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'); $ae_dec->decrypt_done($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 o CryptX, Crypt::AuthEnc::EAX, Crypt::AuthEnc::GCM, Crypt::AuthEnc::OCB o perl v5.42.2 2026-08-10 Crypt::AuthEnc::CCM(3)