tools/rfidtest.pl

   1 #!/usr/bin/env perl
   2 # -samy kamkar, rfid@samy.pl
   3
   4 use strict;
   5
   6 die "usage: $0 <file with data> <binary to search for>\n" unless @ARGV == 2;
   7
   8 my ($file, $search) = @ARGV;
   9 $search =~ s/\s//g;
  10
  11 # sure, these aren't perfect, but simplifies usability if you know what you're doing
  12 # if in doubt, use binary
  13
  14 # binary, cool
  15 if ($search =~ /^[01]+$/) { }
  16 # decimal
  17 elsif ($search =~ /^\d+$/)
  18 {
  19     $search = unpack("B*", pack("N", $search));
  20     $search =~ s/^0*//;
  21 }
  22 # hex
  23 elsif ($search =~ /^[\da-fA-F]+$/)
  24 {
  25     $search = unpack("B*", pack("H*", $search));
  26     $search =~ s/^0*//;
  27 }
  28 # ascii
  29 else
  30 {
  31     $search = unpack("B*", $search);
  32     $search =~ s/^0*//;
  33 }
  34
  35
  36 # read file contents
  37 open(F, "<$file") || die "Can't read $file: $!";
  38 my $data = join("", <F>);
  39 close(F);
  40
  41 # convert to binary
  42 $data =~ s/\s//g;
  43 # binary, great
  44 if ($data =~ /^[01]+$/) { }
  45 elsif ($data =~ /^[\da-fA-F]+$/)
  46 {
  47     $data = unpack("B*", pack("H*", $data));
  48     $search =~ s/^0*//;
  49 }
  50 else
  51 {
  52     die "Seriously. What sort of data is this file? Binary or hex only please.\n";
  53 }
  54
  55
  56 # search every method we know how
  57 print "Testing normally...\n";
  58 test_all($data, $search);
  59
  60 print "Testing with flipped bits...\n";
  61 test_all($data, $search, 1);
  62
  63 # now try manchester demodulating
  64 my @bits = split(//, $data);
  65 my $man;
  66 my $last = 0;
  67 for (my $i = 1; $i < @bits; $i++)
  68 {
  69     # if we changed, flip our bit
  70     if ($bits[$i-1] == 1)
  71     {
  72         $last ^= 1;
  73     }
  74     $man .= $last;
  75 }
  76
  77 print "Testing with manchester demodulation...\n";
  78 test_all($man, $search);
  79
  80 print "Testing with flipped manchester demodulation...\n";
  81 test_all($man, $search, 1);
  82
  83
  84 sub test_all
  85 {
  86     my ($data, $search, $flip) = @_;
  87
  88     if ($flip)
  89     {
  90         $data =~ s/(.)/$1 ^ 1/eg;
  91     }
  92
  93     # first just see if our data is in the stream
  94     if ($data =~ /$search/)
  95     {
  96         print "Found $search in our stream ($data)\n";
  97     }
  98
  99     # try removing parity every 4 and 8 bits
 100     foreach my $parity (4, 8)
 101     {
 102         # try removing a parity bit every $parity bits
 103         # test by cutting off a bit at a time in case we're in the wrong bit position
 104         my $tmp = $data;
 105         foreach (1 .. $parity)
 106         {
 107             my $test = $tmp;
 108             $test =~ s/(.{$parity})./$1/g;
 109
 110             if ($test =~ /$search/)
 111             {
 112                 print "Found $search with parity every " . ($parity + 1) . "th bit, round $_ out of $parity ($test)\n";
 113             }
 114
 115             # chop of a bit to change our bit position next round
 116             $tmp =~ s/^.//;
 117         }
 118     }
 119 }