aegisq-pqc 1.1.0

Post-quantum cryptography engine — Hybrid ML-KEM + AES-256-GCM (FIPS 203)

AegisQ

Post-Quantum Cryptography Engine for Python

AegisQ is a hybrid cryptographic library that combines ML-KEM (FIPS 203) for quantum-resistant key encapsulation with AES-256-GCM for authenticated symmetric encryption. The cryptographic core is written in Rust for performance and security guarantees, exposed to Python via PyO3.

from aegisq import AegisCipher, SecurityLevel

cipher = AegisCipher(level=SecurityLevel.ML_KEM_768)
keypair = cipher.generate_keypair()

# Encrypt
package = cipher.encrypt(b"Secret data", keypair.public_key)

# Decrypt
plaintext = cipher.decrypt(package, keypair.secret_key)

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Features

• Quantum-safe key exchange — ML-KEM (Module Lattice-based KEM), standardized as NIST FIPS 203
• Authenticated encryption — AES-256-GCM provides confidentiality and integrity in a single operation
• Three security levels — ML-KEM-512 (NIST Level 1), ML-KEM-768 (Level 3, default), ML-KEM-1024 (Level 5)
• Rust core, Python API — Cryptographic operations run in optimized Rust; Python developers get an ergonomic 3-line API
• Constant-time operations — Timing-attack resistant via subtle::ConstantTimeEq and Barrett reduction
• Memory zeroization — All secret keys and shared secrets are securely erased after use via zeroize
• Zero-copy FFI — Data passes between Python and Rust without unnecessary copies
• GIL release — Rust crypto operations release the Python GIL via py.detach(), enabling true parallelism
• Type-safe — Full PEP 561 type stubs with IDE autocompletion support
• Python 3.11+ — Built with PyO3 abi3 stable ABI for broad compatibility (3.11 through 3.13+)
• Ephemeral sessions with forward secrecy — EphemeralSession class auto-generates keypairs and destroys secrets on close
• Async support — encrypt_async() / decrypt_async() methods for non-blocking cryptographic operations

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Installation

From source (requires Rust toolchain)

# Prerequisites: Rust (via rustup), Python >= 3.11, maturin
pip install maturin

# Clone and build
git clone <repository-url>
cd aegisq
maturin develop --release

Development build (debug, faster compilation)

maturin develop

---

Quick Start

Encrypt and Decrypt (Recommended API)

The AegisCipher class handles the entire hybrid KEM-DEM flow — ML-KEM key encapsulation followed by AES-256-GCM encryption — in a single .encrypt() call.

from aegisq import AegisCipher, SecurityLevel

# 1. Receiver generates a keypair
cipher_bob = AegisCipher(level=SecurityLevel.ML_KEM_768)
keypair = cipher_bob.generate_keypair()
# keypair.public_key  → 1184 bytes (share openly)
# keypair.secret_key  → 2400 bytes (keep private)

# 2. Sender encrypts with the receiver's public key
cipher_alice = AegisCipher(level=SecurityLevel.ML_KEM_768)
encrypted_package = cipher_alice.encrypt(
    plaintext=b"Top secret medical records",
    recipient_public_key=keypair.public_key,
)
# encrypted_package is a single bytes object:
# [ ML-KEM Capsule (1088 B) | Nonce (12 B) | Auth Tag (16 B) | Ciphertext ]

# 3. Receiver decrypts
decrypted = cipher_bob.decrypt(
    encrypted_package=encrypted_package,
    secret_key=keypair.secret_key,
)
assert decrypted == b"Top secret medical records"

Raw KEM Operations (Advanced)

The MlKem class exposes low-level ML-KEM operations for users building custom protocols:

from aegisq import MlKem, SecurityLevel

kem = MlKem(level=SecurityLevel.ML_KEM_768)
keypair = kem.generate_keypair()

# Encapsulate: produces a capsule + 32-byte shared secret
capsule, shared_secret = kem.encapsulate(keypair.public_key)

# Decapsulate: recovers the same 32-byte shared secret
recovered = kem.decapsulate(capsule, keypair.secret_key)
assert shared_secret == recovered

---

Security Levels

Level	Enum Value	NIST Level	Public Key	Secret Key	Capsule	Package Overhead
ML-KEM-512	SecurityLevel.ML_KEM_512	1	800 B	1632 B	768 B	796 B
ML-KEM-768	SecurityLevel.ML_KEM_768	3 (default)	1184 B	2400 B	1088 B	1116 B
ML-KEM-1024	SecurityLevel.ML_KEM_1024	5	1568 B	3168 B	1568 B	1596 B

Package overhead = capsule + AES nonce (12 B) + AES auth tag (16 B). The total encrypted package size is overhead + plaintext length.

---

API Reference

AegisCipher (recommended for most users)

class AegisCipher:
    def __init__(self, level: SecurityLevel = SecurityLevel.ML_KEM_768) -> None
    def generate_keypair(self) -> KeyPair
    def encrypt(self, plaintext: bytes, recipient_public_key: bytes) -> bytes
    def decrypt(self, encrypted_package: bytes, secret_key: bytes) -> bytes
    async def encrypt_async(self, plaintext: bytes, recipient_public_key: bytes) -> bytes
    async def decrypt_async(self, encrypted_package: bytes, secret_key: bytes) -> bytes

EphemeralSession (forward secrecy)

class EphemeralSession:
    def __init__(self, level: SecurityLevel = SecurityLevel.ML_KEM_768) -> None
    def public_key(self) -> bytes  # Read-only, secret key never exposed
    def encrypt(self, plaintext: bytes, recipient_public_key: bytes) -> bytes
    def decrypt(self, encrypted_package: bytes) -> bytes
    def close(self) -> None
    # Also supports context manager: `with EphemeralSession() as s: ...`

MlKem (advanced, raw KEM operations)

class MlKem:
    def __init__(self, level: SecurityLevel = SecurityLevel.ML_KEM_768) -> None
    def generate_keypair(self) -> KeyPair
    def encapsulate(self, public_key: bytes) -> tuple[bytes, bytes]
    def decapsulate(self, capsule: bytes, secret_key: bytes) -> bytes

KeyPair

class KeyPair:
    public_key: bytes   # Encryption key (share openly)
    secret_key: bytes   # Decapsulation key (keep private)
    level: SecurityLevel

Exceptions

AegisQError(Exception)                          Base exception
├── DecapsulationError(AegisQError)             ML-KEM structural error (wrong buffer size)
├── DecryptionError(AegisQError)               AES-GCM auth tag failed (tampered or wrong key)
├── InvalidParameterError(AegisQError, ValueError)  Incorrect parameter sizes
├── RngError(AegisQError)                      OS CSPRNG unavailable
└── SessionExpiredError(AegisQError)           Attempted operation on closed EphemeralSession

All exceptions can be imported from the top-level package:

from aegisq import AegisQError, DecryptionError

---

Architecture

AegisQ is structured in three hermetic layers. Each layer only depends on the one below it:

┌─────────────────────────────────────────────────────────────┐
│  Layer 3: Python API  (aegisq/)                             │
│  AegisCipher, MlKem, SecurityLevel, exception hierarchy     │
│  Type hints, docstrings, developer-facing abstractions       │
├─────────────────────────────────────────────────────────────┤
│  Layer 2: FFI Bridge  (crates/aegisq-pyo3/)                 │
│  PyO3 bindings, GIL release, zero-copy data passing          │
│  No cryptographic logic — pure translation layer             │
├─────────────────────────────────────────────────────────────┤
│  Layer 1: Rust Core   (crates/aegisq-core/)                 │
│  ML-KEM (FIPS 203), AES-256-GCM, Transit Package assembly   │
│  #![no_std] compatible, constant-time, zeroize               │
└─────────────────────────────────────────────────────────────┘

• Layer 1 implements all cryptographic math in pure Rust with no_std compatibility. It has no knowledge of Python.
• Layer 2 translates Rust types to Python types via PyO3 and releases the GIL during expensive operations.
• Layer 3 provides the ergonomic Python classes that end users interact with.

---

Development

Build

maturin develop                    # Debug build (fast compilation)
maturin develop --release          # Release build (optimized)

Test

# Rust tests (unit + integration, all crates)
cargo test --workspace

# Python tests
pytest tests/python/ -v

# Specific test suites
cargo test -p aegisq-core                     # Core crypto only
pytest tests/python/test_cipher_api.py        # AegisCipher end-to-end
pytest tests/python/test_hybrid_bindings.py   # Hybrid bridge
pytest tests/python/test_kem_bindings.py      # KEM bridge
pytest tests/python/test_kem_api.py           # MlKem API

Code Quality

cargo clippy --workspace -- -D warnings   # Rust linter (warnings are errors)
cargo fmt --all                           # Rust formatting
ruff check aegisq/                        # Python type checking

---

Security

Guarantees

Property	Mechanism
IND-CCA2 security	Implicit rejection in ML-KEM Decaps (FIPS 203 §7.3)
Quantum resistance	M-LWE hardness assumption (ML-KEM)
Data confidentiality + integrity	AES-256-GCM authenticated encryption
Timing attack immunity	subtle::ConstantTimeEq, Barrett reduction
Memory scrubbing	zeroize::Zeroize on all secrets
Nonce uniqueness	Fresh 96-bit random nonce via OsRng per encrypt call
Integer overflow protection	overflow-checks = true in release profile

Important Notes

• No forward secrecy by default. If a secret key is compromised, all payloads encrypted to that key are compromised. Mitigation: Use ephemeral keypairs — generate a new keypair per session and discard the secret key after decryption.
• ML-KEM Decaps never raises an error for invalid capsules (implicit rejection). Instead, it returns a pseudorandom key, which causes AES-GCM to fail with DecryptionError. This prevents chosen-ciphertext oracle attacks.
• AES-GCM tag failure always raises DecryptionError. Unlike ML-KEM's silent rejection, a failed auth tag means the payload was tampered with or the wrong key was used.

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Standards Compliance

Standard	Description
FIPS 203	ML-KEM — Module-Lattice-Based Key-Encapsulation Mechanism (NIST, 2024)
NIST SP 800-38D	AES-GCM — Galois/Counter Mode specification

Dependencies

Crate	Purpose
aes-gcm 0.10	AES-256-GCM authenticated encryption (no_std, hardware AES-NI)
sha3 0.10	SHAKE-128/256 and SHA3-256/512 for ML-KEM (no_std)
zeroize 1.8	Secure memory erasure of secrets
subtle 2.6	Constant-time comparisons
rand_core 0.6	OS-level CSPRNG via OsRng (no_std)
pyo3 0.28	Rust-Python FFI bindings (abi3-py311)

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For complete technical documentation including the mathematical foundation, algorithm specifications, and security model details, see DOCUMENTATION.md.