On 10/24/2008 01:12 PM, Jack Lloyd wrote: > .... is a very different statement from saying that > lacking such an attacker, you can safely assume your 'pools of > entropy' (to quote the original question) are independent in the > information-theoretic sense.
The question, according to the original poster, is not whether it is "safe" to assume that one of the entropy sources can be trusted. Safe or not, the question explicitly assumed that one of the sources was trusted ... and asked what the consequences of that assumption would be. In particular, evidently the scenario was that we started with N high-entropy randomness generators, but N-1 of them have failed. One of them is still working, but we don't know which one. In that scenario, XOR is a good-enough combining function, and nothing else would be any better. If somebody wants to discuss a different scenario, please clarify what the new scenario is. Suggesting that the "trusted" source is correlated with one of the other sources is quite contrary to the requirements expressed in the original question. That is to say, if the source is not independent, it was never eligible to be a trusted entropy source. If you want to quantify this, write down the _joint_ probability distribution for all the sources, and calculate the entropy of that distribution in the usual way. 1) There is _one_ very precise meaning for "entropy" that is well-established and conventional across a wide range of fields ... everything from kitchen appliances to cosmology. http://www.av8n.com/physics/thermo-laws.htm#sec-relevance 2) Authors are allowed to define and redefine terms however they please ... _provided_ they define any nonstandard terms that they use. Anybody who takes a well-established standard term and uses it in a nonstandard way has a double-extra-special duty to explain what he's doing. I assume the original poster was using the term "entropy" in the conventional, precise sense ... and until I hear otherwise I will continue to do so. --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]