that minor. So, it's "easy to see" that the expected value from the investment is positive, even though the risk might be 99.99% - so it doesn't necessarily make sense to invest all your life savings in BTC, but it does make sense to buy just 1 BTC.


text:
Are there algorithms that could have been chosen for mining that balance CPU/GPU?
The mining algorithm for Bitcoins (and most alternative but similar currencies as well) is purely computation hard, but not decision hard or memory hard. This caused the unexpected effect that GPUs are insanely good at mining and CPUs are so bad at mining that there's almost no point in using them to mine.
This has had many effects, including the concentration of mining into specialized hardware. Suppose that I think that's bad and would prefer that commodity CPUs be optimal for mining and that mining on them be practical. Given the requirements of mining, particularly that it work like a lottery and that valid results be quickly verifiable, are there algorithms that could have been chosen that would have resulted in commodity CPUs being the optimal miners?
Are there algorithms that require lots of decisions and/or lots of memory that could serve as the mining algorithm on future crypto-currencies that would make CPU mining practical again and give everyone with a high-end CPU a reasonable chance at mining?

Interesting idea. However, even if there was an algorithm that favored commodity hardware it would still not put mining back into the hands of the people because of bot-networks. Maybe there needs to be an additional requirement of human input, like a CAPTCHA.

@Thilo Can you imagine the tedium of endlessly answering CAPTCHA questions to keep a currency operational?

I don't think a computer can easily verify a CAPTCHA it didn't generate, so that wouldn't work. Good point about botnets though, that's a serious problem.

What would be even better would be some sort of algorithm that didn't require upper end hardware of any sort, and used less electricity to run. I can't imagine how that could work though - even if you based chances of solving a block on something like the combo of the current time and your IP address, you'd still get an advantage by using lots of IP addresses (and it would also result in stacks of low value hardware participating, instead of a lesser amount of high value hardware). Finding some sort of activity to perform that benefits people at the same time would be the ultimate achievement.

Year and a half after you originally asked this question, LiteCoin uses scrypt as a CPU-friendly algorithm, while PPCoin uses "proof-of-stake" to balance the electricity expenditures required for "proof-of-work". In retrospect, do you think any of them would've been a better BitCoin design than the original one? :)

@JoePineda: No. I now think that an ASIC-optimized mining algorithm is much more secure than a CPU-optimized one. You can rent a supercomputer or retask a botnet to attack a currency whose PoW algorithm works best on an ASIC.

Thanks David, though I find it intriguing. If you can repurpose a botnet or a supercomputer's timeshare to attack an ASIC/GPU friendly crypto-currency, how does that make it more secure than a CPU-friendly crypto-currency? Besides, both a botnet and a supercomputer could be used to mine scrypt-based currencies as well, and be very efficient at that...

You can't really repurpose a botnet or a supercomputer to attack an ASIC-friendly crypo-currency -- you pretty much have to invest in ASICS, and thus in the very crypto-currency you're attacking. That's why Bitcoin got it right.

The scrypt key derivation function was explicitly designed to be resistant to hardware optimization, with an explicit trade-off allowed between memory and cpu usage:

The scrypt key derivation function ... is designed to be far more secure against hardware brute-force attacks than alternative functions such as PBKDF2 or bcrypt.

This makes it better than SHA-256 or bcrypt if the intent is to give more of an advantage to CPUs.
Another option would be to include the same sort of variety of primitives that are provided for general purpose CPUs, e.g. a combination of floating point operations, access to large memories (perhaps including something that would use a large random access memory like a disk), etc.
But as Thilo point out, including some sort of anti-botnet feature might also be needed.  A CAPTCHA might also make it rather unpopular, but some sort of work load that would indeed be noticed by a regular computer user might make it hard to hide botnet activity.

Tenebrix is AFAIK the first crypto currency relying on CPU-friendly algorithms (specifically scrypt if I'm not mistaken). http://tenebrix.org/ Note there are some serious caveats with Tenebrix: https://bitcointalk.org/index.php?topic=47269.0

I think using a very large amount store would be interesting to explore. It would be very noticeable to a user, as "disk space left" is just about the only statistic they get. If that size is deduced from something difficult like the (high) primes it can be enlarged and shrunk as needed by the network. Interesting idea.

I suggest bcrypt. It is not a cryptographic hash function per se, but it could replace SHA-256 and add some memory constraints that would make its implementation harder on GPUs.
Bcrypt uses blowfish to encrypt a string with a key derived from a password chosen by the user. So given a string and a target, finding a password that encrypts the string below the target works exactly like the Bitcoin lottery.
As for the memory constraints, it is possible to implement bcrypt on a GPU, but it is much harder (probably impossible) to get the same kind of performance improvements we see with SHA. Here is an excerpt from a post on crypto stackexchange about implementing bcrypt with cuda:

Now bcrypt is a variant of the Blowfish key scheduling, which is
  defined over a table (a few kilobytes) which is constantly accessed
  and modified throughout the algorithm. Due to the size of the table,
  each core will have to store it in the GPU main RAM, and they will
  compete for usage of the memory bus. So bcrypt will run -- but not
  with full parallelism. At any time, most cores will be stalled,
  waiting for the memory bus to become free.

The choice of the SHA-256 algorithm for Bitcoin's proof of work has created what could be described as the most ideal application for botnets that one could possibly conceive of. Bot masters are looking for ways, essentially, to turn computation into cash. Bitcoin does that natively.
The huge risk is if the botnets take over the network. Given that botnets can comprise up to millions of machines (at their largest - most are much smaller than this), even with CPU mining a single botnet could potentially take over the network. For instance, assume a 2M strong botnet comprising Core2 Duo machines (5 MHash/s). This network would do 10 THash/s.
The only countermeasure to this is to have special mining gear that is more efficient than CPUs and GPUs, and not available on the average botted PC. This is why the community needs an ASIC-based mining solution.

Sure, if you assume someone makes the ASICs available to all rather than keeping them to themselves.

There is no 2 million strong botnet.  Anywhere.  Storm Trojan is the largest known botnet and it has 250K nodes.  The second largest botnet has a mere 30K nodes.  SHA-256 is the algorithm that is used and to say it is "ideal application" for botnets is silly.  The very fact that GPU can efficiently accelerate SHA-256 is what gives bitcoin a chance against botnets.  Since 1 high end GPU can equal 200+ CPU it gives the "valid nodes" a multiplier effect.  Even if your unrealistic example 10TH botnet wouldn't have sufficient capacity to break bitcoin.

@DeathAndTaxes How do you know the size of various bot nets?


text:
Can the blockchain be included in future packages of the standard client?
Is it possible to include actual transaction history to new version of Bitcoin client?
I mean, when someone new downloads a fresh version from http://bitcoin.org.
It is very hard to get more people into the Bitcoin community, when the start takes sooo looong.
(It looks like it never ends, like a bug.)

You can download the transaction history separately (don't have the link on me currently). Adding it to the client would also be disencouraging - 1GB of a "program" doesn't appear too user-friendly.
Alternatively, one can use a lightweight client (like Multibit or Electrum), or an eWallet (like StrongCoin).

Oh ... 1GB .. it is not simple to start with bitcoin.
Will this transaction history consume my whole disk space, when more and more people join bitcoin society?

@Peter - Eventually most normal users will not use full clients, only miners. Most users will use thin/web clients instead.

@Peter I'm guesstimating it might hit 2GB tops by the end of the year, so it's not too bad. My windows updates leftover files were about 10 times that amount after a couple years. By that time someone will probably make a decent client that prunes old data (if you really want to be connected to the Bitcoin network). Otherwise, use web/Stratum clients.

The project is essentially in a beta phase. People who run the Bitcoin client now are typically the highly technical early adopters who will build the next layer of software and services on top of the basic Bitcoin protocol. Those services (exchanges, banks, payment gateways, thin clients, trust networks, laundromats, ...) are what ordinary end-users will adopt en masse.
So I believe the answer is no: the Satoshi Bitcoin client will never come with the blockchain included, simply because the target audience are not the kind of end-users that find a large initial download a problem.


text:
How are some coins premined?
Did the developers of the various premined coins have to wait for those coins to be mined first or did they change the code to first issue themselves the premined coins?
I'm referring to the list of coins at http://altcoins.com/scamcoins

Both options are possible. I don't know how most scamcoins do it but I believe it's more common to actually mine coins before the chain is released to the public.

They can mine with low difficulty first and then raise it.

There are various ways to premine coins, some are use for scam coins and others are used by experimental altcoins.
The premining made by scam coins are usually made with 3 methods:
1-At the first method the guy create the coin and start to mine it, after some amount of time he tell the internet the coin exist and promote it. At this moment he already have alot of coins. After it, he sell the coins he has to the public.
2-The second method involves the guy promoting the coin, but just creating a thread about the coin at some forum and not really advertising it, he just start to really advertise the coin after he has already mined alot of coins. The difference between this and number one is that this method will reduce the amount of people that will say the coin is a scam. After people start to mine the coins, he can see the coins to those who want.
3-The third involves selling all the coins to the public, everyone pay some amount of money and each person that gave money to the project get some % of the coins based at the amount of money they paid to the developers. After they receive the money, they gradually stop to work at the coin. Mining is made to get transaction fees.
Then there are the other premine method, used by experimental coins, some say some (or all) of those ideas are bad ones, but they aren't made by people trying really scam others, but by people that want to try the idea or think they can work.
1-The previous idea 3 can be used in a non scam coin. If that's the case, the developers will really continue to work at the coin, after they receive the money.
2-Another method include burning coins. People sent another altcoin (at some implementations a specific coin, at others various coins can be burned) to a place that will then (at the moment they sent the coins or at a specific date) burn their coins. The users that burned the coins will receive money from the new coin based at the amount of coins they burned. They can either receive X coins for every Y coins their burned, or Z% of the total amount of coins based at the % of total burned coins that came from him.
3-Other method includes, sharing the coin equally between everyone that ask. When the coin "start to run" everyone will have their own coin.
4-This fourth method involves people mining the coin as usual, but the coin is blocked, you can't use the coin until all coins are mined.
5-At the fifth method, people don't mine coins, but they mine numbers. People use their computers to mine numbers and after some amount of months or years the mining stop. After the mining stop, all coins are spread between the users, based at the amount of numbers they mined, if there are 100 coins and 3 users mined numbers, the first one mining 30 numbers, the second mining 50 numbers and the third 120. The first guy will get 15 coins, the second one will get 25 coins and the third one. will get 60 coins.
At method 3 of of scam premine and all the 5 method of non scam premine you can either have transaction fees, where people mine those fees, or demurrage, where the system get X coins (or X% of your coins) every Y months and give back to the system to be mined.


text:
How can I buy Bitcoin via a Credit Card or Paypal?
I want to buy some bitcoins. Ideally, I would like to buy them on the MtGox exchange (because the consensus seems to be that this is the most reputable exchange), however I have found the system for transferring USD to MtGox to be very disappointing. I would have liked to be able to add funds with PayPal or directly with a credit card, however both of these are not possible.
My question has two parts:

Is there an easy way to use a credit card to add USD funds to my MtGox account. Liberty Reserve, Dwolla, and Paxum seem to be the financial institutions of choice for MtGox and the rest of the exchanges. Is any of these simple to fund using a credit card, or are they all basically PayPal analogues (which Paxum seems to be) that require a large amount of setup?
If it is not possible for MtGox, is there another, hopefully reputable, exchange that I can use PayPal or a Credit Card to buy bitcoins with?

You should be able to send money by credit card via Western Union to one of the services supported by one of the bitoin exchanges. It's impractical and the fees will probably be high.

Related question: http://bitcoin.stackexchange.com/questions/91/how-do-you-obtain-bitcoins

related: https://bitcoin.stackexchange.com/q/5465/5406

Read the comments on answers - some things have changed.

I did some more digging on bitcoin.it and answered my own question. According to the FAQ and the list of payment methods, the reason that Paypal and Credit Cards are not accepted is to prevent fraud (by doing a fraudulent charge-back). For this reason, none of the exchanges accept these as forms of payment.
In short, you cannot (directly) use these to buy bitcoins at exchanges.
Edit: I did have some luck buying some Bitcoins using Paypal using #bitcoin-otc. It takes a bit of setup and it's a bit more expensive, and you can't buy in significant quantities but it's possible you can find someone willing to sell to unrated users (liked I did).

This is simply incorrect today speaking from 2018.

I noticed this question was posted a long time ago and perhaps things have changed so I took the liberty to dig in again and also aggregate most of the answers given here and here’s what I found:

It’s indeed impossible to buy Bitcoins with Paypal DIRECTLY even today and it's mainly because of Paypal’s TOS (Section 3.7 here) and the issues of chargeback.
Having said that there are still a few ways you can buy Bitcoin with Paypal
a. Use VirWox to buy SLL with Paypal and then transfer that SLL to BTC (has high comission, transaction can take between 1 hour to 2 days). The full process is explained here.
b. You can use Local Bitcoins and perhaps find someone in your area to sell you Bitcoins with cash or even someone not in your area to sell you Bitcoins with Paypal or a credit card.
c. If you’re only into trading Bitcoins for their volitility and not actaully keep them you can use platforms such as AvaTrade or Plus500 to trade CFDs. However CFDs are for more experience traders and your capital is at risk so take that into account.
d. If you have a Paypal Debit card you can actually connect it to your Circle account and use the funds on your card to get BTC. This is relevant to US residents only.
Same thing goes for credit cards. Because of chargeback issues there’s no direct way to buy Bitcoins with them. Currently some options for credit cards are CoinMama, Circle or Cubits.

Maybe they should've called it a BitBlock instead of BitCoin.  If I'm looking to buy 1 bitcoin, currently, it's "selling" for $395+.  What can I get for $100? BitGrain?

Under the current PayPal TOS applicable here it IS possible to buy/sell digital currencies with Paypal so far as I can determine. AND buyer protection is NOT applicable. (sorry for the caps)  https://www.paypal.com/au/webapps/mpp/ua/useragreement-full

PayPal's user agreement prohibits the use of their payment network for buying digital currency.
Here's an approach.  With VirWoX you can buy SLL and pay with either credit card or Paypal.  Then you can trade your SLL for BTC:

http://www.VirWoX.com

Sporadically you will find inventory on BTCQuick:

https://btcquick.com

And finally, there is the ability to deposit cash at a bank (presuming you are in the U.S.), so the need to use something like PayPal has lessened.

http://www.bitinstant.com

If you are a U.S. citizen and don't mind going through an ID verification process, you can buy bitcoins and litecoins instantly with a credit card at

http://www.coin.mx

Yes and they have 8% commissions.  5% to buy and 3% to sell.  (I don't know why they just don't have 4% either way.)

You can fund bitcoins with ACH (bank) using coinbase.com

You can also transfer USD to VirWox via Skrill Moneybookers (CreditCard) and then buy SLL...

May have been the case, seems it no longer is under the TOS applicable here: https://www.paypal.com/au/webapps/mpp/ua/useragreement-full

Buying bitcoins for credit card or PayPal is very problematic, but all hope is not yet lost.
Every now and then a new service pops up that thinks it cracked the secret of how to do this sustainably - http://www.mrcoins.org/ seems to be the flavor of the month. Such services usually take a very high fee.
CoinPal was a great service when it ran, and they said they're considering returning with credit card payments. They know what they're doing so they may actually pull it off.
Also, http://www.memorydealers.com/ sell casascius physical bitcoins which you can buy and redeem (or not).

I strongly recommend not using such services. They are doomed to fail for a very simple reason -- they have to charge high fees, legitimate users are generally not willing to pay high fees, but scammers always are since it's not their money. Thus most users of such services will inevitably be scammers, and the business will collapse -- possibly while holding your money.

@DavidSchwartz - good point. http://en.wikipedia.org/wiki/The_Market_for_Lemons

@DavidSchwartz: I understand your sentiment but I'll have to disagree. First, because these transactions should complete in a matter of minutes, and the chance the business will collapse with your money in a few minutes is slim. Second, because this doesn't apply to services which know what they're doing - CoinPal with its anti-fraud mechanisms offered reasonable fees and did not have a problem with fraud, only with PayPal freezing.

They should complete in a matter of minutes. Whether they will when the company is collapsing is another story. CoinPal succeeded for a time because they made PayPal deal with the fraud, which of course is something PayPal is not willing to do. You can only pass your costs on to someone else for so long. The fact is, it costs more to support reversible transactions and that cost will have to be passed on. Honest customers have no reason to pay that fee. Fraudsters have no reason not to. I think this is an inherent problem.

PayPal forwards fraud costs to the merchant, they don't absorb them. CoinPal succeeded and had very few chargebacks because they had heuristics to identify suspicious customers. PayPal froze their account because of their policies, not because of fraud.

Mr. Coins has been "out of stock" for some time.  Still out.

PayPal froze them because of their policies, sure, but their policies are to combat fraud. As for CoinPal -- I wonder why he hasn't re-opened accepting Dwolla. I think he'll find, sooner or later, that the fraud destroys him. There's just not enough money in there to cover the fraud costs.

[Update: This exchange method is no longer available.]
a website with the url of http://www.iocoloradocentral.com/ has converted my paypal funds to bitcoins for quite a while now, i have always received the bitcoins :).

You can buy small numbers of Bitcoins with a credit card at http://www.buybitcoinswithacreditcard.com/ (or at least, you could as of March 21, 2013).

Looks like a parked domain now.

You cannot turn paypal into bitcoin but you can do it the other way around.
Check out this site:
https://www.bitinstant.com/
They accept cash deposits (US only) and are also supposed to speed up the different transfers they allow. For example, from dwolla, paxum or liberty reserve to mtgox or tradehill. I haven't tried it myself though.

Not really an answer, should have been a comment - the question is about buying, not selling.

btcnow.net Sells via OKPAY which is a Russian PayPal analogue. Like PayPal, it allows you to directly fund a transaction from a credit/debit card.

I know https://metabank.ru/buy, a Russian exchange service with a good reputation (tracked on various bitcoin-forums).
There, one can

buy bitcoins for qiwi, a Russian payment system (where your account is identified with your mobile telephone number, and you can choose to confirm your payments through your mobile phone),
and one can pay in qiwi with a VISA/MasterCard (you have to register your card as a payment method beforehand, and validate that you own the card by providing to qiwi the information about a random small amount that has been blocked on your card by qiwi for a short period of time).

Qiwi charges 0.75% for payments with a card, and Metabank charges 4% commission for such an exchange (the exchange rate is the current price at MtGox).

As for now, I can't open this site. (Probably, it closed down quite a while ago, because this business became too dangerous or tricky from its owner's point of view.)

wesellcrypto.com
best site if you want to buy btc with paypal
www.virwox.com
most reliable site to buy btc with paypal. cons: expensive! more than 20% fees
coinbase
Low fee for PayPal, only in the US

Uhh.. Purchasing disabled - Unfortunately we are currently having some funding issues, any orders that have been placed will get processed. Site will come back up when funds arrive, so I think not so good.

they are the best when it comes to paypal. yes the are currently down due to a high amout of users

How can the be the best if you can't use them?  Also, did you not notice the word "reliable" in the title?

its working 99% of time since a week. sad thing is that there are no alternatives to to buy btc with paypal except virvox and wesellcrypto

Welcome to Bitcoin.SE! Your answer was moved to a canonical question due to its original parent question being a duplicate. Please check if you need to update your post to make it a good fit on this topic. Thank you.

You can buy btc with paypal on coinbase, so I don't understand why you say there are no alternatives.

10Btc for u when u find a reliable PayPal worldwide seller with lower than 15% fees.

Brawker solves this by letting you fulfill fiat currency orders for other people, which then release BTC for you upon completion of the order.

Since you are asking if there is an exchange that accepts PayPal -> Bitcoin the short answer is no. However; Localbitcoins is a great place where you can meet other buyers/sellers such as yourself who are willing to convert your Paypal funds to Bitcoin.
Make sure to look at the seller/buyer's feedback so to not get scammed. It is relatively safe, and is much safer now that PayPal acknowledges bitcoin and does not shut down people's accounts for using PayPal for Bitcoin related activities. For a great tutorial with a video on how to convert your Paypal funds to Bitcoin using Localbitcoin visit: http://www.btcfeed.net/tutorials/how-to-convert-paypal-to-bitcoin/

Coinbase is pretty much the standard most people use.  There are other sites, with varying degrees of reliability and legitimacy.  I'd stick with CB

Your answer was moved to a canonical question due to its original parent question being a duplicate. Please check if you need to update your post to make it a good fit on this topic. Thank you.

You can buy Bitcoin via credit card / paypal via https://xcoins.io
Disclaimer: I do work for them as an Software Engineer in our Santa Monica office.

Your answer was moved to a canonical question due to its original parent question being a duplicate. Please check if you need to update your post to make it a good fit on this topic. Thank you.

Sorry - you should explain better that the businness there is lending bicoins, not selling them.
Or at least update the FAQ and add optional buying transactions as valid - if they are valid.

I can recommend my favorite instant exchange https://www.247exchange.com/buy although they have quite strict verification requirements for orders paid by credit cards and order limit starts from $100 for first order, their rate is very good and their support is very helpful. It's rather new exchange, but it's run by financial company, website is PCI compliant so using 247exchange is a reliable way to buy bitcoins with credit card.

As of July 2018, there is no feasible way to purchase bitcoin or other cryptocurrencies with paypal and/or a credit card, other than potentially private party / localbitcoins.

Virwox Exchange is my favorite. I live in INDIA and we don't have Bitinstant support here so Virwox is the fastest and trustworthy option for me.
They do charge a premium, but you can always get a good price if you wait for a while before buying or selling BTC’s until the BTC exchange rates in the VirWox marketplace are within your target range.
For detailed instructions check here.

authors: Виктор Персиков


text:
Installing Bitcoin-Qt on Ubuntu
I am using Ubuntu 11.10. I have downloaded Bitcoin-Qt, but I don't think it has installed itself. The instructions say "download and install" the software, but I'm afraid I need instructions that are a little more specific. If you can tell me how to install the software it would be greatly appreciated.

You need to be more specific. Where did you get the software from? What steps have you done? etc

I got the software from this website (bitcoin.org). I downloaded it, but I'm not very knowledgeable about Ubuntu or programming. I found one page that gave me a string of magic jibberish to put in the DOS window, which I did, but it seemed to have no effect.

You're on bitcoin.stackexchange.com now, not bitcoin.org. I've edited your question to be more meaningful.

sudo add-apt-repository ppa:luke-jr/bitcoincore
sudo apt-get update
sudo apt-get install bitcoin

When I put in that second line of jibberish I get this:
E: Could not open lock file /var/lib/apt/lists/lock - open (13: Permission denied)
E: Unable to lock directory /var/lib/apt/lists/
E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied)
E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?
donnie@donnie-amdnew:~$
I frequently run into the permission problem. Apparently, in Ubuntu, you have to get permission to do anything.

second and third commands also need sudo

if it worked you should mark the answer!!


text:
iPhone app for bitcoin
What does BitCoin suggested is the best App for iPhone?

Which company? Open-ended recommendation questions are not quite suited to the StackExchange format. This question might be closed if you don't explicit what your specific needs are.

Bitcoin does not suggest anything, it is a currency and a project, not a person.
Generally, the choice of an iPhone app is limited by the factor that probably what you'd want to see the most, a wallet app, is not possible on iPhone due to Apple's restrictions.


text:
What benefit does bitcoin provide over using a credit card?
I am brand new to Bitcoin. I am retired investor.
What benefit would using Bitcoin have over, say, using a credit card, etc.? It appears that Bitcoin is primarily designed for businesses, buying, selling, and using Bitcoin as the exchange medium.
I saw a chart which showed the Bitcoin/USD value at approximately $32 and then dropped to $2 and now is back around $15 as of August 18, 2012.

Hi George and welcome! You should change the title to something understandable that sums up your question. Is your question simply what benefits Bitcoin has over credit cards?

The security model is different - with credit cards, you give private information to a merchant, and you need to trust that merchant to make charges correctly. Additionally, the private information that you give is exactly the same for all of them. This is why credit cards NEED a chargeback system.

@NickODell you provided one of the reasons but not the only reason. Some transactions require a chargeback (i.e. escrow) system, because some merchants give bad service and don't issue refunds when they fail to honor their side of the contract or generally accepted business practices in lieu of an explicit contract. Note, there is a VerifiedByVisa program, where the CVV2 and/or password is never seen by the merchant. Security (as differentiated from privacy) may not be the strongest advantage for P2P currency over the long-term.

I don't consider these to be competitors.
Credit cards are a convenient way of doing payment processing on top of fiat currency. Bitcoin is a digital currency on itself.
Sure, Bitcoin today can function as a very rudimentary way of doing payments (just like cash-via-mail can be), but it's not particularly good at it - all it provides is storing and transferring value. What I hope is that in the future it will become a platform upon which payment processors can build. Since the currency is already inherently digital, building a payment platform on top of it should be significantly easier. Furthermore, since it is decentralized, everyone has the ability to become their own payment processor (or bank...).

I upvoted, but I'm not sure they could not be competitors in some future scenario.

My list of advantages for Bitcoin over credit cards (and money transfers) are:

instant free registration, no id checks
(for merchants, their customers, "banks", or any type of user)
increased anonymity and control over privacy
no self-regulation1, no limits
no authority exists to report to tax and other authorities
greater security
lower transaction fees
available 24/7 on demand
irreversible transactions
global acceptance
e-wallet ownership card can be duplicated and backed up unlimited times

I think #1 - 4 are the most significant advantages. I elaborated on some of the reasons in comments below some of the other answers on this page. #5 would also be but the P2P systems are not theoretically secure against deep-pocketed attackers (e.g. a ruthless government perhaps China or other soon-to-be totalitarian state).
Disclaimer: I am not advocating tax avoidance, nor giving any tax nor financial advice. I am merely stating significant differences with which some people might think are advantages.
1 The P2P systems don't impose any regulations nor restraints on transactions. FinCEN's guidance (FIN-2013-G001) is that creating and using decentralized currencies for purchasing goods and services are not regulated as money transmitters, but selling the currencies is.

All those speculating on the appreciation of Bitcoin should take note that FinCEN classifies selling of decentralized currencies as a money transmitter activity and falls under their regulation. There are forms and compliance activities that must take place with sometimes dire penalties otherwise.

As a consumer, the choice of payment method comes down to a tradeoff between convenience and cost.  When a merchant offers credit card payment or cash, oftentimes customers will choose credit card or debit card because it is convenient and costs no more than when paying with cash.  The credit card issuer may even be offering a perk to provide incentive to pay using a credit card.
But that is really a subsidy as there are costs to the merchant when payment are made using credit card.  There are tens of billions of dollars that go to payment card networks each year.  Merchants don't actually pay this, they simply add the cost to their prices.
Some merchants either refuse to offer credit card payments, or they offer two sets of prices.  You'll see this at gas stations, where payment for fuel pumped at the lower price must be given in cash, whereas the higher price is charged when payment is credit card.
The reason this "cash discount" isn't seen more often is because credit card companies had built into their agreements a "no surcharge" restriction.  Thus you couldn't add the fee after the sale depending on which payment method was used.  In the U.S., the card companies were just forced to abandon that part of their merchant agreement.  So you may start seeing surcharges when you use a credit card (in states where that isn't prohibited).  This will likely push many towards paying with cash.
But cash is not always convenient nor cheap.  ATM fees can cost 5% to 10% for the smaller withdrawal amounts for many accountholders.  Merchants have losses due to employee error, theft and management of the cash.  An electronic alternative would be welcomed by both consumers and merchants, if the fees would be less.
So if your merchant accepts only cash or bitcoin, or csah, bitcoin at one price and credit card at another higher price, you won't be asking what benefit bitcoin has but instead you'll be appreciating how it is saving you money at every purchase.
Merchants also like bitcoin for additional reason.  There are no chargebacks, so if you as a customer are due a refund, the merchant would need to issue it -- versus today's fraud-laden method where the consumer initiates the chargeback, whether it was founded or not.
There are many other advantages to Bitcoin, included here:

http://bitcoinmedia.com/bulleted-advantages

You emphasized that Bitcoin transaction fees might be less than credit card, but this is not absolutely guaranteed going forward if there needs to be some way to insure enough mining for security when the debasement scales down over the coming years. You say that merchants don't like chargebacks, but you didn't mention that in many or most cases, customers like to have that option available (especially for big ticket items). I don't think you have presented the strongest advantage of P2P currency, which is privacy and no regulation. Could be very important with global capital controls coming.

With Bitcoin the user does not give out any sensitive creditcard information. Instead of giving out the information so the merchant can use this to withdraw money.
The user sends their money without giving out any information.
Thus there is no information for a hacker to steal or for an employee to abuse or sell.
This means that the network can have much lower fees. When you compare the fees a creditcard charges 100 000% percent higher fees per transaction than the Bitcoin network.
Another advantage is that its free to get a Bitcoin adress.
There is also a projekt in the work, that might make it possible to use a creditcard to pay with Bitcoins. Called Openpay.
So it might become possible to use Bitcoin at any shop that takes VISA/Mastercard.
But the real benefit is that the Bitcoins in a Bitcoin network only belongs to the owner controlling the adress.
As opposed to having the money in a bank, in which the money belongs to the bank.
What you see on your bank account is how much money you have lended out to the bank and for this they give you an interest rate.
Thus, Bitcoins is the only way to own your own money in electronic form.

You claim that owning a wallet with Bitcoin units is complete control ("only belongs"), as compared to a bank account. This is not true. As the question states, Bitcoin can also experience a "bank run" and the value drop from $35 to $2. As with a bank account, the Bitcoin owner only holds a claim on external assets. That claim is dependent on market conditions.

There are countless reasons why you should choose bitcoin over credit cards. Some are the following: 1) No Paperwork Involved-it does not ask for any identification information unlike credit cards wherein you’re required to input your address and contact details., 2) It’s Quick and Easy--generally confirmed within an hour or less, 3) Irreversible Transactions-only payment method that is 100% irreversible and cannot be charged back., 4) You can carry it anywhere-BTC can be store either in your desktop of smartphone; just scan the QR code and you are good to go.
Source: Bitcoin’s Advantages over Credit Cards--http://bitcoindaily.com/bitcoins-advantages-over-credit-cards/"

I am pretty sure there aren't countless reasons to choose Bitcoin over CC. ;) Anyway, I think you haven't read the other answers: 1)-3) have already been mentioned . And concerning 4) I fail to see how Bitcoin is more mobile than a credit card, especially if you store them on your desktop PC. Leaves me wondering, whether the main goal is to plug the website linked at the bottom.

authors: Николай Караджов


text:
Why not multiply "six confirmations" and divide Time-Between-Blocks and Reward by the same factor?
It seems that choosing a good factor to use to expand Bitcoin's capacity is a good idea.  The software would divide some of its calculated values by this factor, such as the target time between blocks during difficulty calculation, the number of blocks between difficulty adjustments, and the subsidy.  To achieve the security of "one hour's worth of hashing power," the recommendation for confirmations would be multiplied by this factor.  It seems that using a factor of two from time to time (whenever the community finds it valuable) would be appropriate.
Let's suppose we choose a factor N. This will allow the blockchain itself to grow N times as fast, providing N times the transaction fees to miners, multiplying the number of rewards by N (but dividing the reward itself by N), dividing the average wait for a confirmation by N, and multiplying the rate at which transactions are confirmed by N.  This also reduces the variance of mining revenue.
This allows time (instead of network bandwidth and computer memory) to be used to expand the carrying capacity of the bitcoin ecosystem.  Should such a proposal be written into a BIP?
The objections to this idea so far have been answered in the comments.  If anyone feels that there is an objection adequate enough to drop the idea, please post an answer.  If anyone wants to create a BIP, please let me know so I don't have to do it myself.  I don't mind doing it myself, but I'll probably be slow.

your suggestion also increases network bandwidth, as the time interval between blocks shrinks, the capacity required to propagate blocks increases. There's also a latency that comes into play. As time interval between block shrinks, the proportion of time contributed by latency increases and plays into higher probability of a minted block getting orphaned. Keen to hear what the others think.

So if N=2 we have a new 1MB block every 5 minutes instead of 10 with every miner reward halved compared to current protocol? Isn't this fundamentally the same as doubling the block size (albeit in a more convoluted way)?

One downside is that you have to get all end users to understand that the benchmark for number of confirmations has changed, and do it again each time N changes.  Under the current system, end users can memorize a magic number like 6 confirmations that will never change.  For such end users, a block size increase can be transparent, even if it's a hard fork; they have to upgrade their software, but they don't have to change their ways of thinking.

@renlord - yes, bandwidth requirement goes up with capacity.  Orphaned blocks go up too, but only cause half the loss they normally do.

@Sven-Williamson - yes, fundamentally the same, but doesn't double bandwidth for each block or the mempool load as blocksize increases do.

@Nate-Elderidge - The security should always have been "an hour's worth of hash power" and changing it to that is a fundamentally sound change.

@NateEldredge You could implement this as 'fractions of a confirmation.' So instead of seeing 7 confirmations under the new system, they would see 3.5. Problem is that you need all of the wallets to adopt this new numbering system.

related: Why is a short blocktime considered to be unsafe?, Why was the target block time chosen to be 10 minutes?, Which cryptocurrency has the smallest block time?, Would it be possible to make a functional Bitcoin fork that confirmed a block of transactions every millisecond?

In consideration of replacing the 1 block with N blocks in the same time frame, N > 1, I see the following points:
Advantages

Expected time until first confirmation is reduced
Mining revenue is distributed smoother among pools
Capacity of network is increased
Smaller peak traffic than increasing blocksize by N

Disadvantages

A hardfork is required to adjust the block interval
Increased chance of chain forks and higher stale rate due to block validation taking a larger portion of block interval
Thin clients need to store a larger amount of headers
Slightly bigger bandwidth usage than larger blocks

Still, it may be that 10 minutes is too conservative and a smaller block interval would provide an overall benefit. For example, at Scaling Bitcoin Milan, Arthur Gervais presented simulation results that he interpreted to suggest that Bitcoin could safely use 1 minute blocks.
CoinDesk covered the topic in A Lower Block Time Could Help Bitcoin Scale, But Will It Work?.

How would the money supply be affected?  The proposal was to divide block time and reward by the same divisor, so the money supply would continue to grow over time at the same rate as before (though a bit more smoothly).

@NateEldredge: The money supply be very slightly reduced because block subsidies would earlier forfeit part of a satoshi per block when the halvening moves precision to decimals but only full satoshis can be paid out. – However, I just calculated the actual amount, and even for N = 10 it's just slightly less than 25 mBTC, so I've removed the mention from my answer.