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# IP::Anonymous - Perl port of Crypto-PAn to provide anonymous IP addresses |
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# |
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# Copyright (c) 2005 John Kristoff . All rights |
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# reserved. This program is free software; you can redistribute it and/or |
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# modify it under the same terms as Perl itself. |
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package IP::Anonymous; |
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$VERSION = '0.04'; |
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require 5.001; |
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# base extensions and modules |
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use strict; # force us to code defensively |
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use warnings; # do not let laziness go unnoticed |
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use vars qw($VERSION); # package scope global vars |
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use Carp; # make errors the caller's problem |
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use Socket; # for convenient dotted quad handling routines |
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# additional modules |
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use Crypt::Rijndael; # the Rijndael crypto magic |
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# module scope vars |
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my $m_pad; # 2nd 128 bits of user key used for secret padding |
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my $ecb; # electronic codebook mode (default) object |
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my $first4bytes_pad; # 1st 4 bytes of secret pad in "network" order |
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# initialize |
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sub new { |
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my $package = shift; |
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my @key = @_; # expected key is 32 8-bit unsigned ints |
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my $m_key; # 1st 128 bits of user key used for cipher |
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# 1st 128 bits of key used as secret key for Rijndael cipher |
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$m_key = pack("C16", @key[0..15]); |
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# 2nd 128 bits of key used for secret padding |
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$m_pad = pack("C16", @key[16..31]); |
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# init the key |
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$ecb = new Crypt::Rijndael $m_key; |
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# encrypt the 128-bit secret pad |
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$m_pad = $ecb->encrypt($m_pad); |
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# first four bytes of secret pad in "network" (big-endian) order |
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$first4bytes_pad = unpack("N", $m_pad); |
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return bless({}, $package); |
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} |
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# generate a bit using the Rijndael cipher for each of the 32 bit address |
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# msb bits taken from original address, remaining bits are from m_pad |
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sub anonymize { |
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my $package = shift; |
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my $address = shift; # expect dotted quad string |
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my $first4bytes_input; # used to handle the byte ordering problem |
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my @rin_input = (); # psuedorandom Rijndael cipher used each round |
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my $rin_output; # encrypted byte result at each round |
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my $result = 0; # initialize psuedorandom one time pad |
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# rudimentary check for correctly formatted dotted quad |
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if($address !~ /^\d{1,3}(?:\.\d{1,3}){3}$/) { |
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croak("ERROR [".__LINE__."]: invalid IP address format\n"); |
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return; |
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} |
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# convert dotted quad to long in "network" (big-endian) order |
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$address = unpack("N", pack("C4", split /\./, $address)); |
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# Rijndael cipher used to obtain each of the 32 anonymized bits |
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@rin_input = unpack("C16", $m_pad); |
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# init input with encrypted pad |
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$rin_input[0] = ($first4bytes_pad >> 24); |
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# mask off excess bits for 64-bit systems in left shift |
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$rin_input[1] = (($first4bytes_pad << 8 & 0xffffffff) >> 24); |
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$rin_input[2] = (($first4bytes_pad << 16 & 0xffffffff) >> 24); |
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$rin_input[3] = (($first4bytes_pad << 24 & 0xffffffff) >> 24); |
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# get an 8-bit byte |
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$rin_output = unpack("C", $ecb->encrypt(pack("C16", @rin_input))); |
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# only the first bit of rin_output is used for each round |
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$result |= ($rin_output >> 7) << 31; |
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# loop through remaining 31 bits |
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for (my $position=1; $position <= 31; $position++) { |
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$first4bytes_input = (($address >> (32-$position)) << |
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(32-$position)) | |
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# mask off excess bits for 64-bit systems |
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(($first4bytes_pad << $position & 0xffffffff) >> |
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$position); |
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$rin_input[0] = ($first4bytes_input >> 24); |
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# mask off excess bits for 64-bit systems in left shift |
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$rin_input[1] = (($first4bytes_input << 8 & 0xffffffff) >> 24); |
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$rin_input[2] = (($first4bytes_input << 16 & 0xffffffff) >> 24); |
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$rin_input[3] = (($first4bytes_input << 24 & 0xffffffff) >> 24); |
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# get an 8-bit byte |
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$rin_output = unpack("C", $ecb->encrypt(pack("C16", @rin_input))); |
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# only the first bit of rin_output is used for each round |
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$result |= ($rin_output >> 7) << (31-$position); |
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} |
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# return anonymized, prefix-preserved address as a dotted quad string |
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return inet_ntoa(pack("N", $result ^ $address)) |
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} |
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1; |
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__END__ |