# Crypt::AuthEnc::CCM - phpMan

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

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

     # encrypt and authenticate
     my $ae = [Crypt::AuthEnc::CCM]->new("AES", $key, $iv, $adata, $tag_len, $pt_len);
     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::CCM]->new("AES", $key, $iv, $adata, $tag_len, $pt_len);
     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::CCM] qw(ccm_encrypt_authenticate ccm_decrypt_verify);

     ($ciphertext, $tag) = ccm_encrypt_authenticate('AES', $key, $nonce, $adata, $tag_len, $plaintext);
     $plaintext = ccm_decrypt_verify('AES', $key, $nonce, $adata, $ciphertext, $tag);

## DESCRIPTION
    CCM is a encrypt+authenticate mode that is centered around using AES (or
    any 16-byte cipher) as a primitive. Unlike EAX and OCB mode, it is only
    meant for packet mode where the length of the input is known in advance.

## EXPORT
    Nothing is exported by default.

    You can export selected functions:

     use [Crypt::AuthEnc::CCM] qw(ccm_encrypt_authenticate ccm_decrypt_verify);

## FUNCTIONS
  ccm_encrypt_authenticate
     my ($ciphertext, $tag) = ccm_encrypt_authenticate($cipher, $key, $nonce, $adata, $tag_len, $plaintext);

     # $cipher .. 'AES' or name of any other cipher with 16-byte block len
     # $key ..... key of proper length (e.g. 128/192/256bits for AES)
     # $nonce ... unique nonce/salt (no need to keep it secret)
     # $adata ... additional authenticated data
     # $tag_len . required length of output tag

    CCM parameters should follow
    <<http://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38>
    c.pdf>

     # tag length:   4, 6, 8, 10, 12, 14, 16 (reasonable minimum is 8)
     # nonce length: 7, 8, 9, 10, 11, 12, 13 (if you are not sure, use 11)
     # BEWARE nonce length determines max. enc/dec data size: max_data_size = 2^(8*(15-nonce_len))

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

## METHODS
  new
     my $ae = [Crypt::AuthEnc::CCM]->new($cipher, $key, $nonce, $adata, $tag_len, $pt_len);

     # $cipher .. 'AES' or name of any other cipher with 16-byte block len
     # $key ..... key of proper length (e.g. 128/192/256bits for AES)
     # $nonce ... unique nonce/salt (no need to keep it secret)
     # $adata ... additional authenticated data
     # $tag_len . required length of output tag
     # $pt_len .. expected length of plaintext/ciphertext to encrypt/decrypt

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

  encrypt_done
     my $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)

  clone
     my $ae_new = $ae->clone;

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

    *   <<https://en.wikipedia.org/wiki/CCM_mode>>