Cryptography
Salt
Also known as: Cryptographic salt, Password salt
Definition
A unique random value combined with a password before hashing to defeat rainbow tables and ensure each user's hash is distinct.
Examples
- An Argon2id hash like $argon2id$v=19$m=65536,t=3,p=1$<base64-salt>$<base64-hash>.
- A unique 16-byte random salt generated per user during account creation.
Related terms
Pepper
A server-side secret combined with each password before hashing, held separately from the database to mitigate offline cracking after a hash leak.
Key Derivation Function (KDF)
A cryptographic function that derives one or more strong cryptographic keys from a secret input such as a password, shared secret or master key.
Argon2
A modern memory-hard password hashing function and KDF, winner of the 2015 Password Hashing Competition and specified in RFC 9106.
bcrypt
An adaptive password-hashing function based on the Blowfish cipher with a tunable cost factor, designed by Provos and Mazières in 1999.
Rainbow Table Attack
A precomputation attack that uses chains of hash and reduction functions stored in a compact table to invert unsalted password hashes much faster than brute force.
Cryptographic Hash Function
A deterministic one-way function that maps arbitrary-length input to a fixed-length digest, designed to be collision-, preimage-, and second-preimage-resistant.