text:
Why is 6 the number of confirms that is considered secure?
Why is 6 is the number of confirmations that is considered secure? I haven't found any mathematical explanation or otherwise that explains why it is 6 and not 5 or 7. Is there a historical reason for 6? Is there a specific way to calculate it so 6 is just a number that was chosen?

Here are some of the relevant sections from Satoshi's paper:
http://bitcoin.org/bitcoin.pdf
"11. Calculations
We consider the scenario of an attacker trying to generate an alternate chain faster than the honest chain.  ... The race between the honest chain and an attacker chain can be characterized as a Binomial Random Walk.  The success event is the honest chain being extended by one block, increasing its lead by +1, and the failure event is the attacker's chain being extended by one block, reducing the gap by -1. ... The probability of an attacker catching up from a given deficit is analogous to a Gambler's Ruin problem. ...
p = probability an honest node finds the next block
q = probability the attacker finds the next block
qz = probability the attacker will ever catch up from z blocks behind

Given our assumption that p > q, the probability drops exponentially as the number of blocks the attacker has to catch up with increases.  With the odds against him, if he doesn't make a lucky lunge forward early on, his chances become vanishingly small as he falls further behind ... the attacker's potential progress will be a Poisson distribution ... To get the probability the attacker could still catch up now, we multiply the Poisson density for each amount of progress he could have made by the probability he could catch up from that point.
Converting to C code..
include <math.h>
double AttackerSuccessProbability(double q, int z)
{
    double p = 1.0 - q;
    double lambda = z * (q / p);
    double sum = 1.0;
    int i, k;
    for (k = 0; k <= z; k++)
    {
        double poisson = exp(-lambda);
        for (i = 1; i <= k; i++)
            poisson *= lambda / i;
        sum -= poisson * (1 - pow(q / p, z - k));
    }
    return sum;
}

Running some results, we can see the probability drop off exponentially with z.
"

Could you summarize the relevant part?

The conclusion is that the probability of someone being able to generate blocks drops off exponentially. We know they can in fact do this if they have 51% of the network. So it seems that if someone had say 10% of the network, they could pull off a double spend sometimes with 0 confirms, and the odds of them getting 2 blocks, or 3, or more...drops off exponentially.  This is how I am interpreting this, I don't understand in detail the math he solves for. Im still not seeing any rational for 6 blocks, as opposed to 4 or 8. Perhaps there is non, and this was just a nice number that was picked.

With 30% and 6 blocks the probability of success is much higher than 1/2000, it's closer to 13% (I'm interpolating from Satoshi's results).

@MeniRosenfeld Crap your right.  I looked up wrong value.  I am deleting my prior comment because it is factually wrong.

I believe this is addressed in page 8 of Satoshi's Bitcoin paper when showing the probability of an attacker catching up.
The wiki states:

"Only 6 blocks or 1 hour is enough to make reversal computationally impractical."

The key word is "impractical".
The important sentence in Satoshi's paper is:

"Assuming the honest blocks took the average expected time per block, the attacker's potential progress will be a Poisson distribution".

So, it is not that someone couldn't create the worlds first and own a $50 million ASIC farm, so as to have the ability to overtake the blockchain from a fork six blocks prior but that doing so would be a.) a massive undertaking, b.) obvious to all and c.) terrifically unprofitable to the attacker.

It's also noteworthy that it's largely understood to be "6 blocks or 1 hour" whichever is greater. One of the big misconceptions we've spent a long time fighting (especially in the case of alternate blockchains) is the idea that faster confirmations change anything. A network with a one-minute block time would require 60 confirmations to be considered secure, not 6.

That helps some, but it opens up another question. Why is it that 1 hour is expected to be enough to make reversal computationally impractical?

There's a lot of math behind it, but in my (limited) understanding the key is the Poisson Distribution bit. The chances of a modestly armed attacker getting "lucky" and successfully double-spending without having at least 51% of the network falls along such a distribution, and 60 minutes of computing time is the point at which it is adequately unlikely that a transaction may be undone (i.e. the point where the "long tail" of the distribution begins).

David, I'm afraid you're the one who has a misconception. The math parts which relate to the Poisson distribution and such talk about number of blocks, not time. 6 blocks is what guarantees that someone with, say, 10% of the hashrate, has a negligible chance to succeed double-spending. If each block is 1 minute then that's 6 minutes. The time (1 hour) only matters if we assume the attacker can't maintain his high hashrate for that long.

should I assume that David is correct rather than Meni since he's received more votes?

@Griffin: Have a look at https://bitcoil.co.il/Doublespend.pdf and judge for yourself.

Many people misquote Satoshi paper and assume 6 is some hard value.
Satoshi's paper outlines the number of confirmations necessary to be 99.9% sure (less than 1 in 1000 chance of success) that an attacker couldn't build a longer chain to reverse the transaction.
http://bitcoin.org/bitcoin.pdf
P < 0.001
q=0.10   z=5
q=0.15   z=8
q=0.20   z=11
q=0.25   z=15
q=0.30   z=24
q=0.35   z=41
q=0.40   z=89
q=0.45   z=340

p is the chance of attacker eventually getting longer chain and reversing a transaction (0.1% in this case).
q is the % of the hashing power the attacker controls.
z is the number of blocks to put the risk of a reversal below p (0.1%).
So you can see if the attacker has a small % of the hashing power 6 blocks is sufficient.  Remember 10% of the network at the time of writing is ~100GH/s.  However if the attacker had greater % of hashing power it would take increasingly longer to be sure a transaction can't be reversed.
If the attacker had significantly more hashpower say 25% of the network it would require 15 confirmation to be sure (99.9% probability) that an attacker can't reverse it.
If the attacker has q of >50% ("the 51% attack") then given unlimited time the attacker will inevitably end up with the longest chain.
On edit: to clarify the "unlimited time" the chain with the higher hashrate will inevitably end up the longest however probability still comes into play.  We can not say with 100% certainty how long it will take at best we can provide a confidence interval.  If the attacker is just barely faster than the good miners (51% vs 49%) then it can take a very long time for an attacker to overcome a deficit of 6 blocks.  The more the attacker dominates (i.e. 70% vs 30%) the quicker the shorter the 95% confidence interval is reached.

If the attacker has a q >50%, he needs not unlimited time, but only enough time to produce more hashes than those contributed to the "honest" blockchain.

My point with unlimited time is that we don't know exactly how long it will take for an attacker to pull ahead.  Even with >50% of the hashpower the attacker is still affected by luck (good or bad).  The most that can be said is with a certain confidence interval.  i.e. "With 95% confidence, an attacker with x% of the hashrate will have the longest chain after y blocks".  At just above 50% hashrate the amount of time to have a 95% confidence is very long and even that isn't a guarantee.  The chain With >50% hashrate will inevitably end up the longest but the time required is probabilistic.

It is basic probability, I would call it math more than a theory however one could observe it using a Monte Carlo simulation.

The figure of 6 blocks is completely arbitrary. It is based on the assumptions that the attacker will not amass more than 10% of the network hashrate, and that a negligible chance of 0.1% for successfully double-spending is acceptable.
A more detailed analysis of this is available at Analysis of Hashrate-Based Double-Spending

With more confirmations probability of making a successful double-spend decrease. While it is possible to perform a double-spend with less than 51% of hashing power it requires one to be luckier than the rest of the miners, ie. solve blocks faster than others. This will go on forever (to be correct: it is very unlikely) so the attacker will not be able to fork the whole chain. With pools until very recently controlling 30-40% of total hashing power the 6-confirmation rule would not have been safe if the pool operator had decided to commit a malignant act.


text:
Is there any tech that uses a signature as a private key?
I've been pondering how the Lightning Network will work when one of the parties in a channel tries to cheat.  It seems that publishing a transaction that shouldn't be published (a "bad act") must involve publishing something the victim can use to unwind everything.  I'm trying to identify what it is that the bad act provides to the victim, the "signature as a private key" seemed like a possibility.
Even if the "signature as a private key" idea isn't used in LN, it seems like a useful concept, but I couldn't find anything on the internet discussing it.  I tried a Google search and then came here.

Pretty much any data can be used as a private key.  In most cases, it is pointless and/or dangerous to use anything other than random data or a cryptographic hash of random data.  I don't understand what you are trying to accomplish, how specifically you would use a signature as a private key, nor how that would help.

I've shortly described how cheating is countered in Lightning network on How does the Lightning network work in simple terms?.

It seems that publishing a transaction that shouldn't be published (a
  "bad act") must involve publishing something the victim can use to
  unwind everything.

Really, I should have asked the question that Murch answered for me (and the LN paper also answers it, but I didn't read it carefully enough the first time).  That question is: "Does LN use signatures as private keys?"  The answer is no, it uses the existence of UTXOs from obsolete transactions as the information published by a cheater to defeat the cheat.
Thanks to Murch's explanation, and the link Nick provided to the LN paper, I can answer my own question.  There is a scenario I now understand better, so I'll mention it below.
In fact, the bad act itself is publishing an "obsolete" transaction that puts (some) bitcoin into each party's address, but from which the cheater can't spend for a while.  The existence of that transaction in the blockchain is what the victim can use to unwind the bad act.  This is the case because the victim, according to the way LN works, will have an "anti-cheat" (Murch's term) transaction from the cheater, already signed, which spends the cheater's output from that obsolete transaction.  It's a useless transaction unless the obsolete one gets broadcasted, and once that happens, it becomes useful and will end up sending most of the funds to the victim.
This may seem to provide the cheater with a "double-spend" opportunity.  The bad act (publishing the obsolete transaction) creates an output (the cheater's output) that the anti-cheat transaction is supposed to send to the victim.  Couldn't the cheater make their own transaction that also spends that output, but provides a high fee to reward miners for choosing to help the cheater?  The answer is no, the cheater can't make such a transaction because the outputs from the obsolete transaction require signatures from both parties.  The cheater already signed the anti-cheat transaction.
On the other hand, regarding the question I actually posed, I think the answer is NO, there is currently no tech that uses a signature as a private key.  Perhaps this is for the reasons Nate gave in his comment, or perhaps no one who could appreciate the benefits of doing so has thought of it yet.

What you're describing isn't really a public key/private key system. Public key cryptography was invented to allow you to give someone the capability to authenticate a message from you without giving them the ability to forge messages from you.
Creating what you're after is much simpler. Imagine the following scriptPubKey:
OP_SHA256 <32 byte hash> OP_EQUAL

To spend this, you would supply a 32 byte value that hashes to the hash in the contract. If you spent it, everyone would see the value needed to spend it.
See also the lightning paper.

source: Stack Exchange

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

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

sort: votes


text:
How to generate BIP85 Child Key using Bitcoin Explorer?
I've playing with 2 tools:

Mnemonic Code Converter (site)
Bitcoin Explorer (CLI) - bx command

For the purpose of test I've used these tree BIP39 mnemonic words: client mixed great.
Using a site I've created successfully BIP32 Root Key using above words which matches bx output:
$ echo client mixed great | bx mnemonic-to-seed | bx hd-new
xprv9s21ZrQH143K3UX3BhXusdpBUSLW3KVBCV6DGAuAKoXumU9chwDWjT9gcxjyFs8YdBxysyvZx2yC6snUBhb46wwXeq5xNqRjx5WkD8bbxYf

However when I'm trying to create a matching BIP85 Child Key (in Xprv format), it doesn't match:
$ echo client mixed great | bx mnemonic-to-seed | bx hd-new | bx hd-private -i 0
xprv9v6WUZT3D9NryJcPMGBxrauhE42egVktC9mwLKFuZUjinZencdiZ21d43oye8rX83cEjfAKptfaoceUYctptAhc2UUM398Akf9n6qXzd8RQ

$ echo client mixed great | bx mnemonic-to-seed | bx hd-new | bx hd-private -i 0 -d # a hardened key
xprv9v6WUZTBYouqAnZyHm1P76SvmRrmpvteFo2PhncirF6BNj2kr6qzTRJzJ41a5wwWKf35AjwtxDJEJ2U72H9g4LGj38Ytg2SzEfTQDVhEWB3

as the site reports the following key (in Show BIP85 section, app format: Xprv, index: 0):
xprv9s21ZrQH143K3ke8WGywxcKxZQuH5p3FMzZRFiGawhHo7Nt58HpBpoHv4fZM2a1n2cxgMWipEfJ6XaaGi8pW9pEmjnigzNBVJGQSNwwGuqp

What I am missing?

Are you sure you understand what to look for?
Not many tools have implemented BIP85
Pretty sure Libbitcoin-explorer (bx) is not one of them
Besides the iancoleman app, I only know of Coldcard & AirGap Vault.
See the spec for libraries
Python library implementation: https://github.com/ethankosakovsky/bip85
JavaScript library implementation: https://github.com/hoganri/bip85-js
https://github.com/scgbckbone/btc-hd-wallet

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


text:
Is there a webpage showing some of the latest orphaned blocks?
Blockchain.info has a couple pages about orphans, but the chart page does not agree with the list page.
My admittedly brief search for a page that shows orphans didn't turn up anything that was useful, so I'm hoping someone has one.  It seems a valuable resource for anyone involved in a trade where one side claims that the payment was confirmed and the other disagrees.

Just curious: Why do you think it would be valuable in payment disputes? A transaction’s presence (or not) in the longest accepted chain is ultimately what matters.

@chytrik I think it would be valuable in any disputes that arise out of a reorg for the party sending the payment to provide the intended receiver with a link to it with an explanation  It's educational.  Also, waiting for a payment that never comes can cause stress that is often relieved when a good explanation is provided.  I LOVE curiosity, so thanks!

When a block is orphaned the transactions are returned to the mempool unless they are already included in the longest chain.

If you're looking for an absolute authoritative source that will show you latest orphaned blocks, its impossible and anyone that claims otherwise is scamming you.
Why?
The Bitcoin network is a fully decentralized peer-to-peer network, therefore in the event of a temporal split (i.e. two blocks of the same height racing in the network), a block-tip that was accepted to extend the canonical chain will not relayed to adjacent peers (though it it is stored locally for record-keeping purposes). In that sense, it is only natural that no one can tell with absolute certainty of the existence/or the non-existence of the latest orphaned blocks.
You can increase your likelihood of capturing all orphaned blocks by sampling across more nodes that you personally run. But the only way for you to get the them with absolute certainty is for you to own the entire network -- which is impossible.

Good info.  I adjusted the question to attract helpful answers.


text:
When will FPGAs and ASICs 'replace' GPUs for mining?
Please explain in detail, or provide an an estimate, at least.

FPGAs won't.  ASICs will.

Currently the hash rate is around 25 TH/sec.  It is expected that when the ASIC hit the market in Dec 2012, the new hash rate will be about 250 TH/sec.  The difficulty is directly proportional to the hash rate, so it should also increase 10x.  This would reduce the profitability of existing GPU miners by 10x.  Plus about the same time the block reward will be halved from 50 BTC to 25 BTC, again halving the profitability.
The expectation is that once ASIC takes hold most of the GPU and FPGA mining will bleed out of the network.  You should expect to see an initial influx of ASIC and then a steady growth as mininers reach for their larger share of the market.

Within months of the arrival of the first ASICs, we should see the mining difficulty rise so high that GPU mining is completely irrelevant. ASICs are up to 100s of times more power efficient, if you believe the numbers circulating around the forums.
Why months? It will take time for the first units to be shipped, installed, and to begin mining. But I know that several groups have invested heavily in up front purchases of ASIC miners, so the ramp ought to be steep.

How much in dollars or Mhz is "heavily"?  I'd like to gain a relative perspective...

At the current exchange rate, GPU mining can still be profitable if electricity is below twenty cents per kWh.
In less than three weeks, the daily mining revenues will drop by half in an instant (the block reward subsidy "halving" event, around November 29th).  Difficulty may drop also as many GPU miners quit, but not much.  So the breakeven for electricity will probably be about ten cents per kWh.
If you are a GPU miner and pay more than seven cents per kWh, continuing to mine will either be a waste of time (not profitable) or money-losing (if you pay above ten cents per kWh).
From there, ASICs will push the breakeven for GPUs down further ...  to where the few people paying three cents per kWh can't even mine on GPUs profitably.
But since we don't know the future exchange rate and ASIC shipping dates and quantities, none of this is more than just being general educated guesses.
The halving event's magnitude (50 to 25) and time (around Nov 29th, 2012) is known.  That will eliminate a bunch of miners. Then for those still standing watch for when you start seeing ASICs shipped in volume.  Just know that is the point at which GPUs are then just a couple weeks, at most, from being obsoleted (unless you pay zero for electricity, but even then it is just a matter of time before you power them down for good).

I made some calculations and assuming difficulty will be increasing continuously at the average historical rate and hardware cost, GPU mining isn't profitable even for electricity rate 4 cents/kW. What GPU hardware do you refer to? Thx

profit has a great deal of factors such as the price of the bitcoin, energy costs and the scaling of the difficulty

It already has! Unless you are using Monero, ASIC mining has already dominated almost every coin and is hundreds of times more powerful and efficient.

Of course it already has. You are answering a six years old question.

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


text:
What GPU-APU configuration should I buy for mining Bitcoins?
I want to make own computer for mining bitcoins. I read a lot of it but I have some questions. I want to buy APU + Graphic card and I am wondering when I my computer is mining is using for that CPU + GPU(from APU) + normal GPU.
Can you tell me if this configurations is good?
Gigabyte GA-990FXA-D3 s.AM3+
ATI RADEON HD 5870
A8-3870K
DDR3 2GB CL9 1600Mhz
I will be running this on linux.
Every two months I will be adding one more ATI GPU until I get 4 of them. Is that good strategy?

Don't do this, GPU mining will be obsolete when ASICs are released.

So I'm too late? What type mining will be gaving profit?

Using dedicated mining devices with ASIC (application-specific integrated circuit) chips. The most well-known products are by http://www.butterflylabs.com/.

It's essentially too late to be worthwhile GPU mining because FPGA's are much more energy efficient, and cheaper to buy per unit of output. This has meant the difficulty has risen high enough that you won't cover the cost of your electricity (or your hardware) with GPUs. ASICs are likely to be shipped soon, which will largely make FPGA's obsolete. You can pre order ASICs from multiple manufacturers; Butterfly Labs is one.


text:
How does the network apply credit for created blocks?
First post.  I must say in advance thanks to everyone for all the great conversation and help and software so far.  It's really helped me get familiar with bitcoins and bitcoin mining.
I have a question about functionality of the Bitcoin network and how mining credits are applied to the correct person.
Assume a person is solo mining.  That is, one computer is doing the mining.  IT may be running a pool, but that's not relevant for this question.  So, lets assume a solo miner generates a few blocks and they get accepted.
When the network approves a block that has been created, how is the credit for the block creation (50 bit coins, soon to be 25) applied to the miner's wallet?
Let's say that a GPU miner, like DiabloMiner is running, and getting its work from Bitcoin-QT.  How does Bitcoin-QT, detect the mining credit of 50/25 bitcoins and send it to the correct miner's address?
Thanks.

Miner has to supply the Bitcoin address for block reward. Then, when the block is mined, the special "credit" transaction is permanently stored in found block, creating given amount (25 BTC, was 50 BTC) to given address.
Some pools (Eligius or P2Pool) use this feature and create a lot of credit transactions, so that when block is found, all participants will receive their respective share.

When creating a block, the first transaction in a block is always a coinbase transaction (a transaction with input of 0). In this transaction, the miner specifies output just like in a normal transaction - destination address, amount and so forth. This transaction is treated more or less just like every other transaction by the clients - it can be spent and so forth.


text:
How do miners receive transaction fees?
I know that in a transaction, the difference between the amount and the sum of the outputs is the implicit transaction fee, but how do the miners that verify the block containing that transaction actually get access to that fee as UTXO?

One of the network rules is that a coinbase's outputs cannot be larger than the current block reward plus the transaction fees of the transactions in the block.
So, a miner claims the transaction fees by increasing the amount of the block reward. This is true even after 2140, when there will be no block reward. (Network rules require that the first transaction be a coinbase, even if there is nothing to claim.)


text:
Which operating system would work best with pushpool?
Which operating system would be best for pushpool?

I use debian. But ubuntu or any other *nix OS would be fine.


text:
Mining as a screensaver
Strongly inspired by the SETI program, I was considering putting together a mining client that mines when a computer switches to screensaver. I know this would cost some PGU when the computer takes a nap, and would kind of defeat the purpose.
But would such a product be of interest to the bitcoin crowd ?
Would people be interested in a piece of software like this ?
I understand that serious miners would not be interested in this, but maybe, just maybe, the whole BitCoin thing would be easier to explain to some, if there was a piece of software that resembled the SETI program (which many people know or remember.)

I'd definately be interested in that.

I fear you would get barely enough bitcoins to make your effort worth it, let alone get enough to redistribute to the users... that said, it can be nice to do it just for the sake of it, if you feel to.

Also, I hope that using some of the matching techniques that SETI used, I can use it as a tool explaining the BitCoin system to more users :]

This question is phrased like a discussion, which isn't really a good format for this Q&A site. It might be better rewritten as "What are the pros and cons of..."

I have made my stack a bit more "discussion friendly"

There's a project on google code: http://code.google.com/p/miner-scr/

Heheh... nice. This was actually -exactly- what I had in mind :)

In the interests of keeping people's power bills low, I'd recommend not bothering to write anything that uses CPU mining as the bitcoins earned will not even come close to recovering the cost of the electricity.
If you can get it working with ATI graphics cards though, it would be quite a neat idea. It would also be a good way for charitable organisations to earn donations without people needing to put in their credit card details. Eg a donate-to-wikileaks screensaver.
However, there are also ethical issues to consider - not only does mining have a substantial electricity cost (where I live, it can be as high as $45 a month with my 5850 card), it also has a substantial effect of shortening the life of the hardware doing the processing. The average Joe Bloggs should really be made aware of those issues before they install & run mining software.

I agree. Most people would find the increase in power consumption costs more than they could make mining and the extra heat for long periods of time could well cause them real problems. I think the era of "casual" Bitcoin mining is gone now.

Casual mining is not too popular or profitable. If you are not mining casually, you mine all the time and don't want to slow your computer down with anything.
Moreover, one can set the priority of mining program to be quite low, thus not impeding the functionality of the computer (when computer is idle, computer mines at full speed, otherwise it slows down to let normal use have as much processing power as it needs).
Despite that. Some casual people might be interested in playing around with a screensaver miner if it was available.

There might be more interest for this in the sCrypt-based forks (the "CPU Friendly" forks) since they still have a fairly vibrant casual mining community.

@DavidPerry: those are toy-currencies, though.

Please be thoughtful with your comments @Lohoris, the URL may be "bitcoin.stackexchange.com" but the proposal was "Bitcoin & CryptoCurrencies." I know that bashing alternate forks is a popular pastime on the forums, but here it's inappropriate.

@DavidPerry: but they are toy-currencies. They serve no other purpose than allowing kids to "mine", for mining's sake.

@Lohoris: I'm not arguing with your point, I'm arguing with the idea that your point is appropriate for a StackExchange site. We welcome questions, answers and comments based on objectivity and facts, not opinions. If you want to share objective knowledge, SE is the right place. If you want to share your opinions, please do so on the forums.

@DavidPerry: I understand, but I think this is no opinion, I think it is a fact.

@Lohoris: The technology behind alternate cryptocurrencies is no different than the technology behind Bitcoin, the fundamentals of both are shared and only certain aspects of the implementation differ. Regardless, this is not the place for such an argument. If you asked "are the alternate cryptocurrencies 'toy currencies'" you'd be downvoted into oblivion and I think you're aware of that. Please stop.


text:
Largest current merchants accepting Bitcoin?
I am writing some rants about the use of Bitcoin, and would like to sum it up by naming some spearpoint examples of companies and service providers that use Bitcoin. Either solely or side-by-side with conventional currency.
But the few lists I came across were either hopelessly outdated or simply false.
Can anyone name me some of the top busters using Bitcoin ? Or maybe some good creative examples of Bitcoin use ?
And please not the Alpaca Socks site. I need some fresh examples to shake off a bit of the dust and make the article seem current.

The Bitcoin Trader lists top 10 sites that accept Bitcoin donations according to their Alexa rating - http://www.thebitcointrader.com/2011/12/bitcoin-bounty-ladder.html . But as those are donations rather than payments, I guess this is mostly a side-note on the major players that have anything to do with Bitcoins.

A not necessarily up to date list - https://en.bitcoin.it/wiki/Business_and_organizations_that_%22also_accept_Bitcoin%22,_but_do_not_revolve_around_Bitcoin

I just came by this question and think it is too localised. There is no specific timeframe listed, so the answer to the question is likely to change. No metric is specified for what defines a big merchant - is it the trade volume, income, number of people employed and so forth. Voting to close.

You are right, its a bit fluent question of mine, I was just trying to get hold of some "proof of concept" case.

The Bitcoin wiki contains a rather large list of companies that accept Bitcons. You can also add yourself to it once you started accepting Bitcoins.
The truth is Bitcoin is still in it's early days; soon it will be much easier to accept them.

One service provider that accepts bitcoins is NoTex.ch @ https://notex.ch: It's a browser based editor, that accepts donations - the donate button has been created using BitPay - or you can buy the full fledged offline version using a customized and very simple to use checkout process, which has been implemented using Blockchain.info's developer API:

Step 1) Enter your e-mail address,
Step 2) Scan the shown QR code for the actual transaction &
Step 3) receive the download link (within ca. one minute!).

Implementation details:
One interesting point of the transaction is that it's fully anonymous, that means NoTex.ch does not see from which bitcoin address the money has been sent. This is possible because Blockchain.info offers this great service, which mixes all coins being transacted to diminish tracing possibilities (more details can be found in Blockchain.info's API section).
Another effect of this mixing is that the customer is not required to wait 10 minutes for the actual BTC transaction to go through: Given that NoTex.ch trusts Blockchain.info, which sends immediately a notification upon a transaction to a target address, upon which NoTex.ch sends the corresponding email to the customer. This 3-way communication/transaction is usually done within a minute (if Blockchain.info's mixing bag is sufficiently full).


text:
Bitcoin as subscription method
I am contemplating designing some minor sites that uses bitcoins, but as far as I can see, a manual action is needed for every payment.
Is it possible to set up a "subscription" system or repeating transactions?
If not, I am planning to design a system where you can replenish your subscription, by simply "filling up" your account and then over time the allocated coins will be depleted.

Repeated transactions using Bitcoins is impossible, unless you have access to the private key. This requires a specific client. Such functionality is not yet available, as most people encrypt their wallets (the client can't decode it without the user. The second approach would be preferable.

That second approach could also be an external service, does not need to be tied to your site. Bitcoin wallet services could offer subscriptions just like PayPal does.

I have been buying subscription based services using Bitcoin payments delivered by BitPay.
You get a monthly invoice in email which you need to pay or the service stops working. One could automatize the processing of this invoice quite easily - after all Bitcoin is money with API (just pick up address, sum, automatize the send from your wallet). In this case, it would be the end user still in control what Bitcoin emphasis a lot.
The alternative, a prefilled wallet where you share the private keys and you can transfer Bitcoins back to yourself on any moment does not sound bad either.

"The alternative, a prefilled wallet where you share the private keys and you can transfer Bitcoins back to yourself on any moment does not sound bad either.". What do you mean? You cannot charge it back after the transaction has made it to the main chain.


text:
I didn't receive a Bitcoin Payment. What does it mean when the Client is synchronizing?
Bitcoin newbie here. I recently installed the Bitcoin client, and purchased some bitcoins from Mt.Gox. My problem is that my client is constantly synchronizing. I've checked charts and seen that my Bitcoins were successfully purchased, but my client seems to be stuck "Synchronizing with network". I've just got a constant loading icon in the bottom right, and when I hover over it it says it's "catching up". As I said, I'm new. Is this normal? Can someone explain what's happening? Thanks!

related: Cannot access my bitcoins because my wallet is still synchronising. What can I do to retrieve them?

This is probably normal. "Synchronizing with network" really means "downloading the block chain", and it can take a few hours to a day.
Following the "catching up" you should see the number of blocks already downloaded. At the time of this writing there are 220,000 blocks, when it reaches that you are fully synchronized. If the number keeps increasing you're probably on the right track.
You can speed it up a bit by forwarding port 8333 on your router (not very important, if you don't know how you don't need to bother).

That answer consider only incoming transactions. What about of the Outgoing transactions from Bitcoin Core Wallet? Is it the same OK to Send when the wallet not been synced?

@KursClub.com The question only asked about receiving transactions, not sending transactions.

Meni describes the issue well enough: Your Bitcoin Core is still catching up, and your incoming transaction will show up once the blocks that confirmed it get processed.
If you want to check meanwhile whether the transaction went through, you can use a blockchain explorer. Enter the address you gave when you requested the payment to see whether the transaction is visible on the network. You can find a blockchain explorer for example at blocktrail.com. Entering your address does not compromise your payment.


text:
Can gaming consoles be used as a Bitcoin mining platform?
I'm very new to the concept of Bitcoin (having only just read the wikipedia entry and visited bitcoin.org)
My question is this: why is the mining platform limited to PC/ traditional computing devices? It seems that gaming platforms would also work quite well, having better performance specs than the general user would reasonably have on his/her home PC and they have networking capabilities.

When CPU mining was common gaming consoles did provide comparable performance.  There was some development work for xbox360 and PS3.  However roughly a year ago GPU mining hit bitcoin network rendering CPU miners obsolete almost overnight. Using unified shaders in modern GPUs and OpenCL programming language GPU miners could operate in parallel working on many hashes simultaneously.  Even the earliest crudest implementations vastly outperformed any CPU in terms of raw hashing power, hashing power per dollar, and hashing power per watt.  Since then refinement of OpenCL kernels have only widened that performance differential.  Currently there is no economic value in using CPU for mining Bitcoins.
Due to the emergence of GPU mining there are a couple issues that make mining with current gaming consoles futile.

Marketing aside gaming consoles are not that powerful.  Today a $69 AMD graphic card has more computing power than either the Xbox 360 or PS3.  Moore's law is a powerful force and gaming consoles which were start of the art in 2005 are pitifully weak compared to hardware available today.
As already discussed CPU mining is futile and unprofitable
The GPU in both consoles while powerful at one time are rather lackluster by todays standards.  They could provide low end hashing power except they lack unified shaders which makes programming them to do hashing impossible.

Consoles are not upgradable and that is both a benefit and detriment.  Right now we are at the tail end of ther current consoles lifecycle and it works against using consoles for computing power.  Since they can't be upgraded they are essentially $600 computers based on hardware available in 2005.  However at the begining of a console life cycle the hardware is rather powerful for the price point and they are routinely subsidized. At launch a $400 xbox 360 contained about $500 worth of hardware.
So to answer your question there is no benefit to mining on current gen consoles, however it may be possible that "next-gen" console would be viable hasing platforms at least for the first couple years (before their static hardware fall behind due to the continually effect of Moore's law).
However there are some requirements for a future console to be a viable hashing platform:

The Console has a GPU with unified shaders and good integer
performance.
The ability to access those shader either through API (Microsoft
XNA) or hacking/rooting console.
Powerful GPU relative to retail cost of the machine.

It remains to be seen if future consoles could be used for hashing but using current generation consoles for hashing is simply not economical.

It would be awesome if you could update this answer for current consoles. It's probably way too early but can't even find any speculations on XBOX One and PS4 mining. Steam console probably has the most potential?

For now the platform is limited to whatever platform someone can run a miner on. For now, it is mostly PCs, but some people also mine on an FPGA board. Although some people looked at the specs of xbox, and they are pretty weak, similarly to PS3. Equivalent hardware was listed in the same topic, and you can see how they perform on the extensive wiki list of mining hardware.
So, whereas it is possible to mine on anything that can perform some basic computations, some machines are better than others. And with the profitability of mining being quite low, you wouldn't break even.

PS4 Pro Mines Neoscrypt at 1.4-1.6Mh/s . somewhere between 1080 and 1080 ti . though I wouldn't recommend it as Sony will send a firmware patch to brick your system.

Just so all you testers know. I finally got my PS3's to mine crypto besides litecoin and bitcoin. Unfortunately the hashrate through put isn't impressive like we all already knew. But I am confirming that I get an average of 80 H/S or so per system for Monero. Just in case any one was wondering since compiling any damn thing for the PS3 is usually obsolete these days. Especially alt-coins. So here is a work around.
How I did this: One must load NFS and SSH on the clusters nodes of PS3's with Fedora 9. Then one must have a linux capable laptop or desktop as their Master Node to compile and run OpenMPI. Which is open source cluster software. The PS3 can not compile alt-coin miners but will mine through OpenMPI and one's master node as a node on a cluster. So IT IS still possible to mine with them but the hash rate isn't remarkable. Any ways good night. I hope this will help some body and good luck! Can any one run a bench mark of Monero on their PS4 for me in the mean time? I would like to see if it is worth it to mine on the PS4 concerning alt-coins. Please and thank you.

I was told about Bitcoin a year ago by my friend, who is also a tech, but didn't know you could mine them.  I also thought it could be illegal, so I steered clear.
What I fear about using the consoles as a mining operation, is that the intellectual property rights are owned by the console manufacturers.  Want to run Linux to show that you can?  That's for fun and games.  If you make MONEY off of using your machine 'against the EULA (End User License Agreement), I imagine they could sue you or confiscate your Bitcoins.  This is just my opinion.

Rob
When or even if a cryptocurrency mining app appears on game system like Play Station, Xbox and others, the company who made the game console has allowed such activity and some companies will even encourage it. Besides that Xbox one CAN mine crypto coins, the apps though  have to be installed and running for XB1 to mine.
HOWEVER if the crypto mining app was forced onto the game system / game console by JTAG or other methods of homebrew / hardware or software hacking, you can get your game console somewhat unusable to fire bricked and your mined crypto coins lost forever due to being "confiscated", stolen or destroyed. Also when or if illegal activities happen such as, buying anything from the underground black market with your crypto coins, then you will surely lose your cryptoc coins and devices from the investigation of that activity.


text:
Should I use a different address for every transaction?
Should I use a different address for every transaction? If yes, why? For safety?
What happens I use the same address to get bitcoins from 2 different people, what happens?

The only reason why it is recommended to use a different address for every transaction, is for increased anonymity - it makes it more difficult to trace, and next to impossible to prove, that the recipient of transaction A is the same person as the recipient of transaction B.
If you publish an address to receive payments online, and keep it static, everyone can go to http://blockexplorer.com/ and see all the money you have received, and calculate how much money you got. If you change the address after every transaction, it makes it much more difficult - someone who have to constantly monitor your web page with the published address to know all your addresses you received money on. And if you keep the page with the published address non-public, such as that your customer has to log-in to his account on your system to see the address, that makes it practically impossible for third parties to monitor your income, find out how much money you have and what you spend it on.

OK, I get it. What happens if my computer will crash? Do I lose all my bitcoins?

That's a different question, which is answered here: http://bitcoin.stackexchange.com/questions/116/what-happens-to-my-bitcoins-if-lose-my-wallet-file-e-g-i-suffer-data-loss-and-m

Another reason is so that you know who paid you. If you give the same address to everyone, it's harder to know who sent you the Bitcoins.

But as far as I can tell, as soon as you create a transaction bundling the money from several addresses and sending them to one other, everyone can tell that these addresses belong together? Or am I wrong there?

@glglgl: That's true, but it does make it harder to trace your funds. Also, in the future we'll see increased popularity of all sorts of smart transactions and dedicated mixing transactions, so it's not guaranteed that two inputs in the same transaction belong to the same person.

@glglgl You might guess so, but there's no easy way to know what the meaning behind a transaction is. Say you see money from accounts A, B, and C move to D. You check back and you see A got money from AA, B from BB, and C from CC. Now, do A, B, and C belong to the same person and the transaction's a ruse? Or are they three people who just all paid the same person? The problem is, you can't tell ruse transactions from real transactions.

Another reason is extra security. Once you make a transaction you reveal your public key. Yes it's public and should be safe, but if a serious weakness is ever discovered in Secp256k1 then funds where the public key is known are at risk first.


text:
What is block forwarding logic of the Satoshi Client?
Could anyone explain in simple words what does the reference client do when it receives a orphan, stale or best-chain block regarding sending "inv", "block" and "getdata" commands?
An interaction diagram or concise description would be very useful.
The block forwarding logic is spread all over main.cpp source code.
A complete answer should allow to respond these simple questions with true/false:
a. An orphan block received from a peer is not announced to the remaining peers until the parents are found ("inv" command not sent immediately).
b. A stale block (not in the best chain) received from a peer is not announced to the remaining peers until it becomes part of the best chain ("inv" command not sent immediately).
c. Some blocks are forwarded even if they are not requested by peers ("block" command issued even if "getdata" not received). Which blocks?
d. Orphan blocks can be requested by peers using "getdata".
e. Stale blocks can be requested by peers using "getdata".
f. Nodes request whatever block it's announced by a peer "inv" command for which they don't have the hash, being stale, orphan or invalid.
This link https://bitcointalk.org/index.php?topic=41729.0 describes the interaction, but it's terribly complicated. Can it be described in more simple words?


text:
How does one mine Stellar
I was able to mine Ripple for a time using boinc, will Stellar offer something like this? are there other ways to mine Stellar?

There is no mining in either Stellar or Ripple. Both systems had all their currency units created at inception.
I am at a loss as to what you were doing when you were "mining Ripple"? Where you perhaps offering your computing power in exchange for being paid XRP?

Ripple and stellar dont have a mining mechanism. They verify transactions in decentralized servers and as far as I know you cant be a server. So Im not sure what you mean by minimg ripple and stellar.

Someone was paying you to run Boinc. Just like someone could pay you for goods and other services. It had nothing to do with mining. I'm sure there will be other opportunities in the future to buy Ripple or Stellar or to get paid with them.

The Stellar network does not have a mining-based currency. At the network's genesis, 100 billion stellars were created. The only other stellar creation mechanism is inflation. To account for both economic growth and lost stellars, there is a fixed 1% annual rate of new stellar creation. These new stellars will be generated on a weekly basis and distributed via a direct voting method.
Mining in the Bitcoin network:
1) creates the currency
2)distribute the currency
3) verifies transactions across a distributed, decentralized system.
Stellar achieves the first by generating the stellars at genesis. Distribution of stellars is regulated by the Stellar Development Foundation, the nonprofit that supports the protocol. 95% of all the stellars are set to be distributed to as many people worldwide as possible through a series of giveaways specified in their mandate. Stellar achieves the third—decentralized agreement—with the Ripple Consensus Algorithm.
In future, Stellar plans to switch to a new consensus algorithm called Stellar Consensus Protocol (SCP). The technical details of SCP are detailed in a white paper by Stanford Professor David Mazieres.
One can acquire stellars by trading on an exchange, trading within the Stellar network, being a recipient of inflation voting, and/or through the Foundation's giveaway programs.

"Distribution of stellars is regulated by the Stellar Development Foundation,". How do I distribute the lumens (formerly, stellars) if I am a private blockchain leveraging Stellar?

"All these Stellar Cores—the network of nodes—eventually agree on sets of transactions. Each transaction on the network costs a small fee: 100 stroops (0.00001 XLM). This fee helps prevent bad actors from spamming the network."

https://www.stellar.org/developers/guides/get-started/index.html

They collect transaction fee's and offer their core to download.. Sounds like mining fees to me. However they never mention "mining"
So to mine install the "core" software I guess. Trading for XLM or being gifted XLM is not the same.

running the core software does not mean you will receive rewards based on transaction fees like bitcoin miners do. See the FAQ: "The network also collects a base fee for each operation in a transaction. The funds from base fees are added to the inflation pool. As a balancing measure for the ecosystem, anyone who holds lumens can vote on where the funds in this pool go. Each week, the protocol distributes these lumens to any account that gets over .05% of the votes from other accounts on the network."


text:
How vulnerable is bitcoin to quantum algorithms?
Assuming that quantum computers are implemented some time in the near-ish future, how vulnerable is Bitcoin to decryption via quantum algorithms? For example, Shor's algorithm enables a quantum computer to prime factorize in polynomial time. A variant of it can crack ECDSA.
However, Bitcoin relies on a scripting system, so if quantum computers are created, one probably can just switch to a secure script1
Is Bitcoin vulnerable to attacks from quantum computers? Are these vulnerabilities fixable2?
1.  Then again, there are limits to scripting and quantum computing may make it impossible for any script to work.
2. "Fixable" can both be client-side fixable, where everyone just tweaks the script they use and transfers all their money to a clean set of addresses (thus securing all their bitcoins with the new script), or protocol-side fixable, where the protocol is tweaked and everyone downloads a new client. The latter is nor preferable, since the old bitcoins will probably be lost in the process.

relevant (foud out about it after I posted the question): http://pqcrypto.org/

Related: http://bitcoin.stackexchange.com/questions/6062/what-effects-would-a-scalable-quantum-computer-have-on-bitcoin

In short, yes, Bitcoin would be vulnerable to some variation of Shor's algorithm and quantum computing, as would basically every kind of crypto we use today. While ECDSA uses the elliptic curve discrete logarithm problem for its security, rather than the prime number factorization problem, you are correct in stating that a variant of Shor's can be used to solve the ECDLP in similar time. I believe there are similar threats with regard to SHA256, which is heavily used in Bitcoin's mining process.
You are also correct in stating that Bitcoin relies on a scripting system and is itself an open-source distributed computing project. Assuming you can arrive at a network consensus it is absolutely possible to change basically any aspect of Bitcoin - you just have to get the whole rest of the network to agree with you. I don't imagine that would be an issue if ECDSA or SHA256 were broken.
It's also entirely possible that the whole project itself could be forked to create an alternate version of Bitcoin similar to others which already exist. There is a variant called Litecoin, for example, which uses scrypt instead of SHA256 for mining - implementing an alternative to ECDSA could be easily done in a similar manner.
This, perhaps, is the true brilliance of Bitcoin: it's a Pandora's box that cannot be un-opened. Bitcoin as it exists today may or may not exist in a decade. Perhaps there is some unforeseen flaw that will soon be discovered, but that flaw will be fixed and the idea will live on. Assuming that there is any reasonable encryption/signing algorithm that is safe from quantum computing, it will be adopted and the cryptocurrency world will move on.

If ECDSA was broken, would the fix involve just telling everyone to use a better script? Or does a better script not exist? (after all, the addresses depend on ECDSA as well)

Yes and no. "telling everyone" implies that there is a central authority where there is none. That said, if the devs came out and said "crap guys, ECDSA is broken, here's a new version with a different algorithm, please please install it" I think most people would tend to listen.

Realistically, I think such a break would more likely result in the migration from one blockchain to another. If SHA256 were broken, for example, I would foresee a migration to Litecoin before I would guess at a modification to Bitcoin. This is the one and only redeeming virtue I see in the altcoins, though that's just personal opinion. You're welcome to prefer what you like, I'm just happy cryptocurrency doesn't exist as a monoculture any more.

Ah. So the protocol is quantum-proof, just that the standard protocol (the in-built script that all clients use) is not.

Basically, yeah. The protocol is just a script that communicates signatures and hashes - what algo you choose to do the signing and hashing can be swapped out lego-style.

Hmm. Wouldn't all scripts be ECDSA dependent, though? The bitcoin addresses (public/private key pairs) are ECDSA. Or is it possible to abandon ECDSA and talk about a new set of  key pairs just by changing the script? (Basically, are there any references to the btc address outside of a script block?)

Crypto currencies such as bitcoin will always be a step ahead.
Post-quantum Cryptography is already being researched to combat quantum computers before they have even evolved enough to be considered a threat.


text:
Where can I download the Litecoin binary for OSX?
Where can I find a compiled litecoin minerd binary for Mac OS X?
Perhaps a multi-coin implementation?

So Litecoin or multi-coin?

Asked it in the forums, and here's the response:
https://bitcointalk.org/index.php?PHPSESSID=039d3d0433adcf037196613c03d139e1&topic=47417.msg605132#msg605132
Edit - direct link to github downloads

Actually, it's easy to find from litecoin.org

Is it worth taking the data from there and posting it here for edification?

@DominicTancredi - added a direct link to github.

Here,
as mentioned in litecoin.org

Today you would be using a mining application like minerd:
https://github.com/downloads/metonymous/cpuminer/minerd

In case you didn't notice, you are replying to an answer that is almost exactly two years old. Back then the standard wallet also had mining capabilities. Link only answers are generally frowned upon, could you please elaborate on what your link leads to?


text:
One dataset for many wallets... how?
It takes a while to download and process the transaction log.
Doing that for dozens of wallets would be a big waste.
I want to run just one client full time as a log processor.
Then for each wallet, symlink the log processor's data
files into each wallet's homedir.
Even if I can't tell each client to NOT pull down new
logs and process them, I can still copy the processor's ones
in as needed and then start the client.
So what files in the homedir are wallet specific, wallet signed,
or in ANY way linked to your wallet and keys/ids, etc?
And what files are completely safe/anonymous to redistribute, crossplant,
etc.
How do I separate the identity files from the network data files?
What files are, and do, exactly what?
Thanks :)

Only the wallet.dat file is specific to the wallet. You can stop the client, swap out the wallet.dat file for a different wallet, and then launch the client again. You may need to start the client with the -rescan option -- the client will do the right thing automatically in most cases, but there are a few corner cases it mishandles without -rescan.


text:
Litecoin mining 10 times slower than a couple of days ago
I have a 5850, and have been mining with it for about a week.
With GuiMiner I can mine bitcoins at about 275Mhash/s.  This has not changed.
A couple of days ago I setup Litecoin mining and it was working at about 350Khash/s, which at the time was about the same profit as Bitcoin.
But now when I mine litecoins I'm only getting 35 khash/s.
I'm getting the same speed with CGMiner or Reaper.  I just started the exact same setup I had last week and I'm getting the crappy result.  I've been messing with settings and config, but no change.
I have rebooted, no change.  I can change back to Bitcoins anytime and get 275Mhash/s with CGMiner, but when I change CGMiner to Scrypt mining it drops to 10% what it should be getting.
I can't think of anything that would cause this.  Any thoughts?
Scrypt CGMiner mining:
http://puu.sh/2d7Mp
Bitcoin CGMiner mining:
http://puu.sh/2d7NW
Current CGminer command:
cgminer --scrypt -o x -u Liquid5n0w.1 -p x --intensity 12 --worksize 256 -g 1 --lookup-gap 2 --thread-concurrency 7200  --fix-protocol

please please let me know if you can find any answer to your problem. I'd pm you if I could. I've scoured the web looking for an answer for this, I have the exact same problem as you.

I have found the cause:
I had GUIMiner to start on startup, and even though I was stopping it before I'd try to use CGMiner or Reaper, it did something to the drivers and would prevent LTC mining from starting correctly.
If you have a similar problem to this, try to disable GUIMiner on startup.

Try what I sent to you with the modded version of cgminer and see how you get on with that. If you are mining with .conf file grab the default one from cgminer and relapse it and use and create .bat files if you know how to do that and progress from their.
Other than that try removing all drivers and starting fresh. If that does not work with custom modded cgminer then you could of done something to the card, could be anything. the other option you have is to try the card on another system.

"Try what I sent to you" Could you post what you sent him publicly, so that others can benefit from this answer a year or two down the line?

This has happened to me several times, and I have always been able to resolve this by deleting the .conf file (for cgminer this is /cgminer.conf)
Since you have already been mining at a nice rate, I do not think this is an issue with the command you are passing, however others with similar problems might want to try the following tutorial:
https://bitcointalk.org/index.php?topic=97143.msg1069730#msg1069730
Hope this helps!

I can't seem to find cgminer.conf  The only one I have is example.conf


text:
Is it possible to figure out whether two addresses are in the same wallet?
I'm wondering, if I sent some bitcoins from one of my own addresses to another address in my wallet, will it be possible for someone to figure out that both addresses are in the same wallet? Or can I claim the other address is not my own and no one can find out?

possible duplicate of How anonymous are Bitcoin transactions?

I noticed that there is nothing on that page about figuring out that certain addresses are in the same wallet, despite the fact that there has been specific research on that topic.  Perhaps this question could be rephrased to more specifically address that topic?  Or if we want it all to go on that other one, maybe someone (KoKo or anyone else) could start a bounty on that question for an answer detailing this point.  Personally I favour rephrasing this question since it is an important topic and really much more specific than "how anonymous are transactions".  Any feedback on this KoKo?

It is possible to tell that two addresses are in the same wallet if they both appear as an input of a transaction. This indicates that one person owns both of them as they can spend both of them.
It is also quite likely that when you are sending a transaction that has one neat input (say, 1BTC), and one not so neat (say, 0.59721364BTC), that the latter is most likely a change left over from a transaction you sent to someone and is being sent to another address you own from the same wallet. This claim could be possibly deniable, but should be true in most cases.

Re first paragraph: Having both addresses as inputs of a transaction is evidence, but not definite proof, that they are owned by the same person. There are many use cases when different people may want to each supply an input.

@MeniRosenfeld Well, I personally can't think of many. Same thing could be achieved by multisig addresses and just sending the person the money from a transaction you want to spend together.

No. Once you send to the multisig address you're at the mercy of the other party. The whole point with multi-input is to make atomic swaps where neither party can deny the other - e.g., mixing transactions and swapping colored coins.

@MeniRosenfeld They could use 2-out-of-2 multisig address. But I get your point.

I'm not sure you do. To use a 2-of-2 multisig address they'd first need to send to this address. Once coins are in the multisig address, if the other party loses their key, you lose the coins. The other party can also extort you taking the coins hostage.

Shouldn't it be "neat output" instead of "neat input"?

No, it is not possible to determine definitively if two addresses are in the same wallet. The protocol does not have the concept of the wallet. The wallet is a concept within the client.
That is to say, that the client presents the concept of a wallet as a collection of addresses. The only relation between addresses that the protocol knows about is senders and receivers, or, really, inputs and outputs.
It may be possible through a thorough analysis of taint to determine within a reasonable amount of certainty that several addresses are related to each other in a wallet.

There is no way to prove in the protocol that two address belong in the same wallet when you send from address A to address B in your wallet. Of course, if you are using some kind of online wallet they do know, but I'm assuming you are using a full one.
However, there can be clues that combined can be quite definitive.
1. Clues when you send the transaction
However, depending on the amount in address A, sending all funds to B with no change could be a clue that both belong to the same person. This is not a problem if you are sending a round amount like 1 BTC, but if you are sending 0.82421871 BTC and there is no change it is weird unless you are sending all your funds to donate or pay for something without a fixed price. It is the same if you send from A a round amount to another address and B gets a very weird amount.
2. Clues after the original transaction

Spending from both addresses in the same transaction. This is no proof because there are ways to build a transaction with inputs from two wallets, but it is extremely rare.
Sending funds between the two addresses frequently, specially if you do it both ways (from A to B and from B to A). This could happen with two parties that work a lot together, but it is a clue of some relation.
Sending from both addresses at the same time, even if it is to different addresses (you send two transactions, one from A and another from B, that get to the same block long after you did the original one). It can be a coincidence, but it is one more signal.

3. IP address clue
This is extremely unlikely, but if you connect to a rogue node that records your IP address when you send from A to B and then you connect to that same rogue node (or another one acting in coordination) when you send from B to somewhere else, it would have the same IP address associated to both addresses. You could avoid this by using Tor or changing your IP address in some other way.

It depends.  Bitcoin is traceable but pseudonymous.
So there would be a path from your first address to your second address.  There's no way to prove that the second address is in your wallet at that point.  But when you spend from that second address, any party that knows the second address is yours would know that the second address came from funds from the first address.
In other words, simply moving funds from one address to another address is not an effective measure for protecting your privacy regarding your financial transactions.

If you had the xpub you could see all the addresses derived from a particular seed, and as such determine if two addresses are linked in the manner you described. However it's extremely rare that any entity other than the actual wallet (in some cases) would be able to see this "extended public key" as it is very much a bit of private data.

Each address (corresponding to a public key) in your wallet has a corresponding private key. All private keys in the wallet are generated based on a single seed / passphrase. This why you are able to reconstitute your wallet on a new clean device. So a "wallet" is not strictly a client-side concept. Anyone with the phassphrase + pwd basically has access to all your private keys. Since nobody except the owners know about the passphrase there is no way for someone to mathematically prove that two addresses came out of the same wallet.
However, like others have mentioned, I/O and UTXO can provide some clues about the association between two addresses.

an public key is an public key and an address is an address

@Mercedes they are essentially the same thing where the address is a short and convenient version of the public key. simply address = RIPEMD160 (SHA256(PK))

If you compare two addresses, it is impossible to determine if they were derived from the same public key.


text:
Miners, did Catalyst version 11.9 fix CPU usage issue for you?
Miners, did the new Catalyst version 11.9 fix 100% CPU usage issue for you? what's the best version of Catalyst to use for mining?

For one of my computers, yes - it also fixed my inability to watch youtube videos while mining on one computer but not the other.

Catalyst 11.9 resolved the issue for those mining on single GPUs but not multiple GPUs (including single cards which contain multiple GPUs like the 6990 and 5970). You can try setting the -f flag to higher numbers until CPU usage is reduced or try setting -aggression to 10 or lower. Note that these settings might reduce your hashrate significantly depending on how aggressively you change them from defaults.
The bug in question was introduced in Catalyst version 11.5 and at the time affected only multi-GPU setups. It remained in place for version 11.6 and in 11.7 actually began affecting single-GPU systems as well. In 11.9 the single-GPU bug was fixed, but the multi-GPU bug is still in place. There is a beta release of 11.10 available but I've not heard anything about whether it fixes the 100% bug or not.
A quick search shows that the 11.4 drivers are still available for 32 and 64 bit systems. Assuming you don't need anything that the newer drivers offer for non-mining purposes, 11.4 is probably your best bet. If you're running dedicated rigs it's definitely your best bet.
Edit: It appears that 11.10 did not fix the multi-GPU bug so 11.4 is still your best bet.

11.10 does not solve multi GPU 100% bug.  It may not be fixed in time for 11.11 either.
Miners should express to AMD their desire to see this bug finally fixed.
http://forums.amd.com/devforum/messageview.cfm?catid=390&threadid=153211

Thanks for the info, I'll add it to my answer for completeness

I still get 100% cpu when with Catalyst 11.9 when I use the -f1 flag on poclbm. I fixed it by bumping up to -f4, which gives me a slightly higher hash rate than the -f6 I had to use previously to fix cpu usage.

A better solution would be to downgrade drivers and not lose hashrate by toying with -f and -aggression settings


text:
Can quantum computing improve Bitcoin mining?
Would a D-Wave 2 with 512 qbits be faster than the fastest ASIC when mining bitcoins?

There are two different things here:

D-Wave machines ARE ASICs. They only solve certain particular problems. It is not really clear they take advantage of quantum effects or that they perform better than a classical ASIC working on the same problem would. In any case, they would be quantum ASICs, not general purpose quantum computers.
Mining can be improved using Grover's algorithm (http://en.wikipedia.org/wiki/Grover%27s_algorithm). When you mine, you basically have a black box that you feed with guesses and the box answers whether you have "won" the block or not. The number of possible answers is your difficulty. It is easy to produce by chance an even number, not so easy to produce a multiple of 5743.

Imagine you have a quantum computer and a classical computer each with a black box which takes the same time to check your guess. Each guess has a probability of being right equal to (#right answers)/(#total possible answers).
In a classical computer you just try one by one. On average you need about (#total possible answers)/(#right answers) tries to hit a block. In a quantum computer or a quantum ASIC implementing Grover's algorithm, you only need to use the black box (what they call the "oracle") the square root of (#right answers)/(#total possible answers) times. There are some other factors, but roughly you get a quadratic advantage.
Of course you never get this kind of fair comparison. I wouldn't really worry about quantum mining for a long time. Even if it were faster, it would probably be much more expensive. Think that you can always mine faster with more expensive equipment. You could mine faster with a supercomputer, but, at the cost they come, you better use it for something else.

Suppose it takes 1 tera tries to find a correct answer. Accordingly with your answer it only takes 1 mega tries to do it with a quantum computer. So if a quantum computer is a million times more expensive than a normal ASIC it still worth mining in it.

You are right, but that's assuming it takes the same time/cost to try each answer. Hashing is quite efficient in classical computers. The quantum oracle is a bit more complicated. Hashing is irreversible and you need a modified reversible version which preserves the input. For SHA256 that takes about 512 qubits. With such a quantum computer you could do things like quantum simulation or factoring which have a better speedup. You could try, but you need a hashing efficiency comparable to classical computers. If quantum hashing takes 10000 times longer the advantage is not so impressive.

Wouldn't you need at least enough qubits to represent a whole minimal block candidate i.e. at least block header and coinbase transaction?


text:
How much would cost to mine a block with Google Compute Engine?
Google has opened its Compute Engine and it has a price list. How much would cost to mine a bitcoin block with Google Compute Engine?

I'm not going to crunch the numbers right now, but it wouldn't be worth it.  It would most likely take more than a year.

It's CPU only - I doubt it would be profitable.

They tell it's good to render videos. I wonder if a GPU farm wouldn't be much more cost efficient for that purpose too.

Even if it was a GPGPU cluster, you will not make a profit from the prices they are charging. Mining at this point is only profitable with FPGA, ASICs and certain GPUs pending power consumption.

That's not what he asked.

@StevenRoose because the question suffered from the xy problem. He likely should have asked "is it profitable to mine with Google Compute Engine?".

@StevenRoose He asked a question that has a vacuous answer. I suspect his concern is what Lohoris pointed out. Is it profitable. I can pass the Turing test and infer meaning :)


text:
Can the price of Bitcoin ever be stable to the USD?
It seems like the only way to sell BTC for products/services is to have the BTC reflect how other currencies are doing. I'm not great in economics but can it ever be stable?

This smells like speculation to me. Are there fortune tellers among us?

No, it won't; and by definition: it can't. Hope that was helpful ;)

This question does not have only one correct answer, it is subjective/argumentative: In order to be constructive and informative, give long answers rather than short. Focus on explaining "Why?" and "How?". Back up any opinions with facts and references. Opinions by themselves are noise and will be deleted.

As the public develops more confidence in the currency and as the currency is used in wider volume (people start buying more and more things with the currency and it starts to change hands a lot) it will start to stabilize.
The current instability seems to be driven by speculation. A lot of people are not using bitcoin as a currency right now but just as some investment to gamble on. Hopefully that view of bitcoin will change, soon.
Not sure why you would want to compare BTC to the USD, though... since the USD is not that stable recently, but that is nitpicking and not addressing the spirit of the question.

No currencies are stable unless they have a central bank making it artificially stabile. When that is said, the stability will largely be depending on the size of the economy. I do not, however know exactly how to measure the size of the Bitcoin economy, but I assume it should be measured in terms of the total amount sent between people or companies over a period of time (which would be similar to the measurement of GDP).

If we want something like GDP to measure, the blockchain IS an open book :) There's even a ticker for BTC sent in the last 24 hours on http://bitcoinwatch.com/

The price is a reflection of basic market forces at work: supply and demand.  Currently relatively small transactions represent a large portion of the market, so this can naturally lead to some inefficiencies.  Nobody can know for sure whether stability will be reached, but it seems likely to me that stability will tend to increase with the number of active users.

the instability is not a reflection of supply and demand... it is a reflection of speculation.

@Artem in the case of bitcoin, wouldn't it be speculation about future demand?

@Mocky I guess it depends how broadly you want to think of demand... but in general speculators speculate on all kind of crazy things. Sometimes the prices of small currencies skyrockets randomly (obviously it means someone demands to buy the currency or a major holder refuses to sell - cutting supply - but it doesn't mean that there are suddenly more places where the currency is used, for instance).

Bitcoin is still very new, it is unlikely that it will sit at one price for a very long period of time.  When all of the bitcoins have been mined it is much more likely to sit at a stable price.

why would having all the bitcoins minted stabilize the currency? Are you suggesting that the current fluctuation is due to inflation (which is what mining does)? Only if you ascribe the fluctuations to inflation does mining have an effect. It is not inflation that drives the variability in the price right now...


text:
I want my website to accept bitcoins without dealing with security issues
I want my site to accept bitcoins (and automatically reward users with it), but do not want to deal with the security issues that would entail.
Is there a SaaS (Software as a Service) which could handle all the hassle for me?

I would suggest integrating https://bitpay.com/
They charge you like any other service but they do all the payment stuff. Also they have plugins for most open source shopping carts Bitpay plugins
Also keep you wallet offline to avoid problems.

I want to automatically reward users for doing certain actions, so I guess keeping wallet offline is not going to work. The second question is how much can I trust bitpay?

You can trust them in a way you trust any other payment gateway...How do you know that paypal will not disappear tomorrow with you funds? Bitpay is the largest bitcoin payments gateway read this article
Keeping wallet online is very insecure, I would at least keep it away from the server and only connect to central database to get list of transaction to send.

@Moonwalker - Wordpress and Mega both use Bitpay to accept bitcoin payment.  I think Namecheap does also.

Coinapult has an API that you can use to send coins to a user's mobile SMS/text number or via e-mail.
It's not really the right way to do it but it is one way of doing it.
You could also do it by distributing an Instawallet URL.   The person that knows the Instawallet URL can spend the funds.
Redeemable codes would be another method.  You can hand out Mt. Gox redeemable codes denominated in BTCs.  The user needs to create a Mt. Gox account to redeem the voucher though.
You could also distribute a private key like what is done for Paper bitcoin wallets.  The methods for redeeming those are not user friendly though.


text:
Is there bitcoin implementation in python or C#?
I want to play with the implementation to better understand the inner workings of Bitcoin. I'm familiar mostly with python and C# and found no clients in either of the languages. My C skills are rusty because I haven't done any C in last decade.

C and C# are completely different.

@ppumkin: Yes, that's his point. He wants a C# implementation because his C is rusty.

Yes - My point was that is going to be difficult as C is based on 8086 compiler and C# on .NET Libraries. There will be a lot of headaches, especially cryptographic, which BTC is based off.

There isn't yet a complete implementation AFAIK, but there are different libraries that implement bitcoin features (wallets, keys, utilities,
Depends on whether you want an implementation of bitcoin network protocol or wallet or just an overlay on top of the JSON-RPC interface of bitcoind.
Useful code on github:
https://github.com/jgarzik/python-bitcoinrpc - Python interface to bitcoin's JSON-RPC API
https://github.com/etotheipi/BitcoinArmory - Python-Based Bitcoin Software
https://github.com/gavinandresen/bitcointools - Python-based tools for the Bitcoin cryptocurrency system
https://github.com/jgarzik/python-bitcoinlib - Bitcoin library
https://github.com/spesmilo/electrum - Electrum thin-client
https://github.com/spesmilo/electrum-server - Electrum server
https://github.com/spesmilo/sx - Python CLI tools

NBitcoin is the most complete lib to date, here are links and articles about it.
NBitcoin Github : https://github.com/NicolasDorier/NBitcoin
NBitcoin Nuget : https://www.nuget.org/packages/NBitcoin/
Intro : http://www.codeproject.com/Articles/768412/NBitcoin-The-most-complete-Bitcoin-port-Part-Crypt
Stealth Payment, and BIP38 : http://www.codeproject.com/Articles/775226/NBitcoin-Cryptography-Part
How to build transaction : http://www.codeproject.com/Articles/835098/NBitcoin-Build-Them-All
Using the NBitcoin Indexer : http://www.codeproject.com/Articles/819567/NBitcoin-Indexer-A-scalable-and-fault-tolerant-blo
How to Scan the blockchain : http://www.codeproject.com/Articles/784519/NBitcoin-How-to-scan-the-Blockchain (You can dismissthe ScanState for that, now I concentrate on the indexer)

In addition to aantonop's links, there is also for python:
PyCoin https://github.com/richardkiss/pycoin  Utilities for transactions signing and verification, and creation of deterministic wallets according to the BIP0032 standard.
PyWallet https://github.com/jackjack-jj/pywallet bitcoin wallet importer/exporter


text:
Is pruning transaction history implemented in Satoshi's bitcoin client?
The original bitcoin paper suggests a method to discard old transactions. One should compute the Merkle Tree of the entire transaction history, and store only part of the tree.
However, I didn't notice this method implemented. BuildMerkleTree stores it in memory only, and seems to assume you're holding all transaction history, and the serialization method stores the actual transactions and does not store the Merkle Tree.
Is that implemented? Can you give me a reference to where is it in the code?
If not, is it planned for a specific future release?

bitcoin.org is where the standard client is hosted, but it's not generally used to refer to the client itself - it's usually called the standard client or the Satoshi client. AFAIK it does not currently implement pruning transactions.

@MeniRosenfeld Fixed, thanks. I'm not sure how exactly it should be done, and an implementation can make things clearer. Any calculation for how big a block will be with no pruning, in the next few years?

I edited your question to include asking when is such a feature planned, hope you don't mind. (Also added a closing question mark to the title)

I was sure I had asked a similar question (about planning) in the past, but didn't find it now. I vaguely remmeber Gavin saying that "it's the next thing on the roadmap after multisig", but I don't have a citation, and I think it wasn't formalized anyway. For the cord, the straight answer to your question is "No, the current client does not prune history".

possible duplicate of Is "Reclaiming Disk Space" already implemented? How effective will it be?

See also the discussion and links in https://en.bitcoin.it/wiki/Thin_Client_Security

Since Bitcoin Core v0.8.0, the validation database ("chainstate" or "UTXO set", or "account balance sheet") is separated from the blockchain. When a new block comes in, its effects (removing spent inputs, and adding outputs) are applied to the database. This means blocks are still downloaded and verified like before, but they aren't used for validation anymore afterwards. Blocks are still stored on disk in order to send them to other nodes that are synchronizing, or to rescan for old transactions.
Since Bitcoin Core v0.11.0, it is also possible to run in a true pruned mode, where the blocks on disk are actually deleted after a while. Since v0.12 it is possible to use the wallet while running in pruning mode. Since v0.14 it is possible to manually prune (by issuing an RPC command rather than have the application decide).
Note that neither of these mechanisms rely on the mechanism described in the Bitcoin whitepaper.

Related: https://bitcoin.stackexchange.com/questions/37496/how-can-i-run-bitcoind-in-pruning-mode

I would assume this is not implemented because of the problem that Pieter mentioned. Having a client that only stores a pruned version of the block chain can't be friendly to other clients that don't have this pruning feature implemented since it won't be able to retrieve the original block chain.
Since a variety of clients are still undergoing development allowing alternative clients the choice of how to handle their block chain data allows for new innovations. For instance, it allows analysis of how Bitcoin has behaved over time. Even if you have not recorded this from the start.

Here are two options.
The first can be blockchain pool which will be torrent like storage and can be implemented independently in wallets (today's 30GB spread to 2000 clients with 50% redundancy will cause only 30MB size)
Second could be some kind of defragmentation, where is needed development of protocol. Here will be no problem to add block on the top of blockchain which includes let say 100k oldest blocks as a copy, without zero balance accounts. Question is only if here will be significant rate of defragmentation.
assumptions

we do not need transactions which creates empty accounts (all was sent)
we do not need transactions which do not change balance  (all was sent back)
we can set some time limit to dead accounts (only one transaction topped ou account and account never been used)

It is not simple solution and inactive account can not be refreshed until they are not running, then the last item is not quite safe.

No, it requires the entire history to verify new transactions (due to how the security of a new block in the chain requires the security of all previous blocks).
Some future client may not require the whole chain and not fully verify transactions, however I would not consider these secure for large transactions because I have no clue if the "skinny client" I'm on is not stuck on a malicious fork in the chain designed to allow double spends and someone has not ran off to Mexico with my Bitcoins.

This is not correct. You do not need the entire history to verify transactions - spent and well-buried transactions could safely be removed if it were implemented. With the current network protocol, such a pruned node is not able to provide the block chain to other full nodes, however.


text:
Do miners have to start over whenever a block is found?
If I understand correctly, each miner selects a set of pending transactions, puts them in a block, and then tries to sign that block. Pooled miners do the same, but the specific set of transactions is selected by the pool server.
Since each block must link to the previous one, does it mean that whenever a new block is found (by another miner) the whole process must start over?

Which approach are you describing, Solo mining?  Pooled mining (and if so, one that uses getwork, or getblocktemplate?)

Interested in answers regarding all types of mining methods

In a sense, yes.
However as the mining process is essentially guessing the right number from a very large set of possibilities it's misleading to say you start the process again as you're just as likely to guess the next block first try as you are to have guessed the previous block. You basically start the process each "guess" anyway, whether you try again on the same block or start trying a new one is of little consequence.
You could very well find a new block the very second after you accept a block. In that case, you wouldn't have found a block if you had kept mining on the old block.


text:
Mining with low specs?
If I have a computer with low specifications (2GB RAM, 2.13 GHz, integrated graphics), is there any way to mine normally with Bitcoin-qt? If not, will joining a pool with these specs be worth the time and effort? What kind of specs are normally recommended for mining?

It would almost certainly be not cost-effective, i.e. the electricity costs would be more than the bitcoins produced, and even if electricity was free, the general computer wear could balance out the few cents earned.

No, this would not be worth it. CPU mining is extremely slow and there is probably no OpenCL driver for your integrated graphics. You could however hook up FPGAs to that computer, or in the future, bitcoin ASICs.
Currently recommended hardware would be FPGAs and/or fast AMD graphics cards.
In the near future there are several ASIC-based mining devices scheduled for launch. These will drive up the difficulty, making today's FPGAs and AMD GPUs seem slow.

Mining is generally not about the CPU, but the GPU. You ought to check what graphic card you have in your computer, reference the Mining Hardware Comparison on the Bitcoin Wiki, and then do some calculations on such sites, like my Bitcoin Calculator for example. If you think your setup will provide you with enough bitcoins for your buck, go for it.
However, as there are a lot of new miners introduced to the Bitcoin Network that use power-efficient FPGAs or ASICs, even the most efficient GPU miners might struggle to compete.
You might also look into some alternative Bitcoin-like currencies that are "GPU-resistant", that is, they are most efficiently mined with CPUs. They might be more efficient for your setup.


text:
Accounting for currency destroyed in lost wallets?
Bitcoin will eventually be capped at 21,000,000 Bitcoins, but what happens to all the wallets that are lost? I'm sure thousands of BTC are already as good as destroyed. Even if there weren't millions of USD being printed consistently, they would still print not only new money to replace the old, but also to account for destroyed bills. Would replenishing the supply of lost currency be possible in Bitcoin?

Also related, answering the other part of the question: http://bitcoin.stackexchange.com/q/484/516

could the block chain be used to reimburse people with lost wallets? could a future version of the block chain do this?

Bitcoins can be divided up infinitely. So if there was just one bitcoin left (the rest are lost) then there can still be a viable economy with fractions of bitoins.
Lost wallets are only a problem for the people who lost them, not for bitcoin. It would of course limit supply and push the the cost of bitcoins versus other currencies.

Each bitcoin can only be divided into 100,000,000 units. I suppose we could survive on one coin, but it's not infinitely divisible.

@tkbx: It can be divided into 100,000,000 units today. That would change long before it became a problem.

@DavidSchwartz if they wanted to change that, couldn't they just change it so every bitcoin becomes 10?

@tkbx: Yes, that would certainly be one way to do it.

@DavidSchwartz so if they were to do either of those, would the people who maintain it just have to release a client update with the change?

@tkbx: It would be a bit complex. It would have to be planned well in advance, a consensus reached, software developed and tested, and so on. Then a block index would have to be chosen for the changeover. Software would be deployed that switched behavior once the chosen block index was reached. Anybody who hadn't upgraded before the changeover would be unable to understand the current blockchain.

@DavidSchwartz so basically it's like the weakness where a large mining pool can change the way the network works, but not maliciously?

@tkbx: Yeah, exactly. Power can also be used for good.


text:
Demographics on Bitcoin users?
Speaking with a large group about Bitcoins lately, I noticed that most people there came to like Bitcoins for different reasons. The shady ppl wanted drugs, the accountants wanted to avoid taxes, the Ron Paul people wanted more personal liberty and to end the Fed, The traders wanted new Forex opportunities, and the computer techies were in love with the elegance of the system...
So I'm really starting to wonder here, What are the demographics of the Bitcoin users? Has anyone attempted to do a serious attempt at finding those? Perhaps even a big website poll?
Inquiring minds want to know.

direct analysis of the blockchain:
http://getaddr.bitnodes.io/

I can't think of any known data about real demographics.
But here are some things you can consider to get an idea:

BitcoinCharts' currency distribution: Gives you a view on what currencies are traded the most, most currencies are country- or region-specific so this can be a measure.
BlockChain.info's real-time transaction mapping: You can literally see every new transmitted transaction appear on the map. (This is possible because all transactions are public and have an IP bound to them. But note that some users might use Bitcoin with tools like Tor so their location can be wrong.)

There's no IP address bound to a transaction.  BlockChain.info just reports the IP of the first peer that relayed each transaction to them, and since they connect to a lot of peers, it's more likely that's the IP of the originating peer.  But if I don't accept connections from BlockChain.info and don't connect to them myself, they'll never see my IP on my transactions.

A recent survey solicited to BitcoinTalk forum members:

http://bitcointalk.org/index.php?topic=88927.0

There was a Bitcoin survey recently: https://bitcointalk.org/index.php?topic=88927.0.


text:
USB hub busy when mining Peercoin with Red Fury ASIC running Minepeon
I have a RasPI running minepeon 0.2.5, a DLINK USB Hub and a Red Fury USB ASIC Bitcoin Miner 2.2-2.7GH/Sec By BITFURY
I've added my pool https://ppcoin.d7.lt/ and things looked good except nothing is mining.
The miner states it's running but the device id is 0 and hashrate is 0.
I've tried to start the miner manually in accordance to https://ppcoin.d7.lt/getting-started
cgminer -o stratum+tcp://stratum.d7.lt:3333 -u miner.1 -p 99999

It starts up but states that the USB hub is busy, I see it testing the Red Fury but after that it still is not mining.
Am I missing something?
Related Posts:

http://www.peercointalk.org/index.php?topic=499.msg17709#msg17709
https://bitcointalk.org/index.php?topic=251675.msg4841184#msg4841184

This issue helped me solve my issue:

https://github.com/MineForeman/minepeon-base/issues/13#issuecomment-33760864

running the command
sudo lsusb -v

I get this out put, is this correct?
idVendor 0x03eb Atmel Corp.
idProduct 0x204b LUFA USB to Serial Adapter Project
bcdDevice 0.00
iManufacturer 1 BFMG
iProduct 2 Bitfury BF1

add the lines below to this file
/etc/udev/rules.d/01-miner.rules

add these lines
# BF1
ATTRS{idVendor}=="03eb", ATTRS{idProduct}=="204b", SUBSYSTEMS=="usb", ACTION=="add", MODE="0666", GROUP="minepeon"

rebooted the server and now I see my miner!


text:
How do I get the temperature of my USB Miner?
Is there an option I can pass when running the miner? ( CGMiner / BFGMiner )
How does one get the temperature of a USB Miner? ( In my case BitFury )

Have you considered using an external device such as an infrared thermometer?

@GregHewgill to my understanding this USB Miner has a temperature sensor already, I just wanted to know how to access it

If your device has a temp sensor it will show in the API output and in the Text User Interface that is default when running at the command line

I don't see it though, is there an option to pass to display this information?

if you don't see it your device probably doesn't have a temperature sensor - most usb stick miners do not


text:
Is there a command line Bitcoin CPU miner for Windows?
Is there a Bitcoin miner that I can run using the command line on Windows? I want a CPU miner, not a GPU miner.

You do understand that at this difficulty level, you will not recoup your power costs from bitcoin mining? This link provides an idea of what hash rates you'll get from CPU and GPU mining
https://en.bitcoin.it/wiki/Mining_hardware_comparison I wouldn't recommend it even if the power is free. It just isn't worth the wear and tear on your CPU.

bitcoin-cli -rpcconnect=127.0.0.1 generate 1

You can install the standard Bitcoin-QT client, navigate to
\Program Files (x86)\bitcoin\daemon\

and then run
bitcoind -gen=1

However this isn't recommended except on the Test network because it is next to impossible to generate any coins this way on the production network.

One of the best for both LiteCoins and BTC is
CGminer
It supports both Linux & Windows
Download from here
https://github.com/ycros/cgminer/downloads
You can get complete instructions from
https://bitcointalk.org/index.php?topic=28402.0
Or just check the readme including in the zip
It Supports FGPA GPU and GPU for BTC & GPU for LiteCoins..there is extensive tuning instructions as part of teh community so if you want to get the most bang for your $$ then this is the one :D

Does the litecoin cgminer use IRC?  Also do you know if cgminer works with Butterfly Labs FPGA for litecoin?  I thought lightcoin was made to resist FPGA/GPU optimizations

ckolivas has got it working for GPU with TacoTime (big Litecoinminer) using both it & reaper for GPU Litecoin mining with cgminer being the most stable i.e 9 days and no probs with cgminer...FGPA wont work as the code is specific for BTC ..my bad should have stated FGPA only for BTC..have edited answer to suit :D

It Uses/Supports IRC as far as I know

This client includes a command-line miner which supports CPU mining (and GPU, should you have one available).
But unless you're mining in a pool, you're not going to get any benefit from CPU mining. And even with a pool, you'll get very little.