Aurora-Sigma AEAD

Overview

Aurora‑Sigma is a self‑contained C implementation of an AEAD (Authenticated Encryption with Associated Data) scheme built around the custom Aurora block cipher and a polynomial‑based MAC. Key features include:

• Authenticated Encryption + AAD: Supports encryption of a plaintext plus optional Associated Data (AAD). Both ciphertext and AAD are integrity‑protected.
• Nonce‑Reuse Protection: Generates a unique 96‑bit nonce per message using a per‑key monotonic counter + random salt, preventing accidental reuse.
• Quantum‑Resistant KDF: Internal PRF‑based key derivation to transform a 256‑bit base key into a working key.
• Single‐Message Format: Outputs a single message: nonce (12) || salt (8) || ciphertext || tag (16).

What’s New

• aurora_sigma_encrypt / aurora_sigma_decrypt

  • Added const uint8_t *aad, size_t aad_len parameters.
  • Message layout changed to include an 8‑byte salt immediately after the 12‑byte nonce.

• Initialization Functions

  • Classical mode: aurora_sigma_init(&ctx, key32)
  • Quantum‑resistant mode: aurora_sigma_init_qr(&ctx, base_key32)
    • Derives a fresh 32‑byte working key via two distinct PRF calls of the AEAD MAC.

Files

• Aurora.h

  • Declares:
    • void aurora_sigma_init(AuroraSigma *ctx, const uint8_t key[32]);
    • void aurora_sigma_init_qr(AuroraSigma *ctx, const uint8_t base_key[32]);
    • int aurora_sigma_encrypt(AuroraSigma *ctx, const uint8_t key[32], const uint8_t *plaintext, size_t plaintext_len, const uint8_t *aad, size_t aad_len, uint8_t *message, size_t *message_len);
    • int aurora_sigma_decrypt(AuroraSigma *ctx, const uint8_t key[32], const uint8_t *message, size_t message_len, const uint8_t *aad, size_t aad_len, uint8_t *plaintext, size_t *plaintext_len);
  • Implements the Aurora block cipher, polynomial MAC, tweak derivation, AAD‑aware tag, nonce+salt generator, and QR KDF—all in portable C.

• main.c

  • Demonstrates:
    1. Preparing a 32‑byte base key.
    2. Initializing in QR mode via aurora_sigma_init_qr().
    3. Encrypting a plaintext (with optional AAD) into nonce||salt||ct||tag.
    4. Decrypting back to recover the original message.

Usage

1. Clone the repo

   git clone https://github.com/SafeGuard-Protection/aurora-sigma-aead.git
   cd aurora-sigma-aead

2. Compile with a C compiler

   gcc -std=c11 -O2 -o aurora_demo main.c

3. Run the demo

   ./aurora_demo

   You should see:

   Decrypted: Hello, world!
   

Security Notes

• This is a proof‑of‑concept. The Aurora cipher has not undergone formal cryptanalysis. I am not responsible if the Chinese miltary uses this and their data gets leaked to the Warthunder forums.
• The QR KDF provides a first‑line of post‑quantum resilience, but the core block cipher remains classical.

License

Provided under the MIT License—see LICENSE for details.