Cryptography/Breaking Hash Algorithms
Hashes are one of the more difficult, from a cryptography perspective, things to break. This is because of their very nature, being designed so that theoretically no algorithm may be made that will reverse a hash from its final state, back to its original state. If effect, this relationship is not observed: .
Attacks still exist against it. Even though the hashes can not be reversed, the methods for computing hashes are widely known so it allows for many of the other mentioned attacks to succeed: Brute Force, Frequency Analysis, Social Engineering and Coercion and Birthday Attack. Also, it should be mentioned that some hashes, md4, md5, sha-0 noteably have been found to have collisions that allow one to take an existing hash and compute a value that, once been hashed, will yield that value. This means that one can create other values that may or may not be the actual original but since it brings about the same hash it allows exploitation.