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package Crypt::AuthEnc::OCB;
use strict;
use warnings;
our $VERSION = '0.069';
require Exporter; our @ISA = qw(Exporter); ### use Exporter 5.57 'import';
our %EXPORT_TAGS = ( all => [qw( ocb_encrypt_authenticate ocb_decrypt_verify )] );
our @EXPORT_OK = ( @{ $EXPORT_TAGS{'all'} } );
our @EXPORT = qw();
use Carp;
$Carp::Internal{(__PACKAGE__)}++;
use CryptX;
# obsolete, only for backwards compatibility
sub aad_add { goto &adata_add }
sub blocksize { return 16 }
sub CLONE_SKIP { 1 } # prevent cloning
1;
=pod
=head1 NAME
Crypt::AuthEnc::OCB - Authenticated encryption in OCBv3 mode
=head1 SYNOPSIS
### OO interface
use Crypt::AuthEnc::OCB;
# encrypt and authenticate
my $ae = Crypt::AuthEnc::OCB->new("AES", $key, $nonce, $tag_len);
$ae->adata_add('additional_authenticated_data1');
$ae->adata_add('additional_authenticated_data2');
my $ct = $ae->encrypt_add('data1');
$ct .= $ae->encrypt_add('data2');
$ct .= $ae->encrypt_add('data3');
$ct .= $ae->encrypt_last('rest of data');
my $tag = $ae->encrypt_done();
# decrypt and verify
my $ae = Crypt::AuthEnc::OCB->new("AES", $key, $nonce, $tag_len);
$ae->adata_add('additional_authenticated_data1');
$ae->adata_add('additional_authenticated_data2');
my $pt = $ae->decrypt_add('ciphertext1');
$pt .= $ae->decrypt_add('ciphertext2');
$pt .= $ae->decrypt_add('ciphertext3');
$pt .= $ae->decrypt_last('rest of data');
my $tag = $ae->decrypt_done();
die "decrypt failed" unless $tag eq $expected_tag;
#or
my $result = $ae->decrypt_done($expected_tag); # 0 or 1
### functional interface
use Crypt::AuthEnc::OCB qw(ocb_encrypt_authenticate ocb_decrypt_verify);
my ($ciphertext, $tag) = ocb_encrypt_authenticate('AES', $key, $nonce, $adata, $tag_len, $plaintext);
my $plaintext = ocb_decrypt_verify('AES', $key, $nonce, $adata, $ciphertext, $tag);
=head1 DESCRIPTION
This module implements OCB v3 according to L<https://tools.ietf.org/html/rfc7253>
=head1 EXPORT
Nothing is exported by default.
You can export selected functions:
use Crypt::AuthEnc::OCB qw(ocb_encrypt_authenticate ocb_decrypt_verify);
=head1 FUNCTIONS
=head2 ocb_encrypt_authenticate
my ($ciphertext, $tag) = ocb_encrypt_authenticate($cipher, $key, $nonce, $adata, $tag_len, $plaintext);
# $cipher .. 'AES' or name of any other cipher with 16-byte block len
# $key ..... AES key of proper length (128/192/256bits)
# $nonce ... unique nonce/salt (no need to keep it secret)
# $adata ... additional authenticated data
# $tag_len . required length of output tag
=head2 ocb_decrypt_verify
my $plaintext = ocb_decrypt_verify($cipher, $key, $nonce, $adata, $ciphertext, $tag);
# on error returns undef
=head1 METHODS
=head2 new
my $ae = Crypt::AuthEnc::OCB->new($cipher, $key, $nonce, $tag_len);
# $cipher .. 'AES' or name of any other cipher with 16-byte block len
# $key ..... AES key of proper length (128/192/256bits)
# $nonce ... unique nonce/salt (no need to keep it secret)
# $tag_len . required length of output tag
=head2 adata_add
$ae->adata_add($adata); #can be called multiple times
=head2 encrypt_add
$ciphertext = $ae->encrypt_add($data); # can be called multiple times
#BEWARE: size of $data has to be multiple of blocklen (16 for AES)
=head2 encrypt_last
$ciphertext = $ae->encrypt_last($data);
=head2 encrypt_done
$tag = $ae->encrypt_done(); # returns $tag value
=head2 decrypt_add
$plaintext = $ae->decrypt_add($ciphertext); # can be called multiple times
#BEWARE: size of $ciphertext has to be multiple of blocklen (16 for AES)
=head2 decrypt_last
$plaintext = $ae->decrypt_last($data);
=head2 decrypt_done
my $tag = $ae->decrypt_done; # returns $tag value
#or
my $result = $ae->decrypt_done($tag); # returns 1 (success) or 0 (failure)
=head2 clone
my $ae_new = $ae->clone;
=head1 SEE ALSO
=over
=item * L<CryptX|CryptX>, L<Crypt::AuthEnc::CCM|Crypt::AuthEnc::CCM>, L<Crypt::AuthEnc::GCM|Crypt::AuthEnc::GCM>, L<Crypt::AuthEnc::EAX|Crypt::AuthEnc::EAX>
=item * L<https://en.wikipedia.org/wiki/OCB_mode>
=item * L<https://tools.ietf.org/html/rfc7253>
=back
=cut
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