crypt

See the current Perl documentation for crypt.

Here is our local, out-dated (pre-5.6) version:

crypt - one-way passwd-style encryption

crypt PLAINTEXT,SALT

Encrypts a string exactly like the crypt(3) function in the C library (assuming that you actually have a version there that has not been extirpated as a potential munition). This can prove useful for checking the password file for lousy passwords, amongst other things. Only the guys wearing white hats should do this.

Note that crypt() is intended to be a one-way function, much like breaking eggs to make an omelette. There is no (known) corresponding decrypt function. As a result, this function isn't all that useful for cryptography. (For that, see your nearby CPAN mirror.)

Here's an example that makes sure that whoever runs this program knows their own password:

    $pwd = (getpwuid($<))[1];
    $salt = substr($pwd, 0, 2);

    system "stty -echo";
    print "Password: ";
    chop($word = <STDIN>);
    print "\n";
    system "stty echo";

    if (crypt($word, $salt) ne $pwd) {
        die "Sorry...\n";
    } else {
        print "ok\n";
    }

Of course, typing in your own password to whoever asks you for it is unwise.