The Evolution of Password-Specific Hashing

Password-specific hashing algorithms emerged from recognizing that password security requires different properties than general cryptographic hashing. While traditional hash functions optimize for speed, password hashers deliberately slow computation through techniques like key stretching, memory-hard functions, and tunable work factors. This paradigm shift acknowledges that passwords, unlike arbitrary data, come from a limited and predictable space requiring special protection.

The design principles for password hashing algorithms include computational expense to slow brute force attacks, memory requirements to prevent massive parallelization, salt integration to defeat precomputed attacks, and parameter tunability to maintain security as hardware improves. These algorithms transform the economics of password cracking, making attacks expensive in terms of time, hardware, and electricity costs.

Modern password hashers also consider side-channel resistance, ensuring that password verification time doesn't leak information about password content. They provide standardized formats for storing hashed passwords with their parameters, enabling systems to verify passwords even as security parameters evolve. This forward compatibility ensures that security can improve without breaking existing authentications.