On Mar 22, 2006, at 2:05 PM, Perry E. Metzger wrote:

Victor Duchovni <[EMAIL PROTECTED]> writes:Actually calculating the entropy for real-world functions andgeneratorsmay be intractable...It is, in fact, generally intractable. 1) Kolmogorov-Chaitin entropy is just plain intractable -- finding the smallest possible Turing machine to generate a sequence is not computable. 2) Shannon entropy requires a precise knowledge of the probability of all symbols, and in any real world situation that, too, is impossible.

`I'm not a cryptographer nor a mathematician, so I stand duly`

`corrected/chastised ;-)`

`So, if you folks care to educate me, I have several questions related`

`to entropy and information security (apologies to any physicists):`

`* How do you measure entropy? I was under the (false) impression that`

`Shannon gave a formula that measured the entropy of a message (or`

`information stream).`

`* Can you measure the entropy of a random oracle? Or is that what`

`both Victor and Perry are saying is intractable?`

* Are there "units of entropy"? * What is the relationship between randomness and entropy?

`* (Apologies to the original poster) When the original poster`

`requested "passphrases with more than 160 bits of entropy", what was`

`he requesting?`

`* Does processing an 8 character password with a process similar to`

`PKCS#5 increase the entropy of the password?`

* Can you add or increase entropy? Thanks in advance, Aram Perez --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]