Been pondering this rather interesting 1998 paper by Prof. Ron Rivest (the 'R' in RSA) - "Chaffing and Winnowing: Confidentiality without Encryption". It bends the definition of encryption somewhat - but introduces a couple of (possibly) useful concepts.
Text Version: http://people.csail.mit.edu/rivest/Chaffing.txt
PDF Version: http://people.csail.mit.edu/rivest/pubs/Riv98a.pdf
In it, Rivest says:
"Novel techniques for confidentiality are interesting in part because of the current debate about cryptographic policy as to whether law enforcement should be given when authorized surreptitious access to the plaintext of encrypted messages."
He goes on to say:
"Winnowing does not employ encryption, and so does not have a 'decryption key.' Thus, the usual arguments in favor of 'key recovery' don't apply very well for winnowing. As usual, the policy debate about regulating technology ends up being obsoleted by technological innovations. Trying to regulate confidentiality by regulating encryption closes one door and leaves two open (steganography and winnowing)."
There is another summary on wikipedia: http://en.wikipedia.org/wiki/Chaffing_and_winnowing
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