API cleanup for simplified update/final. Returns bytearrays when into is not used. Allows into buffers larger than needed. Misc other changes.
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# pyaegis
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[](https://badge.fury.io/py/pyaegis)
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[](https://github.com/LeoVasanko/pyaegis/blob/main/libaegis/LICENSE)
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Python bindings for libaegis - high-performance AEGIS authenticated encryption.
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## Overview
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pyaegis provides Python bindings to the AEGIS family of authenticated encryption algorithms implemented in the libaegis C library.
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AEGIS is a high-performance authenticated cipher that provides both confidentiality and authenticity guarantees.
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### Variant selection
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The following submodules are available:
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- **aegis128l**: 16-byte key, 16-byte nonce
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- **aegis256**: 32-byte key, 32-byte nonce
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- **aegis128x2**: 16-byte key, 16-byte nonce (recommended on most platforms)
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- **aegis128x4**: 16-byte key, 16-byte nonce (recommended on high-end Intel CPUs)
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- **aegis256x2**: 32-byte key, 32-byte nonce
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- **aegis256x4**: 32-byte key, 32-byte nonce (recommended if a 256-bit nonce is required)
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```python
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from pyaegis import aegis128x4
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```
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### One-shot Functions
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- `encrypt(key, nonce, message, ad=None, maclen=16)` - Encrypt with attached MAC
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- `decrypt(key, nonce, ciphertext, ad=None, maclen=16)` - Decrypt with attached MAC
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- `encrypt_detached(key, nonce, message, ad=None, maclen=16)` - Encrypt with detached MAC
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- `decrypt_detached(key, nonce, ciphertext, mac, ad=None, maclen=16)` - Decrypt with detached MAC
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- `stream(key, nonce, length)` - Generate pseudo-random bytes
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- `encrypt_unauthenticated(key, nonce, message)` - Encrypt without authentication (insecure)
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- `decrypt_unauthenticated(key, nonce, ciphertext)` - Decrypt without authentication (insecure)
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**Note**: Functions that return buffers (like `encrypt`, `decrypt`, `stream`) return `memoryview` objects. Callers can optionally supply their own buffer via the `into=` keyword argument to avoid memory allocations.
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### Incremental Classes
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- `Encryptor(key, nonce, ad=None)` - For streaming encryption
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- `Decryptor(key, nonce, ad=None)` - For streaming decryption
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## Installation
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### From PyPI
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Using [uv](https://docs.astral.sh/uv/):
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```bash
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uv pip install pyaegis
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```
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Or using pip:
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```bash
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pip install pyaegis
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```
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### From Source
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The package compiles the C library automatically using any installed C compiler:
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```bash
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# Clone the repository
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git clone https://github.com/LeoVasanko/pyaegis.git
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cd pyaegis
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# Install with uv (compiles C sources automatically)
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uv pip install .
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# Or for development
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uv pip install -e .
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```
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Alternatively with pip:
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```bash
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pip install .
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# Or for development
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pip install -e .
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```
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### Building a Distribution
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```bash
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# With uv
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uv run python -m build
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# Or with pip
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python -m build
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```
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This creates both source and wheel distributions in the `dist/` directory. The C sources are bundled in the package and compiled during installation.
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## Usage
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All modules (`aegis128l`, `aegis256`, `aegis128x2`, `aegis128x4`, `aegis256x2`, `aegis256x4`) provide the exact same API.
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### Basic Encryption/Decryption
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```python
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import pyaegis.aegis128l as a
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key = b"K" * a.KEYBYTES # 16 bytes for aegis128l
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nonce = b"N" * a.NPUBBYTES # 16 bytes for aegis128l
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plaintext = b"Hello, World!"
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ciphertext = a.encrypt(key, nonce, plaintext)
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decrypted = a.decrypt(key, nonce, ciphertext)
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assert decrypted == plaintext
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```
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### With Additional Authenticated Data (AAD)
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```python
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ciphertext = a.encrypt(key, nonce, plaintext, ad=b"metadata")
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plaintext = a.decrypt(key, nonce, ciphertext, ad=b"metadata")
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```
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### Detached Tag Mode
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```python
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ciphertext, mac = a.encrypt_detached(key, nonce, b"secret")
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plaintext = a.decrypt_detached(key, nonce, ciphertext, mac)
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```
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### Custom MAC Length
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Use 16 or 32-byte MACs (default 16):
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```python
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ciphertext, mac = a.encrypt_detached(key, nonce, message, maclen=32)
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plaintext = a.decrypt_detached(key, nonce, ciphertext, mac, maclen=32)
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```
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### In-Place Operations
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```python
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buffer = bytearray(b"secret message")
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mac = a.encrypt_unauthenticated_into(key, nonce, buffer)
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# buffer now contains ciphertext
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a.decrypt_unauthenticated_into(key, nonce, buffer, mac)
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# buffer now contains plaintext again
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```
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### Using Pre-allocated Buffers
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```python
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# Pre-allocate output buffer
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output = bytearray(len(plaintext) + 16) # +16 for MAC
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result = a.encrypt(key, nonce, plaintext, into=output)
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# result is a memoryview of the output buffer
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```
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### Stream Generation
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Generate pseudo-random bytes:
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```python
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random_bytes = a.stream(key, nonce, 1024)
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```
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### Incremental Encryption
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```python
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encryptor = a.Encryptor(key, nonce, ad=b"header")
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ciphertext1 = encryptor.update(b"chunk1")
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ciphertext2 = encryptor.update(b"chunk2")
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final_bytes = encryptor.final() # includes MAC
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```
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## Performance
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The library automatically detects CPU features at runtime and uses the most optimized implementation available:
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- AES-NI on Intel/AMD processors
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- ARM Crypto Extensions on ARM processors
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- AVX2 and AVX-512 for multi-lane variants
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- Software fallback for other platforms
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Multi-lane variants (X2, X4) provide higher throughput on systems with appropriate SIMD support.
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See `examples/benchmark.py` for performance measurements.
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## Error Handling
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Functions that can fail raise `ValueError` with descriptive messages:
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```python
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import pyaegis.aegis128l as a
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key = b"K" * a.KEYBYTES
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nonce = b"N" * a.NPUBBYTES
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try:
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# This will raise ValueError if authentication fails
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plaintext = a.decrypt(key, nonce, tampered_ciphertext)
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except ValueError as e:
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print(f"Decryption failed: {e}")
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```
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## Performance
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The library automatically detects CPU features at runtime and uses the most optimized implementation available:
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- AES-NI on Intel/AMD processors
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- ARM Crypto Extensions on ARM processors
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- AVX2 and AVX-512 for multi-lane variants
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- Software fallback for other platforms
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Multi-lane variants (X2, X4) provide higher throughput on systems with appropriate SIMD support.
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## Security Considerations
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- **Nonce Uniqueness**: Never reuse a nonce with the same key. If you can't maintain a counter, generate random nonces for each message.
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- **Key Management**: Generate cryptographically secure keys. Keep keys secret.
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- **AAD**: Additional authenticated data is not encrypted but is protected against tampering.
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- **MAC vs AEAD**: Use AEAD for encryption needs. MAC-only variants are for authentication without confidentiality.
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