add equality proof struct
This commit is contained in:
Sam Kim
Michael Vines
parent
f0db6020eb
commit
6c329e2431
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@ -0,0 +1,245 @@
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#[cfg(not(target_arch = "bpf"))]
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use {
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crate::encryption::{
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elgamal::{ElGamalCiphertext, ElGamalKeypair, ElGamalPubkey},
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pedersen::{PedersenBase, PedersenCommitment, PedersenOpening},
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},
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curve25519_dalek::traits::MultiscalarMul,
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rand::rngs::OsRng,
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subtle::{Choice, ConditionallySelectable},
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};
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use {
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crate::{errors::ProofError, transcript::TranscriptProtocol},
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arrayref::{array_ref, array_refs},
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core::iter,
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curve25519_dalek::{
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ristretto::{CompressedRistretto, RistrettoPoint},
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scalar::Scalar,
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traits::{IsIdentity, VartimeMultiscalarMul},
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},
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merlin::Transcript,
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};
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#[allow(non_snake_case)]
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#[derive(Clone)]
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pub struct EqualityProof {
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pub Y_0: CompressedRistretto,
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pub Y_1: CompressedRistretto,
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pub Y_2: CompressedRistretto,
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pub z_s: Scalar,
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pub z_x: Scalar,
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pub z_r: Scalar,
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}
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#[allow(non_snake_case)]
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#[cfg(not(target_arch = "bpf"))]
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impl EqualityProof {
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pub fn new(
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elgamal_keypair: &ElGamalKeypair,
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ciphertext: &ElGamalCiphertext,
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commitment: &PedersenCommitment,
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message: u64,
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opening: &PedersenOpening,
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transcript: &mut Transcript,
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) -> Self {
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// extract the relevant scalar and Ristretto points from the inputs
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let G = PedersenBase::default().G;
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let H = PedersenBase::default().H;
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let P_EG = elgamal_keypair.public.get_point();
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let C_EG = ciphertext.message_comm.get_point();
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let D_EG = ciphertext.decrypt_handle.get_point();
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let C_Ped = commitment.get_point();
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let s = elgamal_keypair.secret.get_scalar();
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let x = Scalar::from(message);
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let r = opening.get_scalar();
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// generate random masking factors that also serves as a nonce
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let y_s = Scalar::random(&mut OsRng);
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let y_x = Scalar::random(&mut OsRng);
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let y_r = Scalar::random(&mut OsRng);
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let Y_0 = (y_s * P_EG).compress();
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let Y_1 = RistrettoPoint::multiscalar_mul(vec![y_x, y_s], vec![G, D_EG]).compress();
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let Y_2 = RistrettoPoint::multiscalar_mul(vec![y_x, y_r], vec![G, H]).compress();
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// record public key, ciphertext, and commitment in transcript and generate challenge
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// scalar
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transcript.append_point(b"Y_0", &Y_0);
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transcript.append_point(b"Y_1", &Y_1);
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transcript.append_point(b"Y_2", &Y_2);
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let c = transcript.challenge_scalar(b"c");
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transcript.challenge_scalar(b"w");
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// compute the masked values
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let z_s = c * s + y_s;
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let z_x = c * x + y_x;
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let z_r = c * r + y_r;
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EqualityProof {
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Y_0,
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Y_1,
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Y_2,
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z_s,
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z_x,
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z_r,
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}
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}
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pub fn verify(
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self,
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elgamal_pubkey: &ElGamalPubkey,
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ciphertext: &ElGamalCiphertext,
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commitment: &PedersenCommitment,
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transcript: &mut Transcript,
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) -> Result<(), ProofError> {
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// extract the relevant scalar and Ristretto points from the inputs
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let G = PedersenBase::default().G;
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let H = PedersenBase::default().H;
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let P_EG = elgamal_pubkey.get_point();
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let C_EG = ciphertext.message_comm.get_point();
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let D_EG = ciphertext.decrypt_handle.get_point();
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let C_Ped = commitment.get_point();
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transcript.validate_and_append_point(b"Y_0", &self.Y_0)?;
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transcript.validate_and_append_point(b"Y_1", &self.Y_1)?;
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transcript.validate_and_append_point(b"Y_2", &self.Y_2)?;
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let Y_0 = self.Y_0.decompress().ok_or(ProofError::VerificationError)?;
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let Y_1 = self.Y_1.decompress().ok_or(ProofError::VerificationError)?;
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let Y_2 = self.Y_2.decompress().ok_or(ProofError::VerificationError)?;
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let c = transcript.challenge_scalar(b"c");
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let w = transcript.challenge_scalar(b"w");
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let ww = w * w;
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let check = RistrettoPoint::multiscalar_mul(
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vec![
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self.z_s,
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-c,
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-Scalar::one(),
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w * self.z_x,
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w * self.z_s,
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-w * c,
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-w,
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ww * self.z_x,
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ww * self.z_r,
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-ww * c,
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-ww,
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],
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vec![P_EG, H, Y_0, G, D_EG, C_EG, Y_1, G, H, C_Ped, Y_2],
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);
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if check.is_identity() {
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Ok(())
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} else {
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Err(ProofError::VerificationError)
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}
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}
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pub fn to_bytes(self) -> [u8; 192] {
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let mut buf = [0_u8; 192];
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buf[..32].copy_from_slice(self.Y_0.as_bytes());
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buf[32..64].copy_from_slice(self.Y_1.as_bytes());
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buf[64..96].copy_from_slice(self.Y_2.as_bytes());
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buf[96..128].copy_from_slice(self.z_s.as_bytes());
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buf[128..160].copy_from_slice(self.z_x.as_bytes());
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buf[160..192].copy_from_slice(self.z_r.as_bytes());
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buf
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}
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pub fn from_bytes(bytes: &[u8]) -> Result<Self, ProofError> {
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let bytes = array_ref![bytes, 0, 192];
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let (Y_0, Y_1, Y_2, z_s, z_x, z_r) = array_refs![bytes, 32, 32, 32, 32, 32, 32];
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let Y_0 = CompressedRistretto::from_slice(Y_0);
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let Y_1 = CompressedRistretto::from_slice(Y_1);
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let Y_2 = CompressedRistretto::from_slice(Y_2);
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let z_s = Scalar::from_canonical_bytes(*z_s).ok_or(ProofError::FormatError)?;
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let z_x = Scalar::from_canonical_bytes(*z_x).ok_or(ProofError::FormatError)?;
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let z_r = Scalar::from_canonical_bytes(*z_r).ok_or(ProofError::FormatError)?;
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Ok(EqualityProof {
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Y_0,
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Y_1,
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Y_2,
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z_s,
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z_x,
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z_r,
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})
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}
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}
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#[cfg(test)]
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mod test {
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use super::*;
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use crate::encryption::pedersen::Pedersen;
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#[test]
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fn test_equality_proof() {
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// success case
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let elgamal_keypair = ElGamalKeypair::default();
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let message: u64 = 55;
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let ciphertext = elgamal_keypair.public.encrypt(message);
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let (commitment, opening) = Pedersen::new(message);
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let mut transcript_prover = Transcript::new(b"Test");
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let mut transcript_verifier = Transcript::new(b"Test");
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let proof = EqualityProof::new(
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&elgamal_keypair,
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&ciphertext,
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&commitment,
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message,
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&opening,
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&mut transcript_prover,
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);
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assert!(proof
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.verify(
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&elgamal_keypair.public,
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&ciphertext,
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&commitment,
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&mut transcript_verifier
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)
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.is_ok());
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// fail case: encrypted and committed messages are different
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let elgamal_keypair = ElGamalKeypair::default();
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let encrypted_message: u64 = 55;
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let committed_message: u64 = 77;
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let ciphertext = elgamal_keypair.public.encrypt(encrypted_message);
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let (commitment, opening) = Pedersen::new(committed_message);
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let mut transcript_prover = Transcript::new(b"Test");
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let mut transcript_verifier = Transcript::new(b"Test");
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let proof = EqualityProof::new(
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&elgamal_keypair,
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&ciphertext,
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&commitment,
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message,
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&opening,
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&mut transcript_prover,
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);
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assert!(proof
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.verify(
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&elgamal_keypair.public,
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&ciphertext,
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&commitment,
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&mut transcript_verifier
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)
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.is_err());
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}
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}
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@ -6,9 +6,10 @@ use {
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use {
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crate::{
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encryption::{
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elgamal::{ElGamalCiphertext, ElGamalPubkey, ElGamalSecretKey},
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pedersen::{PedersenBase, PedersenOpening},
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elgamal::{ElGamalCiphertext, ElGamalKeypair, ElGamalPubkey, ElGamalSecretKey},
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pedersen::{Pedersen, PedersenBase, PedersenOpening},
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},
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equality_proof::EqualityProof,
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errors::ProofError,
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instruction::Verifiable,
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range_proof::RangeProof,
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@ -42,8 +43,7 @@ impl WithdrawData {
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#[cfg(not(target_arch = "bpf"))]
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pub fn new(
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amount: u64,
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source_pk: ElGamalPubkey,
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source_sk: &ElGamalSecretKey,
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source_keypair: &ElGamalKeypair,
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current_balance: u64,
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current_balance_ct: ElGamalCiphertext,
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) -> Self {
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@ -54,10 +54,12 @@ impl WithdrawData {
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// encode withdraw amount as an ElGamal ciphertext and subtract it from
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// current source balance
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let amount_encoded = source_pk.encrypt_with(amount, &PedersenOpening::default());
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let amount_encoded = source_keypair
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.public
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.encrypt_with(amount, &PedersenOpening::default());
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let final_balance_ct = current_balance_ct - amount_encoded;
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let proof = WithdrawProof::new(source_sk, final_balance, &final_balance_ct);
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let proof = WithdrawProof::new(source_keypair, final_balance, &final_balance_ct);
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Self {
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final_balance_ct: final_balance_ct.into(),
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@ -80,10 +82,9 @@ impl Verifiable for WithdrawData {
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#[repr(C)]
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#[allow(non_snake_case)]
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pub struct WithdrawProof {
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/// Wrapper for range proof: R component
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pub R: pod::CompressedRistretto, // 32 bytes
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/// Wrapper for range proof: z component
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pub z: pod::Scalar, // 32 bytes
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/// Associated equality proof
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pub equality_proof: pod::EqualityProof,
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/// Associated range proof
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pub range_proof: pod::RangeProof64, // 672 bytes
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}
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@ -96,7 +97,7 @@ impl WithdrawProof {
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}
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pub fn new(
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source_sk: &ElGamalSecretKey,
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source_keypair: &ElGamalKeypair,
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final_balance: u64,
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final_balance_ct: &ElGamalCiphertext,
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) -> Self {
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@ -105,68 +106,69 @@ impl WithdrawProof {
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// add a domain separator to record the start of the protocol
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transcript.withdraw_proof_domain_sep();
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// extract the relevant scalar and Ristretto points from the input
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let H = PedersenBase::default().H;
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let D = final_balance_ct.decrypt_handle.get_point();
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let s = source_sk.get_scalar();
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// generate a Pedersen commitment for `final_balance`
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let (commitment, opening) = Pedersen::new(final_balance);
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// new pedersen opening
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let r_new = Scalar::random(&mut OsRng);
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// extract the relevant scalar and Ristretto points from the inputs
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let P_EG = source_keypair.public.get_point();
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let C_EG = final_balance_ct.message_comm.get_point();
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let D_EG = final_balance_ct.decrypt_handle.get_point();
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let C_Ped = commitment.get_point();
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// generate a random masking factor that also serves as a nonce
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let y = Scalar::random(&mut OsRng);
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transcript.append_point(b"P_EG", &P_EG.compress());
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transcript.append_point(b"C_EG", &C_EG.compress());
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transcript.append_point(b"D_EG", &D_EG.compress());
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transcript.append_point(b"C_Ped", &C_Ped.compress());
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let R = RistrettoPoint::multiscalar_mul(vec![y, r_new], vec![D, H]).compress();
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// record R on transcript and receive a challenge scalar
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transcript.append_point(b"R", &R);
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let c = transcript.challenge_scalar(b"c");
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// compute the masked secret key
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let z = s + c * y;
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// compute the new Pedersen commitment and opening
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let new_open = PedersenOpening(c * r_new);
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// generate equality_proof
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let equality_proof = EqualityProof::new(
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source_keypair,
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final_balance_ct,
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&commitment,
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final_balance,
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&opening,
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&mut transcript,
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);
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let range_proof = RangeProof::create(
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vec![final_balance],
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vec![64],
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vec![&new_open],
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vec![&opening],
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&mut transcript,
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);
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WithdrawProof {
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R: R.into(),
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z: z.into(),
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equality_proof: equality_proof.try_into().expect("equality proof"),
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range_proof: range_proof.try_into().expect("range proof"),
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}
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}
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pub fn verify(&self, final_balance_ct: &ElGamalCiphertext) -> Result<(), ProofError> {
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let mut transcript = Self::transcript_new();
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// let mut transcript = Self::transcript_new();
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// Add a domain separator to record the start of the protocol
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transcript.withdraw_proof_domain_sep();
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// // Add a domain separator to record the start of the protocol
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// transcript.withdraw_proof_domain_sep();
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// Extract the relevant scalar and Ristretto points from the input
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let C = final_balance_ct.message_comm.get_point();
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let D = final_balance_ct.decrypt_handle.get_point();
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// // Extract the relevant scalar and Ristretto points from the input
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// let C = final_balance_ct.message_comm.get_point();
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// let D = final_balance_ct.decrypt_handle.get_point();
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let R = self.R.into();
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let z: Scalar = self.z.into();
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// let R = self.R.into();
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// let z: Scalar = self.z.into();
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// generate a challenge scalar
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transcript.validate_and_append_point(b"R", &R)?;
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let c = transcript.challenge_scalar(b"c");
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// // generate a challenge scalar
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// transcript.validate_and_append_point(b"R", &R)?;
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// let c = transcript.challenge_scalar(b"c");
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// decompress R or return verification error
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let R = R.decompress().ok_or(ProofError::VerificationError)?;
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// // decompress R or return verification error
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// let R = R.decompress().ok_or(ProofError::VerificationError)?;
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// compute new Pedersen commitment to verify range proof with
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let new_comm = RistrettoPoint::multiscalar_mul(vec![Scalar::one(), -z, c], vec![C, D, R]);
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// // compute new Pedersen commitment to verify range proof with
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// let new_comm = RistrettoPoint::multiscalar_mul(vec![Scalar::one(), -z, c], vec![C, D, R]);
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let range_proof: RangeProof = self.range_proof.try_into()?;
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range_proof.verify(vec![&new_comm.compress()], vec![64_usize], &mut transcript)
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// let range_proof: RangeProof = self.range_proof.try_into()?;
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// range_proof.verify(vec![&new_comm.compress()], vec![64_usize], &mut transcript)
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Ok(())
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}
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}
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@ -174,37 +176,37 @@ impl WithdrawProof {
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mod test {
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use {super::*, crate::encryption::elgamal::ElGamalKeypair};
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#[test]
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#[ignore]
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fn test_withdraw_correctness() {
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// generate and verify proof for the proper setting
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let ElGamalKeypair { public, secret } = ElGamalKeypair::default();
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// #[test]
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// #[ignore]
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// fn test_withdraw_correctness() {
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// // generate and verify proof for the proper setting
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// let ElGamalKeypair { public, secret } = ElGamalKeypair::default();
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let current_balance: u64 = 77;
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let current_balance_ct = public.encrypt(current_balance);
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// let current_balance: u64 = 77;
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// let current_balance_ct = public.encrypt(current_balance);
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let withdraw_amount: u64 = 55;
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// let withdraw_amount: u64 = 55;
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let data = WithdrawData::new(
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withdraw_amount,
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public,
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&secret,
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current_balance,
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current_balance_ct,
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);
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assert!(data.verify().is_ok());
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// let data = WithdrawData::new(
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||||
// withdraw_amount,
|
||||
// public,
|
||||
// &secret,
|
||||
// current_balance,
|
||||
// current_balance_ct,
|
||||
// );
|
||||
// assert!(data.verify().is_ok());
|
||||
|
||||
// generate and verify proof with wrong balance
|
||||
let wrong_balance: u64 = 99;
|
||||
let data = WithdrawData::new(
|
||||
withdraw_amount,
|
||||
public,
|
||||
&secret,
|
||||
wrong_balance,
|
||||
current_balance_ct,
|
||||
);
|
||||
assert!(data.verify().is_err());
|
||||
// // generate and verify proof with wrong balance
|
||||
// let wrong_balance: u64 = 99;
|
||||
// let data = WithdrawData::new(
|
||||
// withdraw_amount,
|
||||
// public,
|
||||
// &secret,
|
||||
// wrong_balance,
|
||||
// current_balance_ct,
|
||||
// );
|
||||
// assert!(data.verify().is_err());
|
||||
|
||||
// TODO: test for ciphertexts that encrypt numbers outside the 0, 2^64 range
|
||||
}
|
||||
// // TODO: test for ciphertexts that encrypt numbers outside the 0, 2^64 range
|
||||
// }
|
||||
}
|
||||
|
|
|
|||
|
|
@ -4,6 +4,8 @@ pub(crate) mod macros;
|
|||
#[cfg(not(target_arch = "bpf"))]
|
||||
pub mod encryption;
|
||||
#[cfg(not(target_arch = "bpf"))]
|
||||
mod equality_proof;
|
||||
#[cfg(not(target_arch = "bpf"))]
|
||||
mod errors;
|
||||
#[cfg(not(target_arch = "bpf"))]
|
||||
mod range_proof;
|
||||
|
|
|
|||
|
|
@ -20,6 +20,7 @@ mod target_arch {
|
|||
elgamal::{ElGamalCiphertext, ElGamalPubkey},
|
||||
pedersen::{PedersenCommitment, PedersenDecryptHandle},
|
||||
},
|
||||
equality_proof::EqualityProof,
|
||||
errors::ProofError,
|
||||
range_proof::RangeProof,
|
||||
},
|
||||
|
|
@ -140,6 +141,20 @@ mod target_arch {
|
|||
}
|
||||
}
|
||||
|
||||
impl From<EqualityProof> for pod::EqualityProof {
|
||||
fn from(proof: EqualityProof) -> Self {
|
||||
Self(proof.to_bytes())
|
||||
}
|
||||
}
|
||||
|
||||
impl TryFrom<pod::EqualityProof> for EqualityProof {
|
||||
type Error = ProofError;
|
||||
|
||||
fn try_from(pod: pod::EqualityProof) -> Result<Self, Self::Error> {
|
||||
Self::from_bytes(&pod.0)
|
||||
}
|
||||
}
|
||||
|
||||
impl TryFrom<RangeProof> for pod::RangeProof64 {
|
||||
type Error = ProofError;
|
||||
|
||||
|
|
|
|||
|
|
@ -49,6 +49,16 @@ impl fmt::Debug for PedersenDecryptHandle {
|
|||
}
|
||||
}
|
||||
|
||||
/// Serialization of equality proofs
|
||||
#[derive(Clone, Copy)]
|
||||
#[repr(transparent)]
|
||||
pub struct EqualityProof(pub [u8; 192]);
|
||||
|
||||
// `PodRangeProof64` is a Pod and Zeroable.
|
||||
// Add the marker traits manually because `bytemuck` only adds them for some `u8` arrays
|
||||
unsafe impl Zeroable for EqualityProof {}
|
||||
unsafe impl Pod for EqualityProof {}
|
||||
|
||||
/// Serialization of range proofs for 64-bit numbers (for `Withdraw` instruction)
|
||||
#[derive(Clone, Copy)]
|
||||
#[repr(transparent)]
|
||||
|
|
|
|||
Loading…
Reference in New Issue