#NAME

Crypt::AuthEnc::OCB - Authenticated encryption in OCBv3 mode

#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);

#DESCRIPTION

This module implements OCB v3 according to https://tools.ietf.org/html/rfc7253

#EXPORT

Nothing is exported by default.

You can export selected functions:

use Crypt::AuthEnc::OCB qw(ocb_encrypt_authenticate ocb_decrypt_verify);

#FUNCTIONS

#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

#ocb_decrypt_verify

my $plaintext = ocb_decrypt_verify($cipher, $key, $nonce, $adata, $ciphertext, $tag);
# on error returns undef

#METHODS

#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

#adata_add

$ae->adata_add($adata);                        #can be called multiple times

#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)

#encrypt_last

$ciphertext = $ae->encrypt_last($data);

#encrypt_done

$tag = $ae->encrypt_done();                    # returns $tag value

#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)

#decrypt_last

$plaintext = $ae->decrypt_last($data);

#decrypt_done

my $tag = $ae->decrypt_done;           # returns $tag value
#or
my $result = $ae->decrypt_done($tag);  # returns 1 (success) or 0 (failure)

#clone

my $ae_new = $ae->clone;

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