3 ms·

One thing that I always wondered about this approach: for (i = 0; i < 1000; i++) scrambled_password = HASH(scrambled_password) Aren't we weakenin

by jules 14y ago

One thing that I always wondered about this approach: for (i = 0; i < 1000; i++) scrambled_password = HASH(scrambled_password) Aren't we weakening the hash function? Presumably the hash function is not one-to-one, so if you iterate this for many iterations there is a danger that you could end up with a function that has a much higher probability of collisions?

yuvadam 14y ago
Why would you assume that? Persumably there should be no real reason why HASH(8_char_password) = 160_bit_hash should be less strong than HASH(160_bit_hash). Not only that, but most hashing algorithms already do several iterations before returning the hash.
- rfergie 14y ago
  I think the concern is that the hash function may converge.
- recursive 14y ago
  The space of the output of the hash as at most as big as the space of the input.
dchest 14y ago
There can be entropy loss. 1. http://crypto.stackexchange.com/questions/135/why-does-pbkdf2-xor-the-iterations-of-the-hash-function-together http://crypto.stackexchange.com/questions/135/why-does-pbkdf... 2. http://news.ycombinator.com/item?id=2005929 http://news.ycombinator.com/item?id=2005929
- tptacek 14y ago
  ... in a theoretical sense; it is comically unlikely to be a real-world concern.