v4169sgr has asked for the wisdom of the Perl Monks concerning the following question:

I use Perl 5.10 ActivePerl 5.14 on win7. I am a humble user, and don't really understand what I am doing.

I have a requirement to connect to a remote host and send locally encrypted messages, using DES ECB mode encryption. This is not my choice, but a part of the requirement. I am trying to find out how to implement DES ECB mode encryption simply in Perl.

I do not have access to a C compiler, and cannot be the local administrator on my machine. I don't have download rights either, but can copy / paste source from CPAN into .pm files in my C:. I have copied the source for DES_PP.pm and ECB.pm to C:\Perl 5.10\lib\Crypt\ from CPAN. I've chosen DES_PP.pm as my understanding is that I don't need a C compiler to use it.

I need to make sure that I am using the ECB hex encryption function correctly. My code currently looks like this:

use Crypt::ECB qw(encrypt decrypt encrypt_hex decrypt_hex);
my $ascii_key = "0123456789abcdef";
my $plain_text = "Now is the time for all ";
print encrypt_hex($ascii_key,"DES_PP",$plain_text,"0");

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This 'works' in that it runs without errors, but produces output:

9a8836c3209081ed369a03f8b488a2ef3c85885f76d95430

From the example I am using in the original DES ECB mode specification (FIPS 81), I should see:

3fa40e8a984d48156a271787ab8883f9893d51ec4b563b53

What am I doing wrong?

Thanks in advance for all responses. Yes, I know there are much better ways of achieving encrypted traffic, and I know too that I should really do things the proper way via full local installation and C compilers etc, but I can't do any of that because of local policies, and still need to solve the problem.

Replies are listed 'Best First'.
Re: DES ECB mode using DES_PP
by Corion (Patriarch) on Aug 29, 2014 at 08:45 UTC

    The module expects the key to be in bytes, not in hexadecimal nibbles:

    use strict;
use Crypt::ECB qw(encrypt decrypt encrypt_hex decrypt_hex);

my $ascii_key = "0123456789abcdef";
my $key= "\x01\x23\x45\x67\x89\xab\xcd\xef";

my $plain_text = "Now is the time for all ";
my $expected= '3fa40e8a984d48156a271787ab8883f9893d51ec4b563b53';

my $result= encrypt_hex($key,"DES_PP",$plain_text,0);

if( $result eq $expected ) {
    print "Yay\n";
} else {
    print "Got     : $result\n";
    print "Expected: $expected\n";
};

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[reply]
[d/l]

      This works exactly as intended - thank you!

      Gosh, don't I feel stupid now :P

[reply]

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