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The following archive was created by hippie-mail 7.98617-22 on Fri Aug 21 1998 - 17:20:17 ADT
Carl Ellison (cme@clark.net)
Sun, 12 Jul 1998 14:12:25 -0400 (EDT)
On Sat, 11 Jul 1998, Mike Rosing wrote:
> If P is the number of states accessable to a system, then the entropy S
> is given by S = k ln(P) where k is a constant. Entropy is a measure of
> the number of states accessable to a system. Shannon tosses in a minus
> sign, but is measuring the same thing, the total number of chacters is
> the number of accesible states for a communications system.
>
> In the above assumptions, what do you mean by entropy?
Entropy for cryptographic purposes is a measure of the number of possible
states (therefore, of uncertainty) from the point of view of the best
attacker. To be most correct, we should refer to conditional entropy --
the entropy of a system conditional on the information available to any (or
the best) attacker.
Carl M. Ellison cme@acm.org http://www.clark.net/pub/cme
PGP: E0414C79B5AF36750217BC1A57386478 & 61E2DE7FCB9D7984E9C8048BA63221A2
``Officer, officer, arrest that man! He's whistling a dirty song.''
Jean Ellison (aka Mother)
The following archive was created by hippie-mail 7.98617-22 on Fri Aug 21 1998 - 17:20:17 ADT