pykyber 0.1.6

Kyber post-quantum key encapsulation in Rust

PyKyber

A Python library for Kyber post-quantum key encapsulation, implemented in Rust.

Installation

pip install pykyber

Quick Start

import pykyber

# Generate a keypair (Alice)
alice_keypair = pykyber.Kyber768()

# Encapsulate - create shared secret (Bob)
bob_result = pykyber.Kyber768.encapsulate(alice_keypair.public_key)

# Decapsulate - recover shared secret (Alice)
shared_secret = alice_keypair.decapsulate(bob_result.ciphertext)

# Both parties now share the same secret
print(f"Match: {bob_result.shared_secret == shared_secret}")

API Usage

import pykyber

# Create a keypair - instant generation on class instantiation
keypair = pykyber.Kyber512()   # ~AES-128 security
keypair = pykyber.Kyber768()   # ~AES-192 security
keypair = pykyber.Kyber1024() # ~AES-256 security

# Access raw key bytes
public_key = keypair.public_key    # bytes
secret_key = keypair.secret_key    # bytes

# Encapsulate - create ciphertext and shared secret
result = keypair.encapsulate()
# result.ciphertext     - bytes to send to receiver
# result.shared_secret  - 32 bytes shared secret

# Decapsulate - recover shared secret from ciphertext
shared_secret = keypair.decapsulate(result.ciphertext)

# Static methods - use without creating a keypair instance

# Encapsulate with just a public key
result = pykyber.Kyber768.encapsulate(public_key)

# Decapsulate with just ciphertext and secret key
shared_secret = pykyber.Kyber768.decapsulate(ciphertext, secret_key)

Key Sizes

Variant	Public Key	Secret Key	Ciphertext	Shared Secret
Kyber-512	800 bytes	1632 bytes	768 bytes	32 bytes
Kyber-768	1184 bytes	2400 bytes	1088 bytes	32 bytes
Kyber-1024	1568 bytes	3168 bytes	1408 bytes	32 bytes

Error Handling

All operations raise KyberError when invalid input is provided:

import pykyber

try:
    pykyber.Kyber768.encapsulate(b"too_short")
except pykyber.KyberError as e:
    print(e)
# Output: Invalid public key for Kyber768.encapsulate: expected 1184 bytes, got 10. 
# Ensure you're using the correct Kyber variant (Kyber512=800, Kyber768=1184, Kyber1024=1568).

Common error cases:

• Invalid public key size: Wrong number of bytes for the Kyber variant
• Invalid ciphertext size: Wrong number of bytes when decapsulating
• Invalid secret key size: Wrong number of bytes for the Kyber variant

License

MIT