The encrypt function encrypts a string using the key generated by
    the setkey function.

    The first argument to encrypt is a character array of length 64
    containing 0s and 1s. The argument array is modified in place
    to a similar array representing the bits of the argument after
    having been subjected to the DES algorithm using the key set by
    setkey.

    The second argument, edflag, determines whether the first
    argument is encrypted or decrypted: if edflag is 0, the first
    argument array is encrypted; if nonzero, it is decrypted.

    No value is returned.

    See also crypt and setkey.