Crypt (C)

crypt is a function in the POSIX C library used to compute a hash of a user account password for storage and later verification on Unix systems. Its output is a single text string that encodes both a salt value and the hash result, and that identifies which underlying hashing algorithm produced it, defaulting to a traditional scheme if none is specified; this password record is normally kept in a text file rather than the plaintext password itself. More formally, crypt provides a family of key derivation functions used for password validation and storage.