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 BTChttp://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.