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=head1 NAME |
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|
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Net::FCP::Key::CHK - manage CHK keys. |
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|
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=head1 SYNOPSIS |
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|
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use Net::FCP::Key::CHK; |
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|
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my $key = new Net::FCP::Key::CHK; |
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my $key = new_from_uri Net::FCP::Key::CHK $uri; |
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my $key = new_from_data Net::FCP::Key::CHK $data, $metadata; |
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... more to come |
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|
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|
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=head1 DESCRIPTION |
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|
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=back |
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|
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=head2 THE Net::FCP::Key::CHK CLASS |
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|
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=over 4 |
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|
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=cut |
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|
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package Net::FCP::Key::CHK; |
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|
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use Carp; |
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use Digest::SHA1; |
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use MIME::Base64; |
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|
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use Crypt::Rijndael; |
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use Crypt::Twofish; |
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|
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use Net::FCP::Util; |
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|
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no warnings; |
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|
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=item my $key = new Net::FCP::Key::CHK; |
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|
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Don't use :) |
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|
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=cut |
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|
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sub new { |
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my $class = shift; |
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|
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bless { }, $class; |
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} |
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|
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=item my $key = new_from_data Net::FCP::Key::CHK $metadata, $data, $cipher; |
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|
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Generate a CHK from the given data and metadata strings. |
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|
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=cut |
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|
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sub new_from_data { |
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my ($class, $metadata, $data, $cipher) = @_; |
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|
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$class->new->set_data ($metadata, $data, $cipher); |
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} |
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|
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sub rolling_hashpad($$$) { |
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my $sha1 = $_[1]; |
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my $pad = ""; |
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my $dig; |
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|
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while ($_[2] > length $_[0]) { |
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$sha1->add ($dig = $sha1->digest_noreset); |
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$pad .= $dig; |
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$_[0] .= $pad; |
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} |
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|
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substr $_[0], $_[2], length $_[0], ""; |
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} |
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|
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sub encode_number($) { |
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my $num = pack "N", $_[0]; |
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$num =~ s/^\x00+//; |
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pack "n a*", length $num, $num; |
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} |
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|
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sub set_data { |
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my ($self, $metadata, $data, $cipher) = @_; |
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|
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$cipher ||= "Twofish"; |
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|
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my $cipher_class = "Crypt::$cipher"; |
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|
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$cipher_class->blocksize == 16 or die "only ciphers with a blocksize of 128 bits are supported"; |
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|
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my $total_len = (length $metadata) + (length $data); |
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my $padded_log = Net::FCP::Util::log2 $total_len, 10; |
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my $padded_len = 1 << $padded_log; |
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|
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my $plaintext = "$metadata$data"; |
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|
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# crypto key (hash) generation. this is an iterative |
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# algorithm, but it is "unrolled" here for the |
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# common keysize of 16 bytes. |
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my $data_sha1 = Digest::SHA1->new->add ($plaintext); |
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|
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# only works for 128 bit keys |
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my $k = new Digest::SHA1; |
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$k->add ("\x00" x 1); |
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$k->add ($data_sha1->clone->digest); |
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|
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my $hash = substr $k->digest, 0, 16; # extract leading 128 bit |
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|
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my $buf = ""; |
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|
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$buf .= pack "n a20", 20, Digest::SHA1::sha1 $hash; |
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|
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$buf .= encode_number $total_len; |
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$buf .= encode_number length $metadata; |
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|
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$buf .= "\x00\x00"; |
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|
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rolling_hashpad $buf, Digest::SHA1->new->add ($buf), 1 << Net::FCP::Util::log2 length $buf; |
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|
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my $pcfbc = $cipher_class->new ($hash); |
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my $pcfbr = "\x00" x 16; |
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my $pcfb = 16; |
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|
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my $pcfb_enc = sub { |
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my $length = length $_[0]; |
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for (my $i = 0; $i < $length; $i += 16) { |
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substr $_[0], $i, 16, $pcfbr = $pcfbc->encrypt ($pcfbr) ^ substr $_[0], $i, 16; |
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} |
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}; |
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|
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# buf length must be multiple of 16 |
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$pcfb_enc->($buf); |
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|
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my $senc = unpack "H*", $buf; |
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|
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rolling_hashpad $plaintext, $data_sha1, $padded_len; |
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|
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# plaintext length must be a multiple of 16, too |
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print "<"; |
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$pcfb_enc->($plaintext); |
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print ">"; |
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|
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my $partsize = $padded_len < 16384 ? $padded_len |
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: $padded_len < 16384 << 7 ? 16384 |
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: $padded_len >> 7; # 2MB |
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|
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my $dig = ""; |
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for (my $ofs = ($padded_len-1) - ($padded_len-1) % $partsize; $ofs >= 0; $ofs -= $partsize) { |
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$dig = Digest::SHA1::sha1 substr ($plaintext, $ofs, $partsize) . $dig; |
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} |
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|
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my $sini = unpack "H*", $dig; |
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|
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my $route = sprintf |
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"Document-header\xfe%s\xff" |
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. "Initial-digest\xfe%s\xff" |
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. "Part-size\xfe%x\xff" |
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. "Symmetric-cipher\xfe%s\xff", |
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$senc, $sini, $partsize, $cipher; |
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|
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$route = Net::FCP::Util::encode_base64 +(Digest::SHA1::sha1 $route) . (pack "C", $padded_log) . "\x03\x02"; |
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$hash = Net::FCP::Util::encode_base64 $hash; |
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|
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return "freenet:CHK\@$route,$hash"; |
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$self; |
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} |
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|
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=item $size = $key->size |
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|
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Returns the size of the data (in bytes). |
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|
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=cut |
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|
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=item $digest = $key->digest |
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|
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Return the store digest/hash. |
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|
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=cut |
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|
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=item $keynum = $key->keynumber |
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|
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Returns the keynumber (version?) |
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|
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=cut |
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|
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=item $chk = $key->chk |
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|
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Return the full CHK. |
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|
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=cut |
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|
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=back |
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|
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=head1 SEE ALSO |
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|
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L<Net::FCP>. |
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|
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=head1 BUGS |
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|
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Not heavily tested. |
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|
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=head1 AUTHOR |
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|
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Marc Lehmann <pcg@goof.com> |
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http://www.goof.com/pcg/marc/ |
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|
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=cut |
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|
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if (0) { |
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my $data = do { local $/; <> }; |
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my $metadata = substr $data, 0, 0x3f, ""; |
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$metadata = "x" x 3000; |
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$data = "a" x 4098; |
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|
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warn Net::FCP::Key::CHK->new_from_data ($metadata, $data); |
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use Net::FCP; my $fcp = new Net::FCP; warn $fcp->generate_chk ($metadata, $data); |
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} else { |
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use Net::FCP; |
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my $fcp = new Net::FCP; |
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|
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$|=1; |
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use Time::HiRes 'time'; |
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while () { |
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my $meta = join "", map chr(rand(256)), 1..(30+rand(20)); |
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my $data = join "", map chr(rand(256)), 1..(20+rand(200000)); |
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my $meta = join "", map chr(rand(256)), 1..1024; |
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my $data = join "", map chr(rand(256)), 1..1024000; |
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printf "%d - %d ", length $meta, length $data; |
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my $t1 = time; |
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my $b = $fcp->generate_chk ($meta, $data, "Rijndael"); |
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my $t2 = time; |
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my $a = Net::FCP::Key::CHK->new_from_data ($meta, $data, "Rijndael"); |
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my $t3 = time; |
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printf "%.2f %.2f ", $t2-$t1, $t3-$t2; |
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die "$a ne $b" unless "$a" eq $b; |
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print "ok\n"; |
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} |
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} |
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|
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1; |
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|
