4 ms·

Better yet, use multiple hashes. Finding a simultaneous collision in sha256 and md5 seems pretty unlikely.

• lmm 12y ago
  No. This is bad advice, do not do this; it comes up every time there's a problem with a hash algorithm. The equivalent number of bits in a hashing algorithm designed as such (e.g. sha-384) will be substantially more secure than sha256+md5.
  • moe 12y ago
    That's not the point. The point is that you don't want to stand on only one leg when a flaw in that leg may be discovered in the future. Admittedly MD5 was a poor example from me in that light... A more realistic mix might be: sha256+RIPEMD160+Whirlpool. Or, in crypto-speak: Concatenating outputs from multiple hash functions provides collision resistance as good as the strongest of the algorithms included in the concatenated result. [1] [1] http://en.wikipedia.org/wiki/Cryptographic_hash_function#Concatenation_of_cryptographic_hash_functions http://en.wikipedia.org/wiki/Cryptographic_hash_function#Con...
    • lmm 12y ago
      Even a very serious attack against SHA-512 would be unlikely to render it as weak as RIPEMD-160 (compare even e.g. MD4, which is pretty thoroughly broken but the attacks still take compute time). If you have the bits, it's better to spend them on a longer hash rather than more hashes.
      • moe 12y ago
        Even a very serious attack against SHA-512 would What makes you think you can predict the consequences of an attack against SHA-512? Don't put all your eggs in one basket.
        • lmm 12y ago
          > What makes you think you can predict the consequences of an attack against SHA-512? 70 years of cryptographic history. > Don't put all your eggs in one basket. Don't use cryptographic primitives in ways they weren't designed for. That's a surefire recipe for disaster.