--- name: "Crypt::AuthEnc::CCM" section: "3pm" platform: "linux" package: "perl-cryptx" version: "0.091-2" release: "Arch Linux 2026-11-01" platforms: ["linux"] url: "https://new.carta.tech/Crypt::AuthEnc::CCM" --- # Crypt::AuthEnc::CCM(3pm) Authenticated encryption in CCM mode ## 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'); $ae_dec->decrypt_done($expected_tag) or die "decrypt failed"; # constant-time tag check #or, if you need the computed tag, compare it with slow_eq from Crypt::Misc #(Perl's 'eq' is not constant-time and leaks timing information) my $computed_tag = $ae_dec->decrypt_done(); die "decrypt failed" unless Crypt::Misc::slow_eq($computed_tag, $expected_tag); ### 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 is treated the same as C<''>) # $tag_len . [integer] required length of output tag ``` CCM parameters should follow \ ``` # tag length: 4, 6, 8, 10, 12, 14, 16 (reasonable minimum is 8) # nonce length: 7, 8, 9, 10, 11, 12, 13 (if you are not sure, use 11) # BEWARE nonce length determines max. enc/dec data size: max_data_size = 2^(8*(15-nonce_len)) ``` The functional helper normalizes out-of-range `$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 - • CryptX, Crypt::AuthEnc::EAX, Crypt::AuthEnc::GCM, Crypt::AuthEnc::OCB - • \