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Showing posts from December, 2007

Another nail in the coffin for MD5

While collisions in MD5 hashes are nothing new, this most recent study by Wegner, Stevens, Lenstra (Article Link ) adds even more concern to the trustworthiness of an MD5 hash. If you can't trust a signed executable, what can you trust? I think nothing. Their technique however requires much premeditation. Its not as if you can create a collision on an existing executable. To be effective in a malicious way, it would require that you create two executables up front with the same hash. This is done by appending 832 bytes of useless data to the existing executables. As you can imagine, this would make it very easy for a criminal to create two versions of software, one with a backdoor, that have the exact same MD5 hash. Of course, it would be easy for them to get the good one signed and then create a download site with the malicious one. While this is somewhat sophisticated, i could definitely see this being utilized by the hack for money crews. It doesn't take much to get your so…