pykyber 0.2.0

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

# Deterministic key generation from a 64-byte seed
seed = bytes(range(64))
keypair = pykyber.Kyber768(seed=seed)

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

# Or unpack directly as tuple
public_key, secret_key = keypair   # same as above

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

# Serialization and Utilities
hex_pk = keypair.public_key_hex    # Get hex representation
b64_sk = keypair.secret_key_b64    # Get base64 representation
data = keypair.to_dict()           # Get dictionary of hex keys

# Encapsulation results also support serialization
ct_hex = result.ciphertext_hex
ss_b64 = result.shared_secret_b64

# Or unpack directly as tuple
ciphertext, shared_secret = keypair.encapsulate()   # same as above

# 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)

# Load a Keypair object from existing keys
keypair = pykyber.Kyber768.from_keys(public_key, 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	1568 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
• Invalid seed size: Seed must be exactly 64 bytes for deterministic generation

Performance

Performance benchmarks (100 iterations each):

Variant	Keypair	Encapsulate	Decapsulate
Kyber512	0.44 ms (2,262/s)	0.58 ms (1,721/s)	0.71 ms (1,404/s)
Kyber768	0.76 ms (1,312/s)	0.90 ms (1,111/s)	1.08 ms (930/s)
Kyber1024	1.08 ms (928/s)	1.35 ms (743/s)	1.55 ms (645/s)

Run benchmarks and generate graphs:

make benchmark

Generated graphs:

Performance Comparison

Operation Breakdown

Scalability

Throughput

License

MIT