4 ms·

though you could say this about any system that uses hashing. if sha256 or 512 is used, the likelihood of collisions with other functioning code, especially cod

though you could say this about any system that uses hashing. if sha256 or 512 is used, the likelihood of collisions with other functioning code, especially code that would yield useful xss seems impossibly small.

moe 12y ago
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.

moe 12y ago

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.