#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/nistspecialpublication800-38c.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;

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