3 ms·

Yikes. Surely in forensics you’d want the most collision resistant hashing tool available? Doesn’t the uniqueness guarantee the consistency?

• WrtCdEvrydy 6y ago
  That's kinda the issue, you only want to guarantee that the image didn't change (ie, noone planted anything and the chain of evidence from the crime scene to your nice forensics lab is untampered). I think once someone makes a tool that allows you to add a file to an image and have it resolve to the same hash (anti-forensics as a field), it will probably change. Most tools do offer dual MD5 and SHA256 support though.
  • wbl 6y ago
    That's a second preimage attack not a collision attack.
    • hyko 6y ago
      I thought a second preimage attach implied a collision attack?
      • SAI_Peregrinus 6y ago
        Yes but the reverse isn't true. Collisions don't imply second-preimage attacks, at least not at any practical difficulty.
  • hyko 6y ago
    you only want to guarantee that the image didn’t change But if the algorithm allows you to find hash collisions, you can’t guarantee that the image didn’t change based on the MD5 hash value? e.g. https://natmchugh.blogspot.com/2014/11/three-way-md5-collision.html?m=1 https://natmchugh.blogspot.com/2014/11/three-way-md5-collisi... Obviously that example is a chosen prefix collision, but this data is coming from an untrusted source after all, so there’s really nothing to stop the attacker choosing the prefix in advance and then publicly shredding trust in the hash at a later date. In practice it sounds like you’d also have a hash of the complete file system, but at this point you’d have to question what advantage there is to using MD5 at all. Attacks never get worse, only ever get better, and the last thing you’d want is for the dam to burst during a lengthy and important investigation.
    • WrtCdEvrydy 6y ago
      Yeah, I do wonder if the tooling to cause a full MD5 hash collision across the file system will come in the future.