Hashing

The process of converting a given key into another value. A hash function is used to generate the new value according to a mathematical algorithm.

Hashing is the process of converting input data of arbitrary size into a fixed-size output (called a hash or digest) using a mathematical function. A good hash function produces outputs that appear random, and even a small change in input produces a completely different hash. Hash functions are deterministic: the same input always produces the same output.

Common hash algorithms include SHA-256, SHA-3, and BLAKE2 for general-purpose hashing, and bcrypt, scrypt, and Argon2 for password hashing. Cryptographic hash functions are designed to be one-way (computationally infeasible to reverse) and collision-resistant (hard to find two inputs with the same output).

In API security, hashing is used extensively. API keys and passwords are stored as hashes rather than plaintext. HMAC (Hash-based Message Authentication Code) is used to verify the integrity and authenticity of API requests. Content hashing enables cache validation through ETags, allowing API gateways to determine whether a cached response is still valid without fetching the full response from the backend.