Re: [CI] Re: Finding collision resistant hash functions
At 11:18 PM 7/7/03 -0700, Sarad AV wrote:
Lets say we are using SHA-1 and i hash 2^80 messages.What I am looking for is a compression function such that the chances of collision in the message digest obtained by hashing these 2^80 messages is collision free or very low probability of collision.How do we make such a compression function?
You don't need one with a good hash function. Consider a hash made out of a block cipher digesting the input. A block cipher has the property that any one bit difference in input will change half the output bits on average. There's nothing gained by increasing the input entropy (compressing).
hi,
There's nothing gained by increasing the input entropy (compressing
http://www.itl.nist.gov/fipspubs/fip180-1.htm For t = 0 to 79 do TEMP = (A)<<5 + f(B,C,D) + E + Wt + Kt; E = D; D = C; C = B<<30; B = A; A = TEMP; Thats what I meant by the compression function. I am not trying to increase the input entropy. I was looking for such a compression function such that the chances of collision in the message digest obtained by hashing these 2^80 messages is collision free or very low probability of collision or in other words I dont want the birthday attack to work on it. If i hash 2^80 messages they should be equidistibuted in such a manner that it does not affect the security of the algorithm. --- "Major Variola (ret)" <mv@cdc.gov> wrote:
At 11:18 PM 7/7/03 -0700, Sarad AV wrote: A block cipher has the property that any one bit difference in input will change half the output bits on average.
thank you. Sarath. __________________________________ Do you Yahoo!? SBC Yahoo! DSL - Now only $29.95 per month! http://sbc.yahoo.com
participants (2)
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Major Variola (ret) -
Sarad AV