The crypt() function encodes strings suitable for secure storage as passwords. It generates the password hash given the key and salt.

The key argument is the plain text password to be encrypted.

The crypt() function calls crypt_gensalt(3C) to generate the salt. If the first character of salt is "$", crypt() uses crypt.conf(4) to determine which shared module to load for the encryption algorithm. If the first character of salt is not "$", the algorithm described on crypt_unix(5) is used.

Upon successful completion, crypt() returns a pointer to the encoded string. Otherwise it returns a null pointer and sets errno to indicate the error.

The return value points to static data that is overwritten by each call.

The crypt() function will fail if:

EINVAL

An entry in crypt.conf is invalid.

ELIBACC

The required shared library was not found.

ENOMEM

There is insufficient memory to generate the hash.

ENOSYS

The functionality is not supported on this system.

The values returned by this function might not be portable among standard-conforming systems. See standards(5).

Applications should not use crypt() to store or verify user passwords but should use the functions described on pam(3PAM) instead.

See attributes(5) for descriptions of the following attributes:

passwd(1), crypt_genhash_impl(3C), crypt_gensalt(3C), crypt_gensalt_impl(3C), getpassphrase(3C), pam(3PAM), passwd(4), attributes(5), crypt_unix(5), standards(5)