NAME

Crypt::AuthEnc::XChaCha20Poly1305 - Authenticated encryption in XChaCha20-Poly1305 mode

SYNOPSIS

### OO interface
use Crypt::AuthEnc::XChaCha20Poly1305;
my $key = '...';
my $nonce = '...';
my $expected_tag = '...';
# encrypt and authenticate
my $ae_enc = Crypt::AuthEnc::XChaCha20Poly1305->new($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');
my $tag = $ae_enc->encrypt_done();
# decrypt and verify
my $ae_dec = Crypt::AuthEnc::XChaCha20Poly1305->new($key, $nonce);
$ae_dec->adata_add('additional_authenticated_data1');
my $pt = $ae_dec->decrypt_add($ct);
die "decrypt failed" unless $ae_dec->decrypt_done($tag);
### functional interface
use Crypt::AuthEnc::XChaCha20Poly1305 qw(
  xchacha20poly1305_encrypt_authenticate
  xchacha20poly1305_decrypt_verify
);
my $key = '...';
my $nonce = '...';
my $adata = '...';
my $plaintext = '...';
my ($ciphertext, $tag) = xchacha20poly1305_encrypt_authenticate($key, $nonce, $adata, $plaintext);
my $decrypted = xchacha20poly1305_decrypt_verify($key, $nonce, $adata, $ciphertext, $tag);

DESCRIPTION

Since: CryptX-0.089

Provides encryption and authentication based on XChaCha20 + Poly1305 using the extended 192-bit (24-byte) nonce variant of ChaCha20-Poly1305.

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($key) you must call set_iv($nonce) 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", "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::XChaCha20Poly1305 qw(
  xchacha20poly1305_encrypt_authenticate
  xchacha20poly1305_decrypt_verify
);

FUNCTIONS

xchacha20poly1305_encrypt_authenticate

my ($ciphertext, $tag) = xchacha20poly1305_encrypt_authenticate($key, $nonce, $adata, $plaintext);
# $key ..... [binary string] encryption key (256 bits / 32 bytes)
# $nonce ... [binary string] extended nonce (192 bits / 24 bytes)
# $adata ... [binary string] additional authenticated data (optional)

Invalid key or nonce lengths croak. String-overloaded objects are accepted for $key and $nonce.

xchacha20poly1305_decrypt_verify

my $plaintext = xchacha20poly1305_decrypt_verify($key, $nonce, $adata, $ciphertext, $tag);
# on error returns undef

Invalid key or nonce lengths croak. String-overloaded objects are accepted for $key and $nonce.

METHODS

Unless noted otherwise, assume $ae is an existing AEAD object created via "new", for example:

my $ae = Crypt::AuthEnc::XChaCha20Poly1305->new($key, $nonce);

new

my $ae = Crypt::AuthEnc::XChaCha20Poly1305->new($key, $nonce);
my $ae = Crypt::AuthEnc::XChaCha20Poly1305->new($key);
# $key ..... [binary string] encryption key (256 bits / 32 bytes)
# $nonce ... [binary string] extended nonce (192 bits / 24 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 $ae = Crypt::AuthEnc::XChaCha20Poly1305->new($key)->set_iv($nonce);
# $nonce ... [binary string] extended nonce (192 bits / 24 bytes)

Call "set_iv" before the first "adata_add", "encrypt_add", or "decrypt_add" for a message.

clone

Returns a copy of the AEAD object in its current state.

my $ae_new = $ae->clone;