Crypt::...Enc::EAX(3)

🎀 NAME 🎀

okay so this is the Crypt::...Enc::EAX(3) page from User Contributed Perl Documentation, and the main character is Crypt::AuthEnc::EAX — Authenticated encryption in EAX mode. 💖

✨ SYNOPSIS ✨

bestie, there are two whole flavors here: the OO interface and the functional interface. Both are iconic:

### OO interface
use Crypt::AuthEnc::EAX;

my $key = '...';
my $nonce = '...';
my $expected_tag = '...';

# encrypt and authenticate
my $ae_enc = Crypt::AuthEnc::EAX->new("AES", $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::EAX->new("AES", $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');
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::EAX qw(eax_encrypt_authenticate eax_decrypt_verify);

my $key = '...';
my $nonce = '...';
my $adata = '...';
my $plaintext = '...';

my ($ciphertext, $tag) = eax_encrypt_authenticate('AES', $key, $nonce, $adata, $plaintext);
my $decrypted = eax_decrypt_verify('AES', $key, $nonce, $adata, $ciphertext, $tag);

🌸 DESCRIPTION 🌸

EAX is that mode that needs a cipher plus CTR and OMAC support, and it gives you encryption and authentication together. It gets initialized with a random IV that can be shared publicly, additional authenticated data that can be fixed and public, and a random secret symmetric key. 🔐

This is a stateful API, bestie. You build one message by calling, in order: new, optional extra adata_add, zero or more encrypt_add or decrypt_add calls, then encrypt_done or decrypt_done. ✨

Use a fresh object per message. The optional $adata argument to new is equivalent to adding initial AAD before processing any payload. When verifying, decrypt_done($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 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::EAX qw(eax_encrypt_authenticate eax_decrypt_verify);

🧚 FUNCTIONS 🧚

⭐ eax_encrypt_authenticate

this one hands you back both the ciphertext and the tag:

my ($ciphertext, $tag) = eax_encrypt_authenticate($cipher, $key, $nonce, $adata, $plaintext);

# $cipher .. [string] 'AES' or name of any other cipher with 16-byte block len
# $key ..... [binary string] AES key of proper length (128/192/256 bits)
# $nonce ... [binary string] unique nonce (no need to keep it secret)
# $adata ... [binary string] additional authenticated data

🦋 eax_decrypt_verify

and this one gives you the plaintext back:

my $plaintext = eax_decrypt_verify($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 $ae = Crypt::AuthEnc::EAX->new($cipher, $key, $nonce);

🎀 new

my $ae = Crypt::AuthEnc::EAX->new($cipher, $key, $nonce);
#or
my $ae = Crypt::AuthEnc::EAX->new($cipher, $key, $nonce, $adata);

# $cipher .. [string] 'AES' or name of any other cipher with 16-byte block len
# $key ..... [binary string] AES key of proper length (128/192/256 bits)
# $nonce ... [binary string] unique nonce (no need to keep it secret)
# $adata ... [binary string] additional authenticated data (optional)

🍓 adata_add

Can be called only before the first encrypt_add or decrypt_add. Returns the object itself (for chaining). 💞

$ae->adata_add($adata);                        # 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)

🌈 clone

Returns a copy of the AEAD object in its current state. twin energy, lowkey.

my $ae_new = $ae->clone;

🫶 SEE ALSO 🫶

• CryptX, Crypt::AuthEnc::CCM, Crypt::AuthEnc::GCM, Crypt::AuthEnc::OCB — the whole squad.
• the wiki vibe: <https://en.wikipedia.org/wiki/EAX_mode>
• the paper: <https://web.cs.ucdavis.edu/~rogaway/papers/eax.pdf>

---

okay bye bestie, that's the whole page — source/version says perl v5.42.0, date says 2026-05-11, and it's all for Crypt::...Enc::EAX(3). 💅✨