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database/perl/vendor/lib/Crypt/OpenPGP/CFB.pm

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+# This code based slightly on the Systemics Crypt::CFB.
+# Parts Copyright (C) 1995, 1996 Systemics Ltd (http://www.systemics.com/)
+# All rights reserved.
+
+package Crypt::OpenPGP::CFB;
+use strict;
+
+sub new {
+    my $class = shift;
+    my $c = bless { }, $class;
+    $c->init(@_);
+}
+
+sub init {
+    my $c = shift;
+    my($cipher, $iv) = @_;
+    $c->{cipher} = $cipher;
+    $c->{blocksize} = $cipher->blocksize;
+    $c->{iv} = $iv || "\0" x $c->{blocksize};
+    $c;
+}
+
+sub sync { $_[0]->{unused} = '' }
+
+sub encrypt {
+    my $c = shift;
+    my($data) = @_;
+    my $ret = '';
+    my $iv = $c->{iv};
+    my $out = $c->{unused} || '';
+    my $size = length $out;
+    while ( $data ne '' ) {
+        unless ($size) {
+            $out = $c->{cipher}->encrypt($iv);
+            $size = $c->{blocksize};
+        }
+        my $in = substr $data, 0, $size, '';
+        $size -= (my $got = length $in);
+        $iv .= ($in ^= substr $out, 0, $got, '');
+        substr $iv, 0, $got, '';
+        $ret .= $in;
+    }
+    $c->{unused} = $out;
+    $c->{iv} = $iv;
+    $ret;
+}
+
+sub decrypt {
+    my $c = shift;
+    my($data) = @_;
+    my $ret = '';
+    my $iv = $c->{iv};
+    my $out = $c->{unused} || '';
+    my $size = length $out;
+    while ( $data ne '' ) {
+        unless ($size) {
+            $out = $c->{cipher}->encrypt($iv);
+            $size = $c->{blocksize};
+        }
+        my $in = substr $data, 0, $size, '';
+        $size -= (my $got = length $in);
+        substr $iv .= $in, 0, $got, '';
+        $ret .= ($in ^= substr $out, 0, $got, '');
+    }
+    $c->{unused} = $out;
+    $c->{iv} = $iv;
+    $ret;
+}
+
+1;
+__END__
+
+=head1 NAME
+
+Crypt::OpenPGP::CFB - PGP Cipher Feedback Mode
+
+=head1 SYNOPSIS
+
+    use Crypt::OpenPGP::CFB;
+
+    my $key = 'foo bar';
+    my $cipher = Crypt::Blowfish->new( $key );   # for example
+    my $cfb = Crypt::OpenPGP::CFB->new( $cipher );
+
+    my $plaintext = 'this is secret!';
+    my $ct = $cfb->encrypt( $plaintext );
+
+    my $pt = $cfb->decrypt( $ct );
+
+=head1 DESCRIPTION
+
+I<Crypt::OpenPGP::CFB> implements the variant of Cipher Feedback mode
+that PGP uses in its encryption and decryption. The key difference
+with PGP CFB is that the CFB state is resynchronized at each
+encryption/decryption. This applies both when encrypting secret key
+data and in symmetric encryption of standard encrypted data. More
+differences are described in the OpenPGP RFC, in section 13.9
+(OpenPGP CFB mode).
+
+Typically you should never need to directly use I<Crypt::OpenPGP::CFB>;
+I<Crypt::OpenPGP::Cipher> objects wrap around an instance of this
+class and provide a uniform interface to symmetric ciphers. See
+the documentation for that module for usage details.
+
+=head1 AUTHOR & COPYRIGHTS
+
+Please see the Crypt::OpenPGP manpage for author, copyright, and
+license information.
+
+=cut