FCP/Key/CHK.pm

=head1 NAME

Net::FCP::Key::CHK - manage CHK keys.

=head1 SYNOPSIS

 use Net::FCP::Key::CHK;

 my $key = new Net::FCP::Key::CHK;
 my $key = new_from_uri Net::FCP::Key::CHK $uri;
 my $key = new_from_data Net::FCP::Key::CHK $data, $metadata;
 ... more to come


=head1 DESCRIPTION

=head2 THE Net::FCP::Key::CHK CLASS

=over 4

=cut

package Net::FCP::Key::CHK;

use Carp;
use Digest::SHA1;
use MIME::Base64;

use Crypt::Rijndael;
use Crypt::Twofish;

use Net::FCP::Util;

no warnings;

=item my $key = new Net::FCP::Key::CHK;

Heavily under development, don't use :)

=cut

sub new {
   my $class = shift;

   bless { }, $class;
}

=item my $key = new_from_data Net::FCP::Key::CHK $metadata, $data[, $cipher];

Generate a CHK from the given data and metadata strings.

=cut

sub new_from_data {
   my ($class, $metadata, $data, $cipher) = @_;

   $class->new->set_data ($metadata, $data, $cipher);
}

sub rolling_hashpad($$$) {
   my $sha1 = $_[1];
   my $pad = "";
   my $dig;

   while ($_[2] > length $_[0]) {
      $sha1->add ($dig = $sha1->digest_noreset);
      $pad .= $dig;
      $_[0] .= $pad;
   }

   substr $_[0], $_[2], length $_[0], "";
}

sub encode_number($) {
   my $num = pack "N", $_[0];
   $num =~ s/^\x00+//;
   pack "n a*", length $num, $num;
}

sub set_data {
   my ($self, $metadata, $data, $cipher) = @_;

   $cipher ||= "Twofish";

   my $cipher_class = "Crypt::$cipher";

   $cipher_class->blocksize == 16 or die "only ciphers with a blocksize of 128 bits are supported";

   my $total_len = (length $metadata) + (length $data);
   my $padded_log = Net::FCP::Util::log2 $total_len, 10;
   my $padded_len = 1 << $padded_log;

   my $plaintext = "$metadata$data";

   # crypto key (hash) generation. this is an iterative
   # algorithm, but it is "unrolled" here for the
   # common keysize of 16 bytes.
   my $data_sha1 = Digest::SHA1->new->add ($plaintext);

   # only works for 128 bit keys
   my $k = new Digest::SHA1;
   $k->add ("\x00" x 1);
   $k->add ($data_sha1->clone->digest);

   my $hash = substr $k->digest, 0, 16; # extract leading 128 bit

   my $buf = "";

   $buf .= pack "n a20", 20, Digest::SHA1::sha1 $hash;

   $buf .= encode_number $total_len;
   $buf .= encode_number length $metadata;

   $buf .= "\x00\x00";

   rolling_hashpad $buf, Digest::SHA1->new->add ($buf), 1 << Net::FCP::Util::log2 length $buf;

   my $pcfb_cipher = $cipher_class->new ($hash);
   my $pcfb_reg = "\x00" x 16;

   my $pcfb_enc = sub  {
      my $length = length $_[0];
      my $enc = "";
      for (my $i = 0; $i < $length; $i += 16) {
         $enc .= $pcfb_reg = $pcfb_cipher->encrypt ($pcfb_reg) ^ substr $_[0], $i, 16;
      }
      $enc;
   };

   # buf length must be multiple of 16
   $buf = $pcfb_enc->($buf);

   my $senc = unpack "H*", $buf;

   rolling_hashpad $plaintext, $data_sha1, $padded_len;

   # plaintext length must be a multiple of 16, too
   $plaintext = $pcfb_enc->($plaintext);

   my $partsize = $padded_len < 16384      ? $padded_len
                : $padded_len < 16384 << 7 ? 16384
                :                            $padded_len >> 7; # 2MB

   my $dig = "";
   for (my $ofs = ($padded_len-1) - ($padded_len-1) % $partsize; $ofs >= 0; $ofs -= $partsize) {
      $dig = Digest::SHA1::sha1 substr ($plaintext, $ofs, $partsize) . $dig;
   }

   my $sini = unpack "H*", $dig;

   my $route = sprintf
           "Document-header\xfe%s\xff"
         . "Initial-digest\xfe%s\xff"
         . "Part-size\xfe%x\xff"
         . "Symmetric-cipher\xfe%s\xff",
           $senc, $sini, $partsize, $cipher;

   $route = Net::FCP::Util::encode_base64 +(Digest::SHA1::sha1 $route) . (pack "C", $padded_log) . "\x03\x02";
   $hash = Net::FCP::Util::encode_base64 $hash;

   return "freenet:CHK\@$route,$hash";
   $self;
}

=item $size = $key->size

Returns the size of the data (in bytes).

=cut

=item $digest = $key->digest

Return the store digest/hash.

=cut

=item $keynum = $key->keynumber

Returns the keynumber (version?)

=cut

=item $chk = $key->chk

Return the full CHK.

=cut

=back

=head1 SEE ALSO

L<Net::FCP>.

=head1 BUGS

Not heavily tested.

=head1 AUTHOR

 Marc Lehmann <pcg@goof.com>
 http://home.schmorp.de/

=cut

1;

Revision:	1.7
Committed:	Wed Jan 12 20:37:33 2005 UTC (21 years, 8 months ago) by root
Branch:	MAIN
Changes since 1.6:	+1 -1 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3			Net::FCP::Key::CHK - manage CHK keys.
4
5			=head1 SYNOPSIS
6
7			use Net::FCP::Key::CHK;
8
9			my $key = new Net::FCP::Key::CHK;
10			my $key = new_from_uri Net::FCP::Key::CHK $uri;
11			my $key = new_from_data Net::FCP::Key::CHK $data, $metadata;
12			... more to come
13
14
15			=head1 DESCRIPTION
16
17			=head2 THE Net::FCP::Key::CHK CLASS
18
19			=over 4
20
21			=cut
22
23			package Net::FCP::Key::CHK;
24
25			use Carp;
26			use Digest::SHA1;
27	root	1.3	use MIME::Base64;
28
29			use Crypt::Rijndael;
30	root	1.2	use Crypt::Twofish;
31	root	1.1
32	root	1.2	use Net::FCP::Util;
33
34	root	1.1	no warnings;
35
36			=item my $key = new Net::FCP::Key::CHK;
37
38	root	1.5	Heavily under development, don't use :)
39	root	1.1
40			=cut
41
42			sub new {
43			my $class = shift;
44
45			bless { }, $class;
46			}
47
48	root	1.6	=item my $key = new_from_data Net::FCP::Key::CHK $metadata, $data[, $cipher];
49	root	1.1
50			Generate a CHK from the given data and metadata strings.
51
52			=cut
53
54			sub new_from_data {
55	root	1.3	my ($class, $metadata, $data, $cipher) = @_;
56	root	1.1
57	root	1.3	$class->new->set_data ($metadata, $data, $cipher);
58	root	1.2	}
59
60	root	1.3	sub rolling_hashpad($$$) {
61			my $sha1 = $_[1];
62	root	1.2	my $pad = "";
63	root	1.3	my $dig;
64	root	1.2
65	root	1.3	while ($_[2] > length $_[0]) {
66			$sha1->add ($dig = $sha1->digest_noreset);
67	root	1.2	$pad .= $dig;
68			$_[0] .= $pad;
69			}
70
71	root	1.3	substr $_[0], $_[2], length $_[0], "";
72	root	1.2	}
73
74			sub encode_number($) {
75			my $num = pack "N", $_[0];
76			$num =~ s/^\x00+//;
77			pack "n a*", length $num, $num;
78	root	1.1	}
79
80			sub set_data {
81	root	1.3	my ($self, $metadata, $data, $cipher) = @_;
82
83			$cipher \|\|= "Twofish";
84
85			my $cipher_class = "Crypt::$cipher";
86
87			$cipher_class->blocksize == 16 or die "only ciphers with a blocksize of 128 bits are supported";
88	root	1.2
89			my $total_len = (length $metadata) + (length $data);
90	root	1.3	my $padded_log = Net::FCP::Util::log2 $total_len, 10;
91			my $padded_len = 1 << $padded_log;
92	root	1.2
93			my $plaintext = "$metadata$data";
94	root	1.1
95	root	1.3	# crypto key (hash) generation. this is an iterative
96			# algorithm, but it is "unrolled" here for the
97			# common keysize of 16 bytes.
98			my $data_sha1 = Digest::SHA1->new->add ($plaintext);
99	root	1.1
100			# only works for 128 bit keys
101			my $k = new Digest::SHA1;
102			$k->add ("\x00" x 1);
103	root	1.3	$k->add ($data_sha1->clone->digest);
104	root	1.2
105	root	1.3	my $hash = substr $k->digest, 0, 16; # extract leading 128 bit
106	root	1.2
107			my $buf = "";
108
109			$buf .= pack "n a20", 20, Digest::SHA1::sha1 $hash;
110
111			$buf .= encode_number $total_len;
112			$buf .= encode_number length $metadata;
113
114			$buf .= "\x00\x00";
115
116	root	1.3	rolling_hashpad $buf, Digest::SHA1->new->add ($buf), 1 << Net::FCP::Util::log2 length $buf;
117	root	1.2
118	root	1.4	my $pcfb_cipher = $cipher_class->new ($hash);
119			my $pcfb_reg = "\x00" x 16;
120	root	1.2
121			my $pcfb_enc = sub {
122	root	1.3	my $length = length $_[0];
123	root	1.4	my $enc = "";
124	root	1.3	for (my $i = 0; $i < $length; $i += 16) {
125	root	1.4	$enc .= $pcfb_reg = $pcfb_cipher->encrypt ($pcfb_reg) ^ substr $_[0], $i, 16;
126	root	1.2	}
127	root	1.4	$enc;
128	root	1.2	};
129
130	root	1.3	# buf length must be multiple of 16
131	root	1.4	$buf = $pcfb_enc->($buf);
132	root	1.2
133			my $senc = unpack "H*", $buf;
134
135	root	1.3	rolling_hashpad $plaintext, $data_sha1, $padded_len;
136	root	1.2
137	root	1.3	# plaintext length must be a multiple of 16, too
138	root	1.4	$plaintext = $pcfb_enc->($plaintext);
139	root	1.3
140			my $partsize = $padded_len < 16384 ? $padded_len
141			: $padded_len < 16384 << 7 ? 16384
142			: $padded_len >> 7; # 2MB
143	root	1.2
144			my $dig = "";
145			for (my $ofs = ($padded_len-1) - ($padded_len-1) % $partsize; $ofs >= 0; $ofs -= $partsize) {
146			$dig = Digest::SHA1::sha1 substr ($plaintext, $ofs, $partsize) . $dig;
147			}
148
149			my $sini = unpack "H*", $dig;
150
151	root	1.3	my $route = sprintf
152	root	1.2	"Document-header\xfe%s\xff"
153			. "Initial-digest\xfe%s\xff"
154			. "Part-size\xfe%x\xff"
155			. "Symmetric-cipher\xfe%s\xff",
156	root	1.3	$senc, $sini, $partsize, $cipher;
157	root	1.2
158	root	1.3	$route = Net::FCP::Util::encode_base64 +(Digest::SHA1::sha1 $route) . (pack "C", $padded_log) . "\x03\x02";
159			$hash = Net::FCP::Util::encode_base64 $hash;
160	root	1.2
161	root	1.3	return "freenet:CHK\@$route,$hash";
162	root	1.2	$self;
163	root	1.1	}
164
165			=item $size = $key->size
166
167			Returns the size of the data (in bytes).
168
169			=cut
170
171			=item $digest = $key->digest
172
173			Return the store digest/hash.
174
175			=cut
176
177			=item $keynum = $key->keynumber
178
179			Returns the keynumber (version?)
180
181			=cut
182
183			=item $chk = $key->chk
184
185			Return the full CHK.
186
187			=cut
188
189			=back
190
191			=head1 SEE ALSO
192
193			L<Net::FCP>.
194
195			=head1 BUGS
196
197			Not heavily tested.
198
199			=head1 AUTHOR
200
201			Marc Lehmann <pcg@goof.com>
202	root	1.7	http://home.schmorp.de/
203	root	1.1
204			=cut
205
206			1;
207