Asymmetric Key Algorithms

Key stretching, or key strengthening, uses cryptography to make a weak key stronger by increasing the time that it takes to test each possible key. An algorithm is applied to the original key to produce an enhanced key. Key stretching provides a key of at least 128 bits.

Key stretching slows down an attacker because the attacker has to compute the stretching function for every guess in the attack. PGP, WPA, and WPA2 all use key stretching.