It always confused me that people would create a random salt for a plaintext password they were about to encrypt, and somehow they were able to compare an entered password with the encrypted one and compare for similarity. As you will see from this script, what happens is that whatever you choose for a 2 character "salt" is always the same as the first two characters of the encrypted password. Therefore, all you have to do is take the plaintext password and use the _encrypted password_ as the salt, to recreate the entire encrypted password as long as the plaintext password is the same as the one that was originally entered. 


my $password = 'password';

my $encrypted_password = crypt $password, 'AB';

printf "password: %s encrypted_password: %s\n",
  $password, $encrypted_password;


printf "
crypt(password,AB): %s
encrypted_password: %s
crypt(password,BC): %s
crypt(password,encrypted_password): %s
\n",
  crypt($password,'AB'),
  $encrypted_password,
  crypt($password,'BC'),
  crypt($password,$encrypted_password);

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In reply to Understanding crypt() by princepawn

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