Precise definition for cryptographic protocol? Is there some precise definition of cryptographic protocol?
I'm asking because I have tried a few good books and they don't seem to define it (Douglas Stinson, Wenbo Mao, Trappe/Washington). The lecture notes by Goldwasser and Bellare come close, but don't really define protocols (and leave key distribution out of the protocols chapter, for example).

I've seen people include key management in protocols and others keeping it out; the same for secret sharing and some other topics.

So, does that mean there no widely-accepted definition for cryptographic protocols?

Edit: I'm not sure I was clear enough when I originally posted the question -- I wanted to know what usually is considered a "protocol" in cryptography and what is not (and not how I'd go about defining some particular protocol)
There are several definitions of cryptographic protocols, each of which tries to capture some particular features of interest.

I start with Goldwasser, Micali, and Rackoff definition (1985): They first defined interactive Turing machines (ITM), based of which they defined (two-party) interactive protocols. An ITM is a special TM equipped with one read-only and one write-only communication tape. A pair of ITMs  constitutes an interactive protocol if the read-only communication tape of party A coincides with the write-only communication tape of party B, and vice versa. The power of parties and the adversary model is then defined accordingly (see the paper).

The multi-party case was later defined by Goldreich, Micali, and Wigderson (1987). They modeled a secure multi-party game in an elegant way, though the paper (as Goldreich states himself) leaves a lot of doors open. For a more concrete discussion see: http://www.wisdom.weizmann.ac.il/~oded/pp.html.

Finally, a much stronger model was proposed by Canetti (2001). In his paper, he defines a framework called Universal Composability (UC), based on which he defines the cryptographic protocols and puts forward a notion of security for them.

As far as I recall, the last paper cites a lot of other works which try to define and model security protocols. Therefore, I strongly advise you to take a look at it.