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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 Crypt::Twofish; |
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use MIME::Base64; |
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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, $data; |
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|
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Generate a CHK from the given data and metadata strings. |
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|
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=cut |
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|
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sub new_from_data { |
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my ($class, $metadata, $data) = @_; |
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|
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$class->new->set_data ($metadata, $data); |
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} |
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|
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sub rolling_hashpad($$) { |
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my $d = Digest::SHA1->new->add ($_[0]); |
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my $pad = ""; |
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|
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while ($_[1] > length $_[0]) { |
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my $dig = $d->digest_noreset; |
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$d->add ($dig); |
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$pad .= $dig; |
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$_[0] .= $pad; |
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} |
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|
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substr $_[0], $_[1], 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) = @_; |
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|
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my $total_len = (length $metadata) + (length $data); |
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my $padded_len = 1 << Net::FCP::Util::log2 $total_len, 10; |
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|
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my $plaintext = "$metadata$data"; |
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|
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my $d = new Digest::SHA1; |
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$d->add ($plaintext); |
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$d = $d->digest; |
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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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$k->add ($d); |
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|
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my $hash = substr +(my $x=$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, 1 << Net::FCP::Util::log2 length $buf; |
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|
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my $pcfbc = new Crypt::Twofish $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 $pcfb_enc = sub { |
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if ($pcfb == 16) { |
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$pcfb = 0; |
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$pcfbr = $pcfbc->encrypt ($pcfbr); |
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} |
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(substr $pcfbr, $pcfb++, 1) ^= $_[0]; |
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}; |
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|
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$buf = join "", map $pcfb_enc->($_), split //, $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, $padded_len; |
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|
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$plaintext = join "", map $pcfb_enc->($_), split //, $plaintext; |
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|
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my $partsize = $padded_len > 16384 ? $padded_len >> 7 : $padded_len; |
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$partsize = 16384 if $partsize < 16384; # up to 4MB |
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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 $s = sprintf |
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"Document-header\xfe%s\xff" |
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. "Initial-digest\xfe%s\xff" |
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. "Part-size\xfe%x\xff" |
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. "Symmetric-cipher\xfe%s\xff", |
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$senc, $sini, $partsize, "Twofish"; |
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|
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warn "$s\n"; |
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|
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$s = Net::FCP::Util::encode_base64 +(Digest::SHA1::sha1 $s) . (pack "C", Net::FCP::Util::log2 $padded_len) . "\x03\x02"; |
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print "$s\n"; |
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|
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|
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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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my $data = do { local $/; <> }; |
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my $metadata = substr $data, 0, 0x3f, ""; |
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#my $metadata = substr $data, 0, 0x28, ""; |
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|
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my $key = Net::FCP::Key::CHK->new_from_data ($metadata, $data); |
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#use Net::FCP; my $fcp = new Net::FCP; warn $fcp->generate_chk ($metadata, $data); |
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|
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1; |
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