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;