PyQuorum

Cryptographic library for secret sharing and key management, powered by Rust

Installation

pip install pyquorum

Quick Start

from pyquorum import ShamirScheme, BlakleyScheme, AdditiveScheme, Shares, generate_key, hkdf

k = 3  # threshold for combine
n = 5  # number of total shares
key = generate_key()  # 32-byte secret

# Shamir and Blakley are threshold schemes: any k of the n shares restore the key
scheme = ShamirScheme(k, n)  # or BlakleyScheme(k, n)
shares = scheme.split(key)
assert scheme.combine(shares) == key

# Additive is n-of-n: every single share is required
additive = AdditiveScheme(n)
additive_shares = additive.split(key)
assert additive.combine(additive_shares) == key

# Derive subkeys from the secret with HKDF (RFC 5869, HMAC-SHA256)
subkey = hkdf(key, 32, salt=b"session", info=b"encryption")

# Shares can be serialized; the index stays the dictionary key
restored = Shares.from_json(shares.to_json())
assert scheme.combine(restored) == key

Security

This library does:

• generate key
• split secret
• combine secret

What it doesn't:

• replace encryption packages like cryptography, pyserpent and etc

WARNING - This library is in active development (0.x.x). It has not undergone a professional security audit and contains known vulnerabilities. Do not use in production.

You can review known vulnerabilities in SECURITY_ISSUES_TRACKER.md

If you found a security issue, please refer to SECURITY.md

Roadmap to v1.0.0

• - Shamir Scheme
• - Blakley Scheme
• - Additive Scheme
• - HKDF Key Derivation
• - Threshold ECDSA

Support

If you find this package usefull, you can star repo on github

Theory

Shamir Scheme Share

How to split a secret key

How to combine a secret key

Example

Blakley Scheme Share

How to split a secret key

How to combine a secret key

Example

Additive Scheme Share

Every share is a uniformly random byte string of the same length as the secret, and the last share is the xor of the secret with all the others. The scheme is therefore n-of-n: any n-1 shares are independent of the secret, and all n are required to restore it. Shares are combined with xor in GF(2^256), so the split is exact and needs no modular arithmetic.

scheme = AdditiveScheme(3)
shares = scheme.split(key)   # "1:<hex>", "2:<hex>", "3:<hex>"
assert scheme.combine(shares) == key

HKDF Key Derivation

hkdf(ikm, length, salt=b"", info=b"") implements HKDF (RFC 5869) with HMAC-SHA256 and matches the RFC SHA-256 test vectors. length is the number of output bytes and must be in 1..255*32; a missing or empty salt means the RFC default of HashLen zero bytes.

subkey = hkdf(key, 64, salt=b"session-1", info=b"aes-key")