Hi,

As promised in my earlier thread, I studied some of the strategies that a miner could use to optimize his use of a cooperative mining pool. I have watched slush's pool over a few days and didn't notice any evidence of a massive use of these strategies, so I think they're relatively unknown by the common bitcoin miner. I also provide pointers to mining pool owners who see this as a problem and want to "fix" their pool.

The file is here: http://www.bitcoinservice.co.uk/files/100

Here is the table of contents:
1 - Introduction
2 - A brief overview of pools
  - the creation of bitcoins
  - sharing the work
  - all shares are not equal
3 - Strategies
  - One pool
     * average time to find a block
     * should I join now or wait for the next block ?
     * how long should I work on one block ?
  - Several pools
    * When should I switch pools ?
4 - Consequences for the mining pools
   - Is this the end of pools ?
   - Are some miners currently using these strategies ?
   - Fixing the mining pools
5 - Conclusion

Edit: I believe, for the sake of honesty, that I should note that the pools at no serious risk of being completely broken by those strategies. It's just a question of earning more with the same amount of work.

Edit: due to the rise in BTC exchange rate, I changed the price back to 1 BTC.

Hello everyone.

I'm a computer scientist with some knowledge in cryptography. I wrote a paper describing a way to implement steganography inside the Bitcoin network: that is, storing hidden messages inside the network, that would be available only to those who knew where (and how) to look.

I tried to write it in a simple language, so that it could be understood by anyone. The only part that's a little bit technical is the security analysis. I would be happy to receive comments and provide explanations if needed.

The paper can be downloaded here for 1 BTC
http://www.bitcoinservice.co.uk/files/86

There is no implementation, as it is only a proof of concept. An actual implementation would be relatively easy to build from the official client, and I might do it if there was some demand for it (and maybe a bounty ).

Here is the abstract from the paper:
    The Bitcoin peer-to-peer network creates a dis-
    tributed, anonymous virtual currency. We claim
    that this network can be used to store informa-
    tion in a secure way. We propose a very sim-
    ple steganographic scheme as a proof of concept.
    That scheme is related a difficult graph theory
    problem (finding a maximal clique of a graph)
    and as such, provides good guaranties if prop-
    erly implemented. We give pointers as to what
    a proper implementation would be, and the con-
    clude by giving some thought to the impact on
    the network that such a scheme would cause if
    it became widespread.