Two programmes, different size, same MD5

Networking/Security Forums -> Cryptographic Theory and Cryptanalysis - Internal and Transmission Security

Author: anon_private PostPosted: Fri Oct 29, 2010 12:50 pm    Post subject: Two programmes, different size, same MD5
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Hi,

I recently downloaded two programmes, one is a supposed update of the other, one is larger than the other. They have different icons, but the md5's are the same.

I assume that they are the same programme because the md5's are the same. What puzzles me is the the file sizes are different.

Any ideas?

Do the icons count in the md5?

Thanks

Author: Fire AntLocation: London PostPosted: Mon Nov 01, 2010 9:47 pm    Post subject:
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Quote:
Do the icons count in the md5?
This depends. You can choose for Windows to display an icon which is not included in the resources section of the executable.

If the file sizes are different they you have what is known as a message digest collision. It is not common to find a collision in the wild but MD5 has known issues with regards finding collisions.

Have you tried using another digest algorithm like SHA?

Fire Ant

Author: anon_private PostPosted: Tue Nov 02, 2010 2:02 pm    Post subject:
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Thanks for responding.

I have now discovered that the programmes are indeed the same.

One was simply compressed.

On copying the compressed file it expanded to give the same file that I had originally on the machine.

They are now both the same size and have the same md5.

Best wishes.

A



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