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UnixCrypt(3pm) User Contributed Perl Documentation UnixCrypt(3pm)
NAME
Crypt::UnixCrypt - perl-only implementation of the "crypt" function.
SYNOPSIS
use Crypt::UnixCrypt;
$hashed = crypt($plaintext,$salt);
# always use this module's crypt
BEGIN { $Crypt::UnixCrpyt::OVERRIDE_BUILTIN = 1 }
use Crypt::UnixCrypt;
DESCRIPTION
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.
COPYRIGHT
This module is free software; you may redistribute it and/or modify it under the same
terms as Perl itself.
AUTHORS
Written by Martin Vorlaender, martin AT radiogaga.de, 11-DEC-1997. Based upon Java
source code written by jdumas AT zgs.com, which in turn is based upon C source code written
by Eric Young, eay AT psych.au.
CAVEATS
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}.
SEE ALSO
perl(1), perlfunc(1), crypt(3).
perl v5.32.0 2021-01-05 UnixCrypt(3pm)
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On Apache
Under GNU General Public License
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