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/;

my $debug = 1 if @ARGV;

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

my @check_polys = ( 0x0000 .. 0xffff );
@check_polys = ( 32833, 43271, 32833, 43271, 19299, 35925, 47123, 49319, 56971 );

my @check_offset = ( 0,1,2,3 );
@check_offset = ( 1 ); # skip first, second always zero

my $found_polys;

sub check_crc {
        my ( $poly, $bytes, $wanted ) = @_;
        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
                #width=>16, init=>0xffff, xorout=>0, refout=>1, poly=>$poly, refin=>0 # ccitt
        );
        $ctx->add( $bytes );
        my $try = $ctx->digest;
        my $str = pack('n*', $try);
        warn "## check_crc( $poly, ",dump($bytes)," ) = ",dump( $str, $wanted ) if $debug;
        return $str eq $wanted;
}

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

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

        foreach my $o ( @check_offset ) {
                my $b = substr( $bytes, $o );

                foreach my $poly ( @check_polys ) {

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

                        if ( check_crc( $poly, $b, $crc ) ) {
                                warn "HIT: $o poly: $poly\n";
                                $found_polys->{$poly}->{$o}++;
                        }
                }
        }
}

print "FOUND polys = ", dump( $found_polys );
1	#!/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	my $debug = 1 if @ARGV;
13
14	sub hex2b {
15	my $hex = shift;
16	return map { hex($_) } split(/\s+/, $hex);
17	}
18
19	my @check_polys = ( 0x0000 .. 0xffff );
20	@check_polys = ( 32833, 43271, 32833, 43271, 19299, 35925, 47123, 49319, 56971 );
21
22	my @check_offset = ( 0,1,2,3 );
23	@check_offset = ( 1 ); # skip first, second always zero
24
25	my $found_polys;
26
27	sub check_crc {
28	my ( $poly, $bytes, $wanted ) = @_;
29	my $ctx = Digest::CRC->new(
30	#width=>16, init=>0xffff, xorout=>0, refout=>1, poly=>0x1021, refin=>0 # ccitt
31	#width=>16, init=>0, xorout=>0, refout=>1, poly=>0x8005, refin=>1 # crc16
32	#0x8408,
33	#0xa001,
34	width=>16, init=>0, xorout=>0, refout=>1, poly=>$poly,refin=>1
35	#width=>16, init=>0xffff, xorout=>0, refout=>1, poly=>$poly, refin=>0 # ccitt
36	);
37	$ctx->add( $bytes );
38	my $try = $ctx->digest;
39	my $str = pack('n*', $try);
40	warn "## check_crc( $poly, ",dump($bytes)," ) = ",dump( $str, $wanted ) if $debug;
41	return $str eq $wanted;
42	}
43
44	foreach (
45	'D5 00 05 04 00 11 8C 66',
46	'D6 00 05 FE 00 05 FA 40',
47	) {
48	my $hex = $_;
49	$hex =~ s/\s+//g;
50
51	my $bytes = pack('H*', substr($hex, 0, -4));
52
53	warn "?? guess crc ",substr($hex,-4);
54	my $crc = pack('H4', substr($hex,-4));
55
56	warn "input $_ => ",dump( $bytes, $crc );
57
58	foreach my $o ( @check_offset ) {
59	my $b = substr( $bytes, $o );
60
61	foreach my $poly ( @check_polys ) {
62
63	print "## poly $poly\n" if $poly % 1000 == 0;
64
65	if ( check_crc( $poly, $b, $crc ) ) {
66	warn "HIT: $o poly: $poly\n";
67	$found_polys->{$poly}->{$o}++;
68	}
69	}
70	}
71	}
72
73	print "FOUND polys = ", dump( $found_polys );