Roll your DSA signatures

This node How to Make Crypt::DSA use a your key to sign something got me thinking about how to extend Crypt::DSA's potential, to make public and private keys, for signing verification. The script below, will verify 2 ways, once with scalars inside the script, and once from files. The generated sig, is actually binary, so note the base64 encoding of it, for attachment to emails, etc. I must thank sisyphus for the trick of reblessing a hash back into an object. This is the critical part of the script, where the public and private keys are generated. The docs for Crypt::DSA don't show how to separate them,( and you wouldn't want to be distributing your private key in the public PEM file. :-)

#!/usr/bin/perl
use warnings;
use strict;
use Crypt::DSA;
use Crypt::DSA::Key;
use MIME::Base64 qw( encode_base64 decode_base64 );

my $dsa = Crypt::DSA->new;

# use to generate your keys below
# my $key = $dsa->keygen(Size => 512, Verbosity => 1); 
# print ref $key; foreach my $k (keys %{$key}) { 
# print $k . "=" . $key->$k . " "; 
# }

# hard code in the above generated numbers.
my %key_priv;
 $key_priv{'priv_key'} = '86493656493674673971107878679102456068174181
+0216'; 
 $key_priv{'p'} = '103389578900933505962259092511631192256092079077336
+779855585334041474848850089585441001014183922540716749810264398731049
+49464720186311018367111795638927603'; 
 $key_priv{'g'} = '295468312836227549163017971559304985039133262378345
+815627315465892672058916494919915988882646491840732863667119568864913
+0131612326212886632087281832722137'; 
 $key_priv{'q'} = '1001831165198829652697436093010198645746872403487';
+ 
# $key_priv{'pub_key'} = ''; #don't include in private key 

my %key_pub;
# $key_pub{'priv_key'} = ''; #don't include in public key 
 $key_pub{'p'} = $key_priv{'p'}; 
 $key_pub{'g'} = $key_priv{'g'}; 
 $key_pub{'q'} = $key_priv{'q'};
 $key_pub{'pub_key'} = '1323460927720994618070448727574663888688993575
+715081267508071818636049670044713302408747578850296432590020771929699
+912452512506924349344334420749206004502'; 

my $msg = "xxxxxxxxxxxxxxxxxx\n" x 40;
open(FH,">msg") or die "$!\n";
print FH $msg;
close FH;

my $k_priv = \%key_priv;
bless($k_priv, "Crypt::DSA::Key");

my $sig = $dsa->sign(Message=>$msg, 
                     Key => $k_priv);

my $sig_ser = $sig->serialize;
open(FH,">sig") or die "$!\n";
print FH encode_base64($sig_ser); #need base64 encoding
close FH;                         #of binary sig

my $pem_priv = $k_priv->write( Type => 'PEM' );
open(FH,">key_priv") or die "$!\n";
print FH $pem_priv;
close FH;

###############################################
#verify with pub_key from internal variables

my $k_pub = \%key_pub;
bless($k_pub, "Crypt::DSA::Key");

my $pem_pub = $k_pub->write( Type => 'PEM' );
open(FH,">key_pub") or die "$!\n";
print FH $pem_pub;
close FH;

my $verified = $dsa->verify(
     Message   => $msg,
     Signature => $sig,
     Key       => $k_pub,
);
print "verified internally->$verified\n";
#############################################
#verify with pub_key from files
my $msg_in;
open (FH,"< msg");
read( FH, $msg_in, -s FH );
close FH;

my $sig_in;
open (FH,"< sig");
read( FH, $sig_in, -s FH );
close FH;

my $dsa1 = Crypt::DSA->new;

my $key_pub = Crypt::DSA::Key->new( Type => 'PEM', 
                        Filename => 'key_pub'); 

my $sig_o = Crypt::DSA::Signature->new( Content => decode_base64( $sig
+_in ) );

my $verified1 = $dsa1->verify(
     Message   => $msg_in,
     Signature => $sig_o,
     Key       => $key_pub,
);
print "verified thru files->$verified1\n";
#############################################
[download]

I'm not really a human, but I play one on earth. flash japh

Comment on Roll your DSA signatures Download Code

Replies are listed 'Best First'.
Re: Roll your DSA signatures by zentara (Cardinal) on Feb 24, 2006 at 21:53 UTC
The script above was for demonstrating the basics. Here are a set of scripts, derived from the above, to do it in a more useful manner...... gen_keys, sign-a-file,verify-a-file,check-key Read more... (4 kB) I'm not really a human, but I play one on earth. flash japh	[reply] [d/l]