# Crypt::AuthEnc::OCB - phpMan

## 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>>