MD5 collision for known input

md5 collision
jabbink picture jabbink · Nov 18, 2012 · Viewed 10.3k times · Source

Is it possible to create a MD5 collision based on a known input value?

So for example I have input string abc with MD5 900150983cd24fb0d6963f7d28e17f72. Now I want to add bytes to string def to get the same MD5 900150983cd24fb0d6963f7d28e17f72.

(I know this is possible by bruteforcing and waiting a long time; I want to know if there is a more efficient way in doing this)

Answer

mata picture mata · Nov 19, 2012

Unitl now no algorithm has been discovered that allows you to find a matching input that will generate a given md5 hash.

What has been proven is that you can create md5 collisions quite easily, for example with what is known as chosen-prefix-collision: you can create two files yielding the same md5 hash by appending different data to a specified file. If you want to know more or get the program to try it, look here.

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