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#![allow(non_snake_case)]
#![cfg_attr(feature = "docs", doc(include = "../../docs/range-proof-protocol.md"))]
extern crate alloc;
#[cfg(feature = "std")]
extern crate rand;
#[cfg(feature = "std")]
use self::rand::thread_rng;
use alloc::vec::Vec;
use core::iter;
use curve25519_dalek::ristretto::{CompressedRistretto, RistrettoPoint};
use curve25519_dalek::scalar::Scalar;
use merlin::Transcript;
use crate::errors::ProofError;
use crate::generators::{BulletproofGens, PedersenGens};
use crate::inner_product_proof::InnerProductProof;
use crate::transcript::TranscriptProtocol;
use crate::util;
use rand_core::{CryptoRng, RngCore};
use serde::de::Visitor;
use serde::{self, Deserialize, Deserializer, Serialize, Serializer};
// Modules for MPC protocol
pub mod dealer;
pub mod messages;
pub mod party;
/// The `RangeProof` struct represents a proof that one or more values
/// are in a range.
///
/// The `RangeProof` struct contains functions for creating and
/// verifying aggregated range proofs. The single-value case is
/// implemented as a special case of aggregated range proofs.
///
/// The bitsize of the range, as well as the list of commitments to
/// the values, are not included in the proof, and must be known to
/// the verifier.
///
/// This implementation requires that both the bitsize `n` and the
/// aggregation size `m` be powers of two, so that `n = 8, 16, 32, 64`
/// and `m = 1, 2, 4, 8, 16, ...`. Note that the aggregation size is
/// not given as an explicit parameter, but is determined by the
/// number of values or commitments passed to the prover or verifier.
///
/// # Note
///
/// For proving, these functions run the multiparty aggregation
/// protocol locally. That API is exposed in the [`aggregation`](::range_proof_mpc)
/// module and can be used to perform online aggregation between
/// parties without revealing secret values to each other.
#[derive(Clone, Debug)]
pub struct RangeProof {
/// Commitment to the bits of the value
A: CompressedRistretto,
/// Commitment to the blinding factors
S: CompressedRistretto,
/// Commitment to the \\(t_1\\) coefficient of \\( t(x) \\)
T_1: CompressedRistretto,
/// Commitment to the \\(t_2\\) coefficient of \\( t(x) \\)
T_2: CompressedRistretto,
/// Evaluation of the polynomial \\(t(x)\\) at the challenge point \\(x\\)
t_x: Scalar,
/// Blinding factor for the synthetic commitment to \\(t(x)\\)
t_x_blinding: Scalar,
/// Blinding factor for the synthetic commitment to the inner-product arguments
e_blinding: Scalar,
/// Proof data for the inner-product argument.
ipp_proof: InnerProductProof,
}
impl RangeProof {
/// Create a rangeproof for a given pair of value `v` and
/// blinding scalar `v_blinding`.
/// This is a convenience wrapper around [`RangeProof::prove_multiple`].
///
/// # Example
/// ```
/// extern crate rand;
/// use rand::thread_rng;
///
/// extern crate curve25519_dalek;
/// use curve25519_dalek::scalar::Scalar;
///
/// extern crate merlin;
/// use merlin::Transcript;
///
/// extern crate bulletproofs;
/// use bulletproofs::{BulletproofGens, PedersenGens, RangeProof};
///
/// # fn main() {
/// // Generators for Pedersen commitments. These can be selected
/// // independently of the Bulletproofs generators.
/// let pc_gens = PedersenGens::default();
///
/// // Generators for Bulletproofs, valid for proofs up to bitsize 64
/// // and aggregation size up to 1.
/// let bp_gens = BulletproofGens::new(64, 1);
///
/// // A secret value we want to prove lies in the range [0, 2^32)
/// let secret_value = 1037578891u64;
///
/// // The API takes a blinding factor for the commitment.
/// let blinding = Scalar::random(&mut thread_rng());
///
/// // The proof can be chained to an existing transcript.
/// // Here we create a transcript with a doctest domain separator.
/// let mut prover_transcript = Transcript::new(b"doctest example");
///
/// // Create a 32-bit rangeproof.
/// let (proof, committed_value) = RangeProof::prove_single(
/// &bp_gens,
/// &pc_gens,
/// &mut prover_transcript,
/// secret_value,
/// &blinding,
/// 32,
/// ).expect("A real program could handle errors");
///
/// // Verification requires a transcript with identical initial state:
/// let mut verifier_transcript = Transcript::new(b"doctest example");
/// assert!(
/// proof
/// .verify_single(&bp_gens, &pc_gens, &mut verifier_transcript, &committed_value, 32)
/// .is_ok()
/// );
/// # }
/// ```
pub fn prove_single_with_rng<T: RngCore + CryptoRng>(
bp_gens: &BulletproofGens,
pc_gens: &PedersenGens,
transcript: &mut Transcript,
v: u64,
v_blinding: &Scalar,
n: usize,
rng: &mut T,
) -> Result<(RangeProof, CompressedRistretto), ProofError> {
let (p, Vs) = RangeProof::prove_multiple_with_rng(
bp_gens,
pc_gens,
transcript,
&[v],
&[*v_blinding],
n,
rng,
)?;
Ok((p, Vs[0]))
}
/// Create a rangeproof for a given pair of value `v` and
/// blinding scalar `v_blinding`.
/// This is a convenience wrapper around [`RangeProof::prove_single_with_rng`],
/// passing in a threadsafe RNG.
#[cfg(feature = "std")]
pub fn prove_single(
bp_gens: &BulletproofGens,
pc_gens: &PedersenGens,
transcript: &mut Transcript,
v: u64,
v_blinding: &Scalar,
n: usize,
) -> Result<(RangeProof, CompressedRistretto), ProofError> {
RangeProof::prove_single_with_rng(
bp_gens,
pc_gens,
transcript,
v,
v_blinding,
n,
&mut thread_rng(),
)
}
/// Create a rangeproof for a set of values.
///
/// # Example
/// ```
/// extern crate rand;
/// use rand::thread_rng;
///
/// extern crate curve25519_dalek;
/// use curve25519_dalek::scalar::Scalar;
///
/// extern crate merlin;
/// use merlin::Transcript;
///
/// extern crate bulletproofs;
/// use bulletproofs::{BulletproofGens, PedersenGens, RangeProof};
///
/// # fn main() {
/// // Generators for Pedersen commitments. These can be selected
/// // independently of the Bulletproofs generators.
/// let pc_gens = PedersenGens::default();
///
/// // Generators for Bulletproofs, valid for proofs up to bitsize 64
/// // and aggregation size up to 16.
/// let bp_gens = BulletproofGens::new(64, 16);
///
/// // Four secret values we want to prove lie in the range [0, 2^32)
/// let secrets = [4242344947u64, 3718732727u64, 2255562556u64, 2526146994u64];
///
/// // The API takes blinding factors for the commitments.
/// let blindings: Vec<_> = (0..4).map(|_| Scalar::random(&mut thread_rng())).collect();
///
/// // The proof can be chained to an existing transcript.
/// // Here we create a transcript with a doctest domain separator.
/// let mut prover_transcript = Transcript::new(b"doctest example");
///
/// // Create an aggregated 32-bit rangeproof and corresponding commitments.
/// let (proof, commitments) = RangeProof::prove_multiple(
/// &bp_gens,
/// &pc_gens,
/// &mut prover_transcript,
/// &secrets,
/// &blindings,
/// 32,
/// ).expect("A real program could handle errors");
///
/// // Verification requires a transcript with identical initial state:
/// let mut verifier_transcript = Transcript::new(b"doctest example");
/// assert!(
/// proof
/// .verify_multiple(&bp_gens, &pc_gens, &mut verifier_transcript, &commitments, 32)
/// .is_ok()
/// );
/// # }
/// ```
pub fn prove_multiple_with_rng<T: RngCore + CryptoRng>(
bp_gens: &BulletproofGens,
pc_gens: &PedersenGens,
transcript: &mut Transcript,
values: &[u64],
blindings: &[Scalar],
n: usize,
rng: &mut T,
) -> Result<(RangeProof, Vec<CompressedRistretto>), ProofError> {
use self::dealer::*;
use self::party::*;
if values.len() != blindings.len() {
return Err(ProofError::WrongNumBlindingFactors);
}
let dealer = Dealer::new(bp_gens, pc_gens, transcript, n, values.len())?;
let parties: Vec<_> = values
.iter()
.zip(blindings.iter())
.map(|(&v, &v_blinding)| Party::new(bp_gens, pc_gens, v, v_blinding, n))
// Collect the iterator of Results into a Result<Vec>, then unwrap it
.collect::<Result<Vec<_>, _>>()?;
let (parties, bit_commitments): (Vec<_>, Vec<_>) = parties
.into_iter()
.enumerate()
.map(|(j, p)| {
p.assign_position_with_rng(j, rng)
.expect("We already checked the parameters, so this should never happen")
})
.unzip();
let value_commitments: Vec<_> = bit_commitments.iter().map(|c| c.V_j).collect();
let (dealer, bit_challenge) = dealer.receive_bit_commitments(bit_commitments)?;
let (parties, poly_commitments): (Vec<_>, Vec<_>) = parties
.into_iter()
.map(|p| p.apply_challenge_with_rng(&bit_challenge, rng))
.unzip();
let (dealer, poly_challenge) = dealer.receive_poly_commitments(poly_commitments)?;
let proof_shares: Vec<_> = parties
.into_iter()
.map(|p| p.apply_challenge(&poly_challenge))
// Collect the iterator of Results into a Result<Vec>, then unwrap it
.collect::<Result<Vec<_>, _>>()?;
let proof = dealer.receive_trusted_shares(&proof_shares)?;
Ok((proof, value_commitments))
}
/// Create a rangeproof for a set of values.
/// This is a convenience wrapper around [`RangeProof::prove_multiple_with_rng`],
/// passing in a threadsafe RNG.
#[cfg(feature = "std")]
pub fn prove_multiple(
bp_gens: &BulletproofGens,
pc_gens: &PedersenGens,
transcript: &mut Transcript,
values: &[u64],
blindings: &[Scalar],
n: usize,
) -> Result<(RangeProof, Vec<CompressedRistretto>), ProofError> {
RangeProof::prove_multiple_with_rng(
bp_gens,
pc_gens,
transcript,
values,
blindings,
n,
&mut thread_rng(),
)
}
/// Verifies a rangeproof for a given value commitment \\(V\\).
///
/// This is a convenience wrapper around `verify_multiple` for the `m=1` case.
pub fn verify_single_with_rng<T: RngCore + CryptoRng>(
&self,
bp_gens: &BulletproofGens,
pc_gens: &PedersenGens,
transcript: &mut Transcript,
V: &CompressedRistretto,
n: usize,
rng: &mut T,
) -> Result<(), ProofError> {
self.verify_multiple_with_rng(bp_gens, pc_gens, transcript, &[*V], n, rng)
}
/// Verifies a rangeproof for a given value commitment \\(V\\).
///
/// This is a convenience wrapper around [`RangeProof::verify_single_with_rng`],
/// passing in a threadsafe RNG.
#[cfg(feature = "std")]
pub fn verify_single(
&self,
bp_gens: &BulletproofGens,
pc_gens: &PedersenGens,
transcript: &mut Transcript,
V: &CompressedRistretto,
n: usize,
) -> Result<(), ProofError> {
self.verify_single_with_rng(bp_gens, pc_gens, transcript, V, n, &mut thread_rng())
}
/// Verifies an aggregated rangeproof for the given value commitments.
pub fn verify_multiple_with_rng<T: RngCore + CryptoRng>(
&self,
bp_gens: &BulletproofGens,
pc_gens: &PedersenGens,
transcript: &mut Transcript,
value_commitments: &[CompressedRistretto],
n: usize,
rng: &mut T,
) -> Result<(), ProofError> {
let m = value_commitments.len();
// First, replay the "interactive" protocol using the proof
// data to recompute all challenges.
if !(n == 8 || n == 16 || n == 32 || n == 64) {
return Err(ProofError::InvalidBitsize);
}
if bp_gens.gens_capacity < n {
return Err(ProofError::InvalidGeneratorsLength);
}
if bp_gens.party_capacity < m {
return Err(ProofError::InvalidGeneratorsLength);
}
transcript.rangeproof_domain_sep(n as u64, m as u64);
for V in value_commitments.iter() {
// Allow the commitments to be zero (0 value, 0 blinding)
// See https://github.com/dalek-cryptography/bulletproofs/pull/248#discussion_r255167177
transcript.append_point(b"V", V);
}
transcript.validate_and_append_point(b"A", &self.A)?;
transcript.validate_and_append_point(b"S", &self.S)?;
let y = transcript.challenge_scalar(b"y");
let z = transcript.challenge_scalar(b"z");
let zz = z * z;
let minus_z = -z;
transcript.validate_and_append_point(b"T_1", &self.T_1)?;
transcript.validate_and_append_point(b"T_2", &self.T_2)?;
let x = transcript.challenge_scalar(b"x");
transcript.append_scalar(b"t_x", &self.t_x);
transcript.append_scalar(b"t_x_blinding", &self.t_x_blinding);
transcript.append_scalar(b"e_blinding", &self.e_blinding);
let w = transcript.challenge_scalar(b"w");
// Challenge value for batching statements to be verified
let c = Scalar::random(rng);
let (x_sq, x_inv_sq, s) = self.ipp_proof.verification_scalars(n * m, transcript)?;
let s_inv = s.iter().rev();
let a = self.ipp_proof.a;
let b = self.ipp_proof.b;
// Construct concat_z_and_2, an iterator of the values of
// z^0 * \vec(2)^n || z^1 * \vec(2)^n || ... || z^(m-1) * \vec(2)^n
let powers_of_2: Vec<Scalar> = util::exp_iter(Scalar::from(2u64)).take(n).collect();
let concat_z_and_2: Vec<Scalar> = util::exp_iter(z)
.take(m)
.flat_map(|exp_z| powers_of_2.iter().map(move |exp_2| exp_2 * exp_z))
.collect();
let g = s.iter().map(|s_i| minus_z - a * s_i);
let h = s_inv
.zip(util::exp_iter(y.invert()))
.zip(concat_z_and_2.iter())
.map(|((s_i_inv, exp_y_inv), z_and_2)| z + exp_y_inv * (zz * z_and_2 - b * s_i_inv));
let value_commitment_scalars = util::exp_iter(z).take(m).map(|z_exp| c * zz * z_exp);
let basepoint_scalar = w * (self.t_x - a * b) + c * (delta(n, m, &y, &z) - self.t_x);
use curve25519_dalek::traits::VartimeMultiscalarMul;
let mega_check = RistrettoPoint::optional_multiscalar_mul(
iter::once(Scalar::ONE)
.chain(iter::once(x))
.chain(iter::once(c * x))
.chain(iter::once(c * x * x))
.chain(x_sq.iter().cloned())
.chain(x_inv_sq.iter().cloned())
.chain(iter::once(-self.e_blinding - c * self.t_x_blinding))
.chain(iter::once(basepoint_scalar))
.chain(g)
.chain(h)
.chain(value_commitment_scalars),
iter::once(self.A.decompress())
.chain(iter::once(self.S.decompress()))
.chain(iter::once(self.T_1.decompress()))
.chain(iter::once(self.T_2.decompress()))
.chain(self.ipp_proof.L_vec.iter().map(|L| L.decompress()))
.chain(self.ipp_proof.R_vec.iter().map(|R| R.decompress()))
.chain(iter::once(Some(pc_gens.B_blinding)))
.chain(iter::once(Some(pc_gens.B)))
.chain(bp_gens.G(n, m).map(|&x| Some(x)))
.chain(bp_gens.H(n, m).map(|&x| Some(x)))
.chain(value_commitments.iter().map(|V| V.decompress())),
)
.ok_or_else(|| ProofError::VerificationError)?;
use group::Group;
if mega_check.is_identity().into() {
Ok(())
} else {
Err(ProofError::VerificationError)
}
}
/// Verifies an aggregated rangeproof for the given value commitments.
/// This is a convenience wrapper around [`RangeProof::verify_multiple_with_rng`],
/// passing in a threadsafe RNG.
#[cfg(feature = "std")]
pub fn verify_multiple(
&self,
bp_gens: &BulletproofGens,
pc_gens: &PedersenGens,
transcript: &mut Transcript,
value_commitments: &[CompressedRistretto],
n: usize,
) -> Result<(), ProofError> {
self.verify_multiple_with_rng(
bp_gens,
pc_gens,
transcript,
value_commitments,
n,
&mut thread_rng(),
)
}
/// Serializes the proof into a byte array of \\(2 \lg n + 9\\)
/// 32-byte elements, where \\(n\\) is the number of secret bits.
///
/// # Layout
///
/// The layout of the range proof encoding is:
///
/// * four compressed Ristretto points \\(A,S,T_1,T_2\\),
/// * three scalars \\(t_x, \tilde{t}_x, \tilde{e}\\),
/// * \\(n\\) pairs of compressed Ristretto points \\(L_0,R_0\dots,L_{n-1},R_{n-1}\\),
/// * two scalars \\(a, b\\).
pub fn to_bytes(&self) -> Vec<u8> {
// 7 elements: points A, S, T1, T2, scalars tx, tx_bl, e_bl.
let mut buf = Vec::with_capacity(7 * 32 + self.ipp_proof.serialized_size());
buf.extend_from_slice(self.A.as_bytes());
buf.extend_from_slice(self.S.as_bytes());
buf.extend_from_slice(self.T_1.as_bytes());
buf.extend_from_slice(self.T_2.as_bytes());
buf.extend_from_slice(self.t_x.as_bytes());
buf.extend_from_slice(self.t_x_blinding.as_bytes());
buf.extend_from_slice(self.e_blinding.as_bytes());
buf.extend(self.ipp_proof.to_bytes_iter());
buf
}
/// Deserializes the proof from a byte slice.
///
/// Returns an error if the byte slice cannot be parsed into a `RangeProof`.
pub fn from_bytes(slice: &[u8]) -> Result<RangeProof, ProofError> {
if slice.len() % 32 != 0 {
return Err(ProofError::FormatError);
}
if slice.len() < 7 * 32 {
return Err(ProofError::FormatError);
}
use crate::util::read32;
let A = CompressedRistretto(read32(&slice[0 * 32..]));
let S = CompressedRistretto(read32(&slice[1 * 32..]));
let T_1 = CompressedRistretto(read32(&slice[2 * 32..]));
let T_2 = CompressedRistretto(read32(&slice[3 * 32..]));
let t_x = Option::from(Scalar::from_canonical_bytes(read32(&slice[4 * 32..])))
.ok_or(ProofError::FormatError)?;
let t_x_blinding = Option::from(Scalar::from_canonical_bytes(read32(&slice[5 * 32..])))
.ok_or(ProofError::FormatError)?;
let e_blinding = Option::from(Scalar::from_canonical_bytes(read32(&slice[6 * 32..])))
.ok_or(ProofError::FormatError)?;
let ipp_proof = InnerProductProof::from_bytes(&slice[7 * 32..])?;
Ok(RangeProof {
A,
S,
T_1,
T_2,
t_x,
t_x_blinding,
e_blinding,
ipp_proof,
})
}
}
impl Serialize for RangeProof {
fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
where
S: Serializer,
{
serializer.serialize_bytes(&self.to_bytes()[..])
}
}
impl<'de> Deserialize<'de> for RangeProof {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: Deserializer<'de>,
{
struct RangeProofVisitor;
impl<'de> Visitor<'de> for RangeProofVisitor {
type Value = RangeProof;
fn expecting(&self, formatter: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
formatter.write_str("a valid RangeProof")
}
fn visit_bytes<E>(self, v: &[u8]) -> Result<RangeProof, E>
where
E: serde::de::Error,
{
// Using Error::custom requires T: Display, which our error
// type only implements when it implements std::error::Error.
#[cfg(feature = "std")]
return RangeProof::from_bytes(v).map_err(serde::de::Error::custom);
// In no-std contexts, drop the error message.
#[cfg(not(feature = "std"))]
return RangeProof::from_bytes(v)
.map_err(|_| serde::de::Error::custom("deserialization error"));
}
}
deserializer.deserialize_bytes(RangeProofVisitor)
}
}
/// Compute
/// \\[
/// \delta(y,z) = (z - z^{2}) \langle \mathbf{1}, {\mathbf{y}}^{n \cdot m} \rangle - \sum_{j=0}^{m-1} z^{j+3} \cdot \langle \mathbf{1}, {\mathbf{2}}^{n \cdot m} \rangle
/// \\]
fn delta(n: usize, m: usize, y: &Scalar, z: &Scalar) -> Scalar {
let sum_y = util::sum_of_powers(y, n * m);
let sum_2 = util::sum_of_powers(&Scalar::from(2u64), n);
let sum_z = util::sum_of_powers(z, m);
(z - z * z) * sum_y - z * z * z * sum_2 * sum_z
}
#[cfg(test)]
mod tests {
use super::*;
use crate::generators::PedersenGens;
#[test]
fn test_delta() {
let mut rng = rand::thread_rng();
let y = Scalar::random(&mut rng);
let z = Scalar::random(&mut rng);
// Choose n = 256 to ensure we overflow the group order during
// the computation, to check that that's done correctly
let n = 256;
// code copied from previous implementation
let z2 = z * z;
let z3 = z2 * z;
let mut power_g = Scalar::ZERO;
let mut exp_y = Scalar::ONE; // start at y^0 = 1
let mut exp_2 = Scalar::ONE; // start at 2^0 = 1
for _ in 0..n {
power_g += (z - z2) * exp_y - z3 * exp_2;
exp_y = exp_y * y; // y^i -> y^(i+1)
exp_2 = exp_2 + exp_2; // 2^i -> 2^(i+1)
}
assert_eq!(power_g, delta(n, 1, &y, &z),);
}
/// Given a bitsize `n`, test the following:
///
/// 1. Generate `m` random values and create a proof they are all in range;
/// 2. Serialize to wire format;
/// 3. Deserialize from wire format;
/// 4. Verify the proof.
fn singleparty_create_and_verify_helper(n: usize, m: usize) {
// Split the test into two scopes, so that it's explicit what
// data is shared between the prover and the verifier.
// Use bincode for serialization
//use bincode; // already present in lib.rs
// Both prover and verifier have access to the generators and the proof
let max_bitsize = 64;
let max_parties = 8;
let pc_gens = PedersenGens::default();
let bp_gens = BulletproofGens::new(max_bitsize, max_parties);
// Prover's scope
let (proof_bytes, value_commitments) = {
use self::rand::Rng;
let mut rng = rand::thread_rng();
// 0. Create witness data
let (min, max) = (0u64, ((1u128 << n) - 1) as u64);
let values: Vec<u64> = (0..m).map(|_| rng.gen_range(min..max)).collect();
let blindings: Vec<Scalar> = (0..m).map(|_| Scalar::random(&mut rng)).collect();
// 1. Create the proof
let mut transcript = Transcript::new(b"AggregatedRangeProofTest");
let (proof, value_commitments) = RangeProof::prove_multiple(
&bp_gens,
&pc_gens,
&mut transcript,
&values,
&blindings,
n,
)
.unwrap();
// 2. Return serialized proof and value commitments
(bincode::serialize(&proof).unwrap(), value_commitments)
};
// Verifier's scope
{
// 3. Deserialize
let proof: RangeProof = bincode::deserialize(&proof_bytes).unwrap();
// 4. Verify with the same customization label as above
let mut transcript = Transcript::new(b"AggregatedRangeProofTest");
assert!(proof
.verify_multiple(&bp_gens, &pc_gens, &mut transcript, &value_commitments, n)
.is_ok());
}
}
#[test]
fn create_and_verify_n_32_m_1() {
singleparty_create_and_verify_helper(32, 1);
}
#[test]
fn create_and_verify_n_32_m_2() {
singleparty_create_and_verify_helper(32, 2);
}
#[test]
fn create_and_verify_n_32_m_4() {
singleparty_create_and_verify_helper(32, 4);
}
#[test]
fn create_and_verify_n_32_m_8() {
singleparty_create_and_verify_helper(32, 8);
}
#[test]
fn create_and_verify_n_64_m_1() {
singleparty_create_and_verify_helper(64, 1);
}
#[test]
fn create_and_verify_n_64_m_2() {
singleparty_create_and_verify_helper(64, 2);
}
#[test]
fn create_and_verify_n_64_m_4() {
singleparty_create_and_verify_helper(64, 4);
}
#[test]
fn create_and_verify_n_64_m_8() {
singleparty_create_and_verify_helper(64, 8);
}
#[test]
fn detect_dishonest_party_during_aggregation() {
use self::dealer::*;
use self::party::*;
use crate::errors::MPCError;
// Simulate four parties, two of which will be dishonest and use a 64-bit value.
let m = 4;
let n = 32;
let pc_gens = PedersenGens::default();
let bp_gens = BulletproofGens::new(n, m);
use self::rand::Rng;
let mut rng = rand::thread_rng();
let mut transcript = Transcript::new(b"AggregatedRangeProofTest");
// Parties 0, 2 are honest and use a 32-bit value
let v0 = rng.gen::<u32>() as u64;
let v0_blinding = Scalar::random(&mut rng);
let party0 = Party::new(&bp_gens, &pc_gens, v0, v0_blinding, n).unwrap();
let v2 = rng.gen::<u32>() as u64;
let v2_blinding = Scalar::random(&mut rng);
let party2 = Party::new(&bp_gens, &pc_gens, v2, v2_blinding, n).unwrap();
// Parties 1, 3 are dishonest and use a 64-bit value
let v1 = rng.gen::<u64>();
let v1_blinding = Scalar::random(&mut rng);
let party1 = Party::new(&bp_gens, &pc_gens, v1, v1_blinding, n).unwrap();
let v3 = rng.gen::<u64>();
let v3_blinding = Scalar::random(&mut rng);
let party3 = Party::new(&bp_gens, &pc_gens, v3, v3_blinding, n).unwrap();
let dealer = Dealer::new(&bp_gens, &pc_gens, &mut transcript, n, m).unwrap();
let (party0, bit_com0) = party0.assign_position(0).unwrap();
let (party1, bit_com1) = party1.assign_position(1).unwrap();
let (party2, bit_com2) = party2.assign_position(2).unwrap();
let (party3, bit_com3) = party3.assign_position(3).unwrap();
let (dealer, bit_challenge) = dealer
.receive_bit_commitments(vec![bit_com0, bit_com1, bit_com2, bit_com3])
.unwrap();
let (party0, poly_com0) = party0.apply_challenge(&bit_challenge);
let (party1, poly_com1) = party1.apply_challenge(&bit_challenge);
let (party2, poly_com2) = party2.apply_challenge(&bit_challenge);
let (party3, poly_com3) = party3.apply_challenge(&bit_challenge);
let (dealer, poly_challenge) = dealer
.receive_poly_commitments(vec![poly_com0, poly_com1, poly_com2, poly_com3])
.unwrap();
let share0 = party0.apply_challenge(&poly_challenge).unwrap();
let share1 = party1.apply_challenge(&poly_challenge).unwrap();
let share2 = party2.apply_challenge(&poly_challenge).unwrap();
let share3 = party3.apply_challenge(&poly_challenge).unwrap();
match dealer.receive_shares(&[share0, share1, share2, share3]) {
Err(MPCError::MalformedProofShares { bad_shares }) => {
assert_eq!(bad_shares, vec![1, 3]);
}
Err(_) => {
panic!("Got wrong error type from malformed shares");
}
Ok(_) => {
panic!("The proof was malformed, but it was not detected");
}
}
}
#[test]
fn detect_dishonest_dealer_during_aggregation() {
use self::dealer::*;
use self::party::*;
use crate::errors::MPCError;
// Simulate one party
let m = 1;
let n = 32;
let pc_gens = PedersenGens::default();
let bp_gens = BulletproofGens::new(n, m);
use self::rand::Rng;
let mut rng = rand::thread_rng();
let mut transcript = Transcript::new(b"AggregatedRangeProofTest");
let v0 = rng.gen::<u32>() as u64;
let v0_blinding = Scalar::random(&mut rng);
let party0 = Party::new(&bp_gens, &pc_gens, v0, v0_blinding, n).unwrap();
let dealer = Dealer::new(&bp_gens, &pc_gens, &mut transcript, n, m).unwrap();
// Now do the protocol flow as normal....
let (party0, bit_com0) = party0.assign_position(0).unwrap();
let (dealer, bit_challenge) = dealer.receive_bit_commitments(vec![bit_com0]).unwrap();
let (party0, poly_com0) = party0.apply_challenge(&bit_challenge);
let (_dealer, mut poly_challenge) =
dealer.receive_poly_commitments(vec![poly_com0]).unwrap();
// But now simulate a malicious dealer choosing x = 0
poly_challenge.x = Scalar::ZERO;
let maybe_share0 = party0.apply_challenge(&poly_challenge);
assert!(maybe_share0.unwrap_err() == MPCError::MaliciousDealer);
}
}