Quoting RFC #1321, Section 1:

"It is conjectured that it is computationally infeasible to produce
two messages having the same message digest, or to produce any
message having a given prespecified target message digest."

This conjecture has now been determined to be false. In fact, a single 
laptop can perform both these tasks in a few minutes using a suitable 
algorithm.

However, one might also conjecture that the probability of any two 
arbitrary messages having the same [MD5] hash code would be 2^(-128).

Does the existence of a collision-generation algorithm for MD5 
contradict this second conjecture?

(In othe words, it is possible to *maliciously* alter a message without 
affecting the MD5 hash, but what is the probability of an *accidental* 
modification going undetected? Is it 2^(-128)? Or is it some higher 
probability?)

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