--- name: "Crypt::AuthEnc::ChaCha20Poly1305" 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::ChaCha20Poly1305" --- # Crypt::AuthEnc::ChaCha20Poly1305(3pm) Authenticated encryption in ChaCha20-Poly1305 mode ## NAME Crypt::AuthEnc::ChaCha20Poly1305 - Authenticated encryption in ChaCha20-Poly1305 mode ## SYNOPSIS ``` ### OO interface use Crypt::AuthEnc::ChaCha20Poly1305; my $key = '...'; my $nonce = '...'; my $expected_tag = '...'; # encrypt and authenticate my $ae_enc = Crypt::AuthEnc::ChaCha20Poly1305->new($key, $nonce); $ae_enc->adata_add('additional_authenticated_data1'); $ae_enc->adata_add('additional_authenticated_data2'); 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 $ae_dec = Crypt::AuthEnc::ChaCha20Poly1305->new($key, $nonce); $ae_dec->adata_add('additional_authenticated_data1'); $ae_dec->adata_add('additional_authenticated_data2'); 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::ChaCha20Poly1305 qw(chacha20poly1305_encrypt_authenticate chacha20poly1305_decrypt_verify); my $key = '...'; my $nonce = '...'; my $adata = '...'; my $plaintext = '...'; my ($ciphertext, $tag) = chacha20poly1305_encrypt_authenticate($key, $nonce, $adata, $plaintext); my $decrypted = chacha20poly1305_decrypt_verify($key, $nonce, $adata, $ciphertext, $tag); ``` ## DESCRIPTION Provides authenticated encryption with ChaCha20-Poly1305 as defined in RFC 7539 \. This is a stateful API. Build one message by calling, in order: `"new"` or `"set_iv"`, optional `"adata_add"`, zero or more `"encrypt_add"` or `"decrypt_add"` calls, then `"encrypt_done"` or `"decrypt_done"`. Use a fresh object per message. If you construct with `new($key)` you must call `set_iv($iv)` before adding AAD or processing plaintext/ciphertext. When verifying, `decrypt_done($expected_tag)` is the safer one-step form; `decrypt_done()` without arguments only returns the calculated tag. The first `"encrypt_done"` / `"decrypt_done"` call finalizes the object. After that, further `"set_iv"`, `"set_iv_rfc7905"`, `"adata_add"`, `"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::ChaCha20Poly1305 qw(chacha20poly1305_encrypt_authenticate chacha20poly1305_decrypt_verify); ``` ## FUNCTIONS ### chacha20poly1305\_encrypt\_authenticate ``` my ($ciphertext, $tag) = chacha20poly1305_encrypt_authenticate($key, $nonce, $adata, $plaintext); # $key ..... [binary string] key of proper length (128 or 256 bits / 16 or 32 bytes) # $nonce ... [binary string] nonce (64 or 96 bits / 8 or 12 bytes) # $adata ... [binary string] additional authenticated data (optional) ``` ### chacha20poly1305\_decrypt\_verify ``` my $plaintext = chacha20poly1305_decrypt_verify($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 $ae = Crypt::AuthEnc::ChaCha20Poly1305->new($key, $nonce); ``` ### new ``` my $ae = Crypt::AuthEnc::ChaCha20Poly1305->new($key, $nonce); #or my $ae = Crypt::AuthEnc::ChaCha20Poly1305->new($key); # $key ..... [binary string] encryption key of proper length (128 or 256 bits / 16 or 32 bytes) # $nonce ... [binary string] nonce (64 or 96 bits / 8 or 12 bytes) ``` ### adata\_add Add **additional authenticated data**. Can be called only before the first `"encrypt_add"` or `"decrypt_add"`. Returns the object itself (for chaining). ``` $ae->adata_add($aad_data); # can be called multiple times ``` ### 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) ``` ### set\_iv ``` my $ae = Crypt::AuthEnc::ChaCha20Poly1305->new($key)->set_iv($nonce); # $nonce ... [binary string] nonce (64 or 96 bits / 8 or 12 bytes) ``` Call `"set_iv"` before the first `"adata_add"`, `"encrypt_add"`, or `"decrypt_add"` for a message. ### set\_iv\_rfc7905 See RFC 7905 \. ``` my $ae = Crypt::AuthEnc::ChaCha20Poly1305->new($key)->set_iv_rfc7905($nonce, $seqnum); # $nonce ... [binary string] nonce (96 bits / 12 bytes) # $seqnum .. [integer] 64-bit integer (sequence number) ``` ### clone Returns a copy of the AEAD object in its current state. ``` my $ae_new = $ae->clone; ``` ## SEE ALSO - • CryptX, Crypt::AuthEnc::XChaCha20Poly1305, Crypt::AuthEnc::GCM, Crypt::AuthEnc::CCM, Crypt::AuthEnc::EAX, Crypt::AuthEnc::OCB - • \