The crypt function generates an encoded version of a password.
    It is based on the NBS Data Encryption Standard, with variations
    intended to frustrate use of hardware implementations of the DES
    for key search.

    The first argument to crypt is normally a user's typed password.
    The second is a 2-character string chosen from the set [a-zA-Z0-
    9./]. The salt string is used to perturb the DES algorithm in one
    of 4096 different ways, after which the password is used as the
    key to encrypt repeatedly a constant string. The returned value
    points to the encrypted password, in the same alphabet as the
    salt. The first two characters are the salt itself.

    The return value from crypt points to a static data area whose
    content is overwritten by each call.

    See also encrypt and setkey.