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Reversing hashes, even thoroughly broken ones, is still quite impractical - it's collision attacks that you have to watch out for. Of course, you don't break p
by JoachimSchipper 15y ago
Reversing hashes, even thoroughly broken ones, is still quite impractical - it's collision attacks that you have to watch out for.
Of course, you don't break password hashes by reversing the hash, you break password hashes by just trying (variations on) dictionary words until one matches the hash. For that purpose, SHA-256 is not a good choice, since it's too fast - use PBKDF2/bcrypt.
- SoftwareMaven 15y agoReversing a hash is impossible, so a collision is "reversing" it. All that really matters is that you've got something that the auth system will think is the right password.
- JoachimSchipper 15y agoYou're confusing a collision (find any x, y such that f(x) = f(y)) and a second preimage attack (find any x such that f(x) = y for some particular y). The latter is much more difficult, but the former can still be used - see "rogue CA".