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=head1 NAME |
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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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=head2 THE Net::FCP::Key::CHK CLASS |
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|
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=over 4 |
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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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Heavily under development, 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 $pcfb_cipher = $cipher_class->new ($hash); |
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my $pcfb_reg = "\x00" x 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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my $enc = ""; |
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for (my $i = 0; $i < $length; $i += 16) { |
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$enc .= $pcfb_reg = $pcfb_cipher->encrypt ($pcfb_reg) ^ substr $_[0], $i, 16; |
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} |
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$enc; |
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}; |
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|
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# buf length must be multiple of 16 |
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$buf = $pcfb_enc->($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, $padded_len; |
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|
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# plaintext length must be a multiple of 16, too |
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$plaintext = $pcfb_enc->($plaintext); |
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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 <schmorp@schmorp.de> |
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http://home.schmorp.de/ |
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|
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=cut |
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|
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1; |
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