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.IX Title "DES 3"
.TH DES 3 2026-08-11 "perl v5.42.2" "User Contributed Perl Documentation"
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.SH NAME
Crypt::DES \- Perl DES encryption module
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 5
\&        use Crypt::DES;
\&        my $key = pack("H16", "0123456789ABCDEF");
\&        my $cipher = Crypt::DES\->new($key);
\&        my $ciphertext = $cipher\->encrypt($plaintext);
\&        my $plaintext = $cipher\->decrypt($ciphertext);
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
The module implements the Crypt::CBC interface,
which has the following methods
.IP blocksize 4
.IX Item "blocksize"
.PD 0
.IP keysize 4
.IX Item "keysize"
.IP encrypt 4
.IX Item "encrypt"
.IP decrypt 4
.IX Item "decrypt"
.PD
.SH FUNCTIONS
.IX Header "FUNCTIONS"
.IP blocksize 4
.IX Item "blocksize"
Returns the size (in bytes) of the block cipher.
.IP keysize 4
.IX Item "keysize"
Returns the size (in bytes) of the key. Optimal size is 8 bytes.
.IP new 4
.IX Item "new"
.Vb 1
\&        my $cipher = Crypt::DES\->new($key);
.Ve
.Sp
This creates a new Crypt::DES BlockCipher object, using \f(CW$key\fR,
where \f(CW$key\fR is a key of \f(CWkeysize()\fR bytes.
.IP encrypt 4
.IX Item "encrypt"
.Vb 2
\&        my $cipher = Crypt::DES\->new($key);
\&        my $ciphertext = $cipher\->encrypt($plaintext);
.Ve
.Sp
This function encrypts \f(CW$plaintext\fR and returns the \f(CW$ciphertext\fR
where \f(CW$plaintext\fR and \f(CW$ciphertext\fR should be of \f(CWblocksize()\fR bytes.
.IP decrypt 4
.IX Item "decrypt"
.Vb 2
\&        my $cipher = Crypt::DES\->new($key);
\&        my $plaintext = $cipher\->decrypt($ciphertext);
.Ve
.Sp
This function decrypts \f(CW$ciphertext\fR and returns the \f(CW$plaintext\fR
where \f(CW$plaintext\fR and \f(CW$ciphertext\fR should be of \f(CWblocksize()\fR bytes.
.SH "Security Considerations"
.IX Header "Security Considerations"
This module is not deprecated as there may still be a reason to
encrypt and decrypt using DES. However, DES is known to be weak.
In 2026 a standard laptop can brute\-force a DES key in a few
days. \fBDO NOT use DES (or this module) with any expectation of
security\fR.
.SH EXAMPLE
.IX Header "EXAMPLE"
.Vb 6
\&        my $key = pack("H16", "0123456789ABCDEF");
\&        my $cipher = Crypt::DES\->new($key);
\&        my $ciphertext = $cipher\->encrypt("plaintex");  # NB \- 8 bytes
\&        print unpack("H16", $ciphertext), "\en";
\&        my $plaintext = $cipher\->decrypt($ciphertext);
\&        print $plaintext, "\en";
.Ve
.SH NOTES
.IX Header "NOTES"
Do note that DES only uses 8 byte keys and only works on 8 byte data
blocks.  If you\*(Aqre intending to encrypt larger blocks or entire files, 
please use Crypt::CBC in conjunction with this module.  See the
Crypt::CBC documentation for proper syntax and use.
.PP
Also note that the DES algorithm is, by today\*(Aqs standard, weak 
encryption.  CryptX (Crypt::Cipher::AES) is recommended if you
want to replace Crypt::DES in a Crypt::CBC use case.  Otherwise,
replacing it with something like Crypt::AuthEnc::GCM would be
recommended.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Crypt::AuthEnc::GCM
Crypt::Blowfish
Crypt::IDEA
.PP
Bruce Schneier, \fIApplied Cryptography\fR, 1995, Second Edition,
published by John Wiley & Sons, Inc.
.SH COPYRIGHT
.IX Header "COPYRIGHT"
The implementation of the DES algorithm was developed by,
and is copyright of, Eric Young (eay@mincom.oz.au).
Other parts of the perl extension and module are
copyright of Systemics Ltd ( http://www.systemics.com/ ).
Cross\-platform work and packaging for single algorithm 
distribution is copyright of W3Works, LLC.
.SH MAINTAINER
.IX Header "MAINTAINER"
This single\-algorithm package and cross\-platform code is 
maintained by Dave Paris <amused@pobox.com>.
.PP
Timothy Legge <timlegge@gmail.com> started maintaining
this module as of version 2.08.