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;

SEE ALSO

       •   CryptX, Crypt::AuthEnc::CCM, Crypt::AuthEnc::GCM, Crypt::AuthEnc::EAX

       •   <https://en.wikipedia.org/wiki/OCB_mode>

       •   <https://tools.ietf.org/html/rfc7253>