The Evolution from Plain Text to Modern Hashing

The history of password storage reads like a catalog of security failures and hard-learned lessons. Early systems stored passwords in plain text, a practice that catastrophically exposed user credentials whenever databases were compromised. The introduction of one-way hashing functions seemed to solve this problem—passwords could be verified without storing the actual password. However, the deterministic nature of simple hashing created new vulnerabilities.

MD5 and SHA-1, once considered secure for password hashing, fell victim to increasing computational power and sophisticated attack techniques. Rainbow tables—precomputed tables of hash values for common passwords—made cracking simple hashed passwords trivial. The speed of these algorithms, originally considered a feature, became a critical weakness as attackers could compute billions of hashes per second using specialized hardware.

The fundamental realization that shaped modern password storage is that password hashing must be computationally expensive by design. Unlike other cryptographic operations where speed is desirable, password hashing benefits from deliberate slowness. This computational cost must be tunable to maintain security as hardware capabilities advance, leading to the development of adaptive hashing algorithms specifically designed for password storage.