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ARIA

Algorithm​

ARIA (block cipher specified in KS X 1213 and related profiles) operates on 128-bit blocks with 128-, 192-, or 256-bit keys. In NoxTLS, AriaCipher::new expands the key once into round keys; encrypt_block and decrypt_block run one 16-byte block at a time and return Result so callers can handle rare internal failures consistently.

Round counts follow the standard: 12 rounds for 128-bit keys, 14 for 192-bit, 16 for 256-bit. Modes (CBC, CTR, CFB, OFB) combine these primitives with IVs or counters; they are documented on the per-mode pages below.

Purpose​

This page is the hub for ARIA in noxtls-crypto: build an AriaCipher, then call the mode helpers that take &AriaCipher. Use ARIA when a Korean or regional standard names it explicitly; where the protocol allows a modern default, AEAD (for example AES-GCM or ChaCha20-Poly1305) is usually simpler for integrity.

Mode pages

Rust API​

  • Crate: noxtls-crypto
  • Module path (conceptual): noxtls_crypto::sym (re-exported at crate root)
  • Primary symbols:
    • AriaCipher
    • AriaCipher::encrypt_block / AriaCipher::decrypt_block
    • Mode entry points (see mode pages above)

Functions and types:

  • AriaCipher::new(key) -> Result<AriaCipher> - Parameters: key is 16, 24, or 32 bytes. Behavior: runs the ARIA key schedule. Returns: AriaCipher on success, or InvalidLength if the key size is not supported.
  • Block primitives - encrypt_block(&self, block: &mut [u8; 16]) -> Result<()> and decrypt_block mutate one block in place; used internally by modes and available for custom constructions.
  • Mode helpers - Take &AriaCipher plus a 16-byte IV or initial counter (per mode); CBC requires block-aligned buffers with no automatic padding. See each linked mode page for signatures and Result / Vec return types.

Feature flags and policy​

CBC, CTR, CFB, and OFB are in the default noxtls-crypto build. ARIA-ECB is exported only with hazardous-legacy-crypto.

Examples​

use noxtls_crypto::{AriaCipher, noxtls_aria_ctr_apply};

let key = [0x10u8; 16];
let cipher = AriaCipher::new(&key)?;
let nonce_counter = [0u8; 16];
let plaintext = b"aria-stream-data";
let ciphertext = noxtls_aria_ctr_apply(&cipher, &nonce_counter, plaintext);
let recovered = noxtls_aria_ctr_apply(&cipher, &nonce_counter, &ciphertext);
assert_eq!(recovered, plaintext);
# Ok::<(), noxtls_core::Error>(())

Security and compatibility​

Treat IVs, nonces, and counters like any other stream or CBC mode: avoid reuse under the same key unless the standard defines a safe construction. Non-AEAD modes do not authenticate ciphertext; combine with a MAC or use AEAD where the protocol permits.