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AES

Algorithm​

AES (Rijndael, FIPS 197) is a symmetric block cipher with 128-bit blocks and 128-, 192-, or 256-bit keys. NoxTLS expands the key once into an AesCipher value, then applies mode functions for CBC, CTR, GCM, CCM, CFB, OFB, and XTS.

Purpose​

Use AesCipher with mode helpers (aes_cbc_*, aes_gcm_*, …) exported from noxtls-crypto.

Rust API​

  • Crate: noxtls-crypto
  • Module path (conceptual): noxtls_crypto::sym (re-exported at crate root)
  • Primary symbols:
    • AesCipher
    • noxtls_aes_cbc_encrypt
    • noxtls_aes_gcm_encrypt
    • noxtls_aes_ctr_apply

Functions and types:

  • AesCipher::new(key) - Parameters: key is AES key material of length 16, 24, or 32 bytes. Behavior: expands round keys and initializes an AesCipher context reused by mode helpers. Returns: initialized AesCipher wrapped in Result.
  • Mode functions — Take &AesCipher plus mode-specific IV/nonce/AAD; see each mode page.

Feature flags and policy​

Standard noxtls-crypto build (ECB requires hazardous-legacy-crypto).

Examples​

use noxtls_crypto::AesCipher;

let key = [0x01u8; 32];
let cipher = AesCipher::new(&key)?;
let _ = cipher; // use with noxtls_aes_gcm_encrypt, noxtls_aes_cbc_encrypt, …
# Ok::<(), noxtls_core::Error>(())

Security and compatibility​

Never reuse a nonce with the same AES key in GCM or CCM; prefer random IVs from a DRBG.