Crypt::UnixCrypt - perl-only implementation of the "crypt" function.
use Crypt::UnixCrypt;
$hashed = crypt($plaintext,$salt);
# always use this module's crypt
BEGIN { $Crypt::UnixCrpyt::OVERRIDE_BUILTIN = 1 }
use Crypt::UnixCrypt;
This module is for all those poor souls whose perl port answers to the use of
"crypt()" with the message `The
crypt() function is
unimplemented due to excessive paranoia.'.
This module won't overload a built-in "crypt()" unless forced by a
true value of the variable $Crypt::UnixCrypt::OVERRIDE_BUILTIN.
If you use this module, you probably neither have a built-in "crypt()"
function nor a
crypt(3) manpage; so I'll supply the appropriate
portions of its description (from my Linux system) here:
crypt is the password encryption function. It is based on the Data Encryption
Standard algorithm with variations intended (among other things) to discourage
use of hardware implementations of a key search.
$plaintext is a user's typed password.
$salt is a two-character string chosen from the set [a-zA-Z0-9./]. This string
is used to perturb the algorithm in one of 4096 different ways.
By taking the lowest 7 bit of each character of $plaintext (filling it up to 8
characters with zeros, if needed), a 56-bit key is obtained. This 56-bit key
is used to encrypt repeatedly a constant string (usually a string consisting
of all zeros). The returned value points to the encrypted password, a series
of 13 printable ASCII characters (the first two characters represent the salt
itself).
Warning: The key space consists of 2**56 equal 7.2e16 possible values.
Exhaustive searches of this key space are possible using massively parallel
computers. Software, such as
crack(1), is available which will search
the portion of this key space that is generally used by humans for passwords.
Hence, password selection should, at minimum, avoid common words and names.
The use of a
passwd(1) program that checks for crackable passwords
during the selection process is recommended.
The DES algorithm itself has a few quirks which make the use of the
crypt(3) interface a very poor choice for anything other than password
authentication. If you are planning on using the
crypt(3) interface for
a cryptography project, don't do it: get a good book on encryption and one of
the widely available DES libraries.
This module is free software; you may redistribute it and/or modify it under the
same terms as Perl itself.
Written by Martin Vorlaender,
[email protected], 11-DEC-1997. Based upon
Java source code written by
[email protected], which in turn is based upon C
source code written by Eric Young,
[email protected].
In extreme situations, this function doesn't behave like
crypt(3), e.g. when
called with a salt not in [A-Za-z0-9./]{2}.
perl(1),
perlfunc(1),
crypt(3).