• reinei@lemmy.world
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    5 months ago

    Okay first of all this message is really nicely written to explain multi collision attacks! (I knew some stuff about hashing and collision attacks before but not about multi collision and why that would be really useful here.)

    However, I first thought they were looking for inputs which basically preserve a known state and then generating an alphabet with those kinds of blocks (basically have one for each symbol and up to n additional blocks to “reset” the state to the known value) because that could shrink the size of stored blocks by a lot (I’d imagine).

    But now I am wondering if that’s even possible currently (even with an algorithm as “broken” as MD5 has become now)?

    • Natanael@slrpnk.net
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      5 months ago

      That’s a second pre-image attacks when you’re targeting existing state (attacking hash values of existing data by creating a second file matching it). For some reason even with MD5 that’s still infeasible - but collision attacks where you don’t have a target output value, but instead have partial target inputs which need to have the same output hash, are however practical and fast.