sergueyz at gmail.com
Fri Dec 3 23:51:05 CET 2010
2010/12/4 Permjacov Evgeniy <permeakra at gmail.com>:
>> near cryptographic) security. To quote Wikipedia again: "The avalanche
>> effect is evident if, when an input is changed slightly (for example,
>> flipping a single bit) the output changes significantly (e.g., half
>> the output bits flip)."
> This simply means, that active set of bits must be at least of the size
> of final value and value to be added must be added somehow to every byte
> in active set. The simplest way to do it is multiplication of vector
> [active-state-bits++current-byte] and some matrix of size [resulting
> bytes count|resulting bytes count + 1] (of cource, not in floating-point
> math, but, for example, using modulo-256 arithmetic or even hand-coded
> tables for "mul" and "sum"). This, of course, means, that byte-streaming
> hashes needs some initial seed (that must be paired with resulting value
> to check) and that every byte will cause much operations to perform,
> resulting in poor performance. So, the conclusion is: byte-streaming
> hashes are possible, but because of requirements definitly will have
> poor performance, much worse then block ones. Am I correct?
I think you are correct.
The note about matrices is interesting one.
The total matrix should be dense, but we could factor it. For example,
by multiplying two N wide and M wide band matrices we will get (N+M)
wide band matrix.
You are free to choose multiplication and addition operations, like
addition could be XOR and multiplication could be ROTATE_LEFT (like in
I did a little experiment: http://thesz.mskhug.ru/svn/cryptomatrix/
Just to demonstrate interesting properties of your suggestion.
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