viewvc.cgi/RFID/guess-crc.pl

#!/usr/bin/perl -w

# guess-crc.pl
#
# 09/28/08 21:54:24 CEST Dobrica Pavlinusic <dpavlin@rot13.org>

use strict;

use Digest::CRC qw(crc32 crc16 crcccitt crc crc8);
use Data::Dump qw/dump/;

sub hex2b {
        my $hex = shift;
        return map { hex($_) } split(/\s+/, $hex);
}

my @poly;
# ( 32833, 43271, 32833, 43271, 19299, 35925, 47123, 49319, 56971 );

foreach (
'D5 00 05 04 00 11 8C 66',
'D6 00 05 FE 00 05 FA 40',
) {
        my $hex = $_;
        $hex =~ s/\s+//g;

        my $bytes = pack('H*', substr($hex, 0, -4));

        warn "?? crc ",substr($hex,-4);
        my $crc   = pack('H4', substr($hex,-4));

        warn "input $_ => ",dump( $bytes, $crc );

        foreach my $o ( 0,1,2,3 ) {
                my $b = substr( $bytes, $o );

                foreach my $poly ( 0x0000 .. 0xffff ) {

                        print "## poly $poly\n" if $poly % 1000 == 0;

                        my $ctx = Digest::CRC->new(
                                #width=>16, init=>0xffff, xorout=>0, refout=>1, poly=>0x1021, refin=>0 # ccitt
                                #width=>16, init=>0,      xorout=>0, refout=>1, poly=>0x8005, refin=>1 # crc16
                                #0x8408,
                                #0xa001,
                                width=>16, init=>0, xorout=>0, refout=>1, poly=>$poly,refin=>1
                        );
                        $ctx->add( $b );
                        my $try = $ctx->digest;

                        my $v = pack('v*', $try);
                        my $n = pack('n*', $try);

                        if ( $v eq $crc or $n eq $crc ) {
                                warn "HIT: $o poly: $poly ",dump( $crc, $v, $n );
                                push @poly, $poly;
                        }
                }
        }
}

print "FOUND poly = ", dump( @poly );
1	dpavlin	7	#!/usr/bin/perl -w
2
3			# guess-crc.pl
4			#
5			# 09/28/08 21:54:24 CEST Dobrica Pavlinusic <dpavlin@rot13.org>
6
7			use strict;
8
9			use Digest::CRC qw(crc32 crc16 crcccitt crc crc8);
10			use Data::Dump qw/dump/;
11
12			sub hex2b {
13			my $hex = shift;
14			return map { hex($_) } split(/\s+/, $hex);
15			}
16
17			my @poly;
18			# ( 32833, 43271, 32833, 43271, 19299, 35925, 47123, 49319, 56971 );
19
20			foreach (
21			'D5 00 05 04 00 11 8C 66',
22			'D6 00 05 FE 00 05 FA 40',
23			) {
24			my $hex = $_;
25			$hex =~ s/\s+//g;
26
27			my $bytes = pack('H*', substr($hex, 0, -4));
28
29			warn "?? crc ",substr($hex,-4);
30			my $crc = pack('H4', substr($hex,-4));
31
32			warn "input $_ => ",dump( $bytes, $crc );
33
34			foreach my $o ( 0,1,2,3 ) {
35			my $b = substr( $bytes, $o );
36
37			foreach my $poly ( 0x0000 .. 0xffff ) {
38
39			print "## poly $poly\n" if $poly % 1000 == 0;
40
41			my $ctx = Digest::CRC->new(
42			#width=>16, init=>0xffff, xorout=>0, refout=>1, poly=>0x1021, refin=>0 # ccitt
43			#width=>16, init=>0, xorout=>0, refout=>1, poly=>0x8005, refin=>1 # crc16
44			#0x8408,
45			#0xa001,
46			width=>16, init=>0, xorout=>0, refout=>1, poly=>$poly,refin=>1
47			);
48			$ctx->add( $b );
49			my $try = $ctx->digest;
50
51			my $v = pack('v*', $try);
52			my $n = pack('n*', $try);
53
54			if ( $v eq $crc or $n eq $crc ) {
55			warn "HIT: $o poly: $poly ",dump( $crc, $v, $n );
56			push @poly, $poly;
57			}
58			}
59			}
60			}
61
62			print "FOUND poly = ", dump( @poly );