Create your own MD5 collisions

Question

I\'m doing a presentation on MD5 collisions and I\'d like to give people any idea how likely a collision is.

It would be good to have two blocks of text which hash t

Answer 1

I would take a look at Hashcash. With an effective hash algorithm, like md5, the time to calculate a collision to exponential with the number of bits. What Hashcash does is calculates partial collisions. That is, a match of say the lower 16 bits of the hash. To get the lower 16 bits to match, one would have to try hashing 2^15 different combinations on average. If you know how long it takes to come up with a 16, 24, or 32 bit collision, then you can easily calculate out the time for higher numbers of bits.