# Crypt::AuthEnc::GCM - phpMan

## NAME
    [Crypt::AuthEnc::GCM] - Authenticated encryption in GCM mode

## SYNOPSIS
     ### OO interface
     use [Crypt::AuthEnc::GCM];

     # encrypt and authenticate
     my $ae = [Crypt::AuthEnc::GCM]->new("AES", $key, $iv);
     $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');
     my $tag = $ae->encrypt_done();

     # decrypt and verify
     my $ae = [Crypt::AuthEnc::GCM]->new("AES", $key, $iv);
     $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');
     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::GCM] qw(gcm_encrypt_authenticate gcm_decrypt_verify);

     my ($ciphertext, $tag) = gcm_encrypt_authenticate('AES', $key, $iv, $adata, $plaintext);
     my $plaintext = gcm_decrypt_verify('AES', $key, $iv, $adata, $ciphertext, $tag);

## DESCRIPTION
    Galois/Counter Mode (GCM) - provides encryption and authentication.

## EXPORT
    Nothing is exported by default.

    You can export selected functions:

      use [Crypt::AuthEnc::GCM] qw(gcm_encrypt_authenticate gcm_decrypt_verify);

## FUNCTIONS
  gcm_encrypt_authenticate
     my ($ciphertext, $tag) = gcm_encrypt_authenticate($cipher, $key, $iv, $adata, $plaintext);

     # $cipher .. 'AES' or name of any other cipher with 16-byte block len
     # $key ..... AES key of proper length (128/192/256bits)
     # $iv ...... initialization vector
     # $adata ... additional authenticated data

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

## METHODS
  new
     my $ae = [Crypt::AuthEnc::GCM]->new($cipher, $key);
     #or
     my $ae = [Crypt::AuthEnc::GCM]->new($cipher, $key, $iv);

     # $cipher .. 'AES' or name of any other cipher
     # $key ..... encryption key of proper length
     # $iv ...... initialization vector (optional, you can set it later via iv_add method)

  iv_add
    Set initialization vector (IV).

     $ae->iv_add($iv_data);                        #can be called multiple times

  adata_add
    Add additional authenticated data. Can be called after all "iv_add"
    calls but before the first "encrypt_add" or "decrypt_add".

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

  encrypt_add
     $ciphertext = $ae->encrypt_add($data);        # can be called multiple times

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

  decrypt_add
     $plaintext = $ae->decrypt_add($ciphertext);   # can be called multiple times

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

  reset
     $ae->reset;

  clone
     my $ae_new = $ae->clone;

## SEE ALSO
    *   CryptX, [Crypt::AuthEnc::CCM], [Crypt::AuthEnc::EAX],
        [Crypt::AuthEnc::OCB]

    *   <<https://en.wikipedia.org/wiki/Galois/Counter_Mode>>