mpc-secret-shares 0.2.0

MPC primitives over Shamir secret shares, implemented from the SoK paper

mpc-secret-shares

A pure-Python library for Secure Multiparty Computation (MPC) over Secret Shares.

Implements the protocols described in:

SoK: Secure Computation over Secret Shares

All protocols operate over a prime finite field Z_p using Shamir's (t,n)-secret sharing: any t out of n parties can reconstruct a secret; fewer than t parties learn nothing.

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Installation

pip install mpc-secret-shares

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Quick Start

import random
from mpc_secret_shares import share, reconstruct, secure_mult, secure_lt, is_zero

random.seed(42)

# MPC parameters
p = 11   # prime field Z_11
n = 3    # three parties
t = 2    # any 2 shares reconstruct the secret

# Share two secrets
sh_u = share(S=4, n=n, t=t, P=p)
sh_v = share(S=5, n=n, t=t, P=p)

# Secure multiplication: 4 × 5 = 20 ≡ 9 (mod 11)
sh_w = secure_mult(sh_u, sh_v, n=n, t=t, P=p)
print(f"4 × 5 mod 11 = {reconstruct(sh_w[:t], p)}")   # → 9

# Secure comparison: 4 < 5 ?
sh_cmp = secure_lt(sh_u, sh_v, n=n, t=t, p=p)
print(f"4 < 5 → {bool(reconstruct(sh_cmp[:t], p))}")  # → True

# IsZero test
sh_zero = share(S=0, n=n, t=t, P=p)
print(f"is_zero(0) = {reconstruct(is_zero(sh_zero, n=n, t=t, p=p)[:t], p)}")  # → 1

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API Reference

v0.2.0 clean names

Clean name	Description
share(S, n, t, P)	Shamir secret sharing
reconstruct(shares, p)	Lagrange interpolation
secure_mult(u, v, n, t, p)	Secure multiplication
secure_lt(u, v, n, t, p)	Secure 1_{u < v}
less_than_half_p(u, n, t, p)	Secure 1_{u < p/2}
lsb(u, n, t, p)	Secure least-significant-bit
random_bit(n, t, p)	Shared random bit
bitwise_lt(a, b_bits, n, t, p)	Bitwise comparison
is_zero(u, n, t, p)	Secure equality to zero
secure_inv(u, n, t, p)	Secure modular inverse
secure_div(u, v, u_bits, n, t, p)	Secure floor division
secure_sqrt(u, u_bits, n, t, p)	Secure integer square root
mary_or(bits, n, t, p)	Secure m-ary OR
improved_mary_or(bits, n, t, p)	Communication-efficient OR
kth_ranked(dataset, M, k)	k-th ranked element (cleartext)

Unchanged names

Name	Description
protocol_3_rng(n, t, p)	Shared random number
protocol_3_1_affine_combination(a, b, c, u, v, p)	Local α + β·u + γ·v
binary_long_division(u, v)	Cleartext binary long division
algorithm_14_bitwise_sqrt(u)	Cleartext integer square root
compute_or_polynomial_coefficients(m, p)	OR polynomial coefficients
square_and_multiply(x, c, n)	Modular exponentiation
shares_add / sub / scalar / ...	Local share arithmetic

Deprecated names (removed in v1.0)

All protocol_N_* and algorithm_N_* names that have a clean alias above still work but emit a DeprecationWarning on every call.

# Old style (works, but warns):
from mpc_secret_shares import protocol_1_share
sh = protocol_1_share(7, n=3, t=2, P=11)
# DeprecationWarning: 'protocol_1_share' is deprecated; use 'share' instead.

# New style:
from mpc_secret_shares import share
sh = share(7, n=3, t=2, P=11)

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Running the Tests

cd mpc_project
pip install pytest
pytest tests/ -v

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License

MIT — see LICENSE.