Crypt::AuthEnc::CCM(3) User Contributed Perl Documentation
NAME
Crypt::AuthEnc::CCM - Authenticated encryption in CCM mode
SYNOPSIS
### OO interface
use Crypt::AuthEnc::CCM;
my $key = '...';
my $nonce = '...';
my $adata = '...';
my $tag_len = 16;
my $pt_len = 15;
my $expected_tag = '...';
# encrypt and authenticate
my $ae_enc = Crypt::AuthEnc::CCM->new("AES", $key, $nonce, $adata, $tag_len, $pt_len);
my $ct = $ae_enc->encrypt_add('data1');
$ct .= $ae_enc->encrypt_add('data2');
$ct .= $ae_enc->encrypt_add('data3');
my $tag = $ae_enc->encrypt_done();
# decrypt and verify
my $ae_dec = Crypt::AuthEnc::CCM->new("AES", $key, $nonce, $adata, $tag_len, $pt_len);
my $pt = $ae_dec->decrypt_add('ciphertext1');
$pt .= $ae_dec->decrypt_add('ciphertext2');
$pt .= $ae_dec->decrypt_add('ciphertext3');
my $computed_tag = $ae_dec->decrypt_done();
die "decrypt failed" unless $computed_tag eq $expected_tag;
#or
my $result = $ae_dec->decrypt_done($expected_tag); # 0 or 1
### functional interface
use Crypt::AuthEnc::CCM qw(ccm_encrypt_authenticate ccm_decrypt_verify);
my $key = '...';
my $nonce = '...';
my $adata = '...';
my $plaintext = '...';
my $tag_len = 16;
my ($ciphertext, $tag) = ccm_encrypt_authenticate('AES', $key, $nonce, $adata, $tag_len, $plaintext);
my $decrypted = ccm_decrypt_verify('AES', $key, $nonce, $adata, $ciphertext, $tag);
DESCRIPTION
CCM is an encrypt+authenticate mode that is built around using AES (or
any 16-byte cipher) as a primitive. Unlike EAX and OCB mode, it is
only meant for packet mode where the length of the input is known in
advance.
Use a fresh object per message. The OO constructor requires all
per-message parameters up front: key, nonce, associated data, tag
length, and the exact total plaintext/ciphertext length that will be
processed by "encrypt_add" / "decrypt_add". If you have no associated
data in OO mode, pass ''.
When verifying, decrypt_done($expected_tag) is the safer form. The
no-argument form of "decrypt_done" only returns the computed tag. The
first "encrypt_done" / "decrypt_done" call finalizes the object. After
that, further "encrypt_add", "decrypt_add", "encrypt_done", and
"decrypt_done" calls croak.
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 .. [string] 'AES' or name of any other cipher with 16-byte block len
# $key ..... [binary string] key of proper length (e.g. 128/192/256 bits for AES)
# $nonce ... [binary string] unique nonce/salt (no need to keep it secret)
# $adata ... [binary string] additional authenticated data (C<undef> is treated the same as C<''>)
# $tag_len . [integer] required length of output tag
CCM parameters should follow
<https://csrc.nist.gov/pubs/sp/800/38/c/final>
# 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))
The functional helper normalizes out-of-range $tag_len values to 16.
ccm_decrypt_verify
my $plaintext = ccm_decrypt_verify($cipher, $key, $nonce, $adata, $ciphertext, $tag);
# on error returns undef
METHODS
Unless noted otherwise, assume $ae is an existing AEAD object created
via "new", for example:
my $ae = Crypt::AuthEnc::CCM->new($cipher, $key, $nonce, $adata, $pt_len);
new
my $ae = Crypt::AuthEnc::CCM->new($cipher, $key, $nonce, $adata, $tag_len, $pt_len);
# $cipher .. [string] 'AES' or name of any other cipher with 16-byte block len
# $key ..... [binary string] key of proper length (e.g. 128/192/256 bits for AES)
# $nonce ... [binary string] unique nonce/salt (no need to keep it secret)
# $adata ... [binary string] additional authenticated data; must be a defined string scalar, use C<''> if none
# $tag_len . [integer] tag length in bytes, validated as 1..16
# $pt_len .. [integer] exact total plaintext/ciphertext length to encrypt/decrypt; must be >= 0
encrypt_add
Returns a binary string of ciphertext (raw bytes).
my $ciphertext = $ae->encrypt_add($data); # can be called multiple times
encrypt_done
Returns the authentication tag as a binary string (raw bytes). This
call finalizes the current message.
my $tag = $ae->encrypt_done; # returns $tag value
decrypt_add
Returns a binary string of plaintext (raw bytes).
my $plaintext = $ae->decrypt_add($ciphertext); # can be called multiple times
decrypt_done
Without argument returns the computed tag as a binary string. With $tag
argument returns 1 (success) or 0 (failure). This call finalizes the
current message.
my $tag = $ae->decrypt_done; # returns $tag value
#or
my $result = $ae->decrypt_done($tag); # returns 1 (success) or 0 (failure)
Use the decrypt_done($tag) form for authentication checks. The
no-argument form only returns the computed tag.
clone
Returns a copy of the AEAD object in its current state.
my $ae_new = $ae->clone;
SEE ALSO
o CryptX(3), Crypt::AuthEnc::EAX(3), Crypt::AuthEnc::GCM(3),
Crypt::AuthEnc::OCB(3)
o <https://en.wikipedia.org/wiki/CCM_mode>
perl v5.34.3 2026-05-11 Crypt::AuthEnc::CCM(3)
cryptx 0.89.0 - Generated Mon May 11 07:38:57 CDT 2026