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v1.16: [zk-token-sdk] Refactor ciphertext validity sigma proof and re…
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zk-token-sdk/src/sigma_proofs/batched_grouped_ciphertext_validity_proof.rs
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| Original file line number | Diff line number | Diff line change |
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| //! The ciphertext validity sigma proof system. | ||
| //! | ||
| //! The ciphertext validity proof is defined with respect to a Pedersen commitment and two | ||
| //! decryption handles. The proof certifies that a given Pedersen commitment can be decrypted using | ||
| //! ElGamal private keys that are associated with each of the two decryption handles. To generate | ||
| //! the proof, a prover must provide the Pedersen opening associated with the commitment. | ||
| //! | ||
| //! The protocol guarantees computational soundness (by the hardness of discrete log) and perfect | ||
| //! zero-knowledge in the random oracle model. | ||
| #[cfg(not(target_os = "solana"))] | ||
| use crate::encryption::{ | ||
| elgamal::{DecryptHandle, ElGamalPubkey}, | ||
| pedersen::{PedersenCommitment, PedersenOpening}, | ||
| }; | ||
| use { | ||
| crate::{ | ||
| sigma_proofs::{ | ||
| errors::ValidityProofError, | ||
| grouped_ciphertext_validity_proof::GroupedCiphertext2HandlesValidityProof, | ||
| }, | ||
| transcript::TranscriptProtocol, | ||
| }, | ||
| curve25519_dalek::scalar::Scalar, | ||
| merlin::Transcript, | ||
| }; | ||
|
|
||
| /// Batched grouped ciphertext validity proof with two handles. | ||
| /// | ||
| /// A batched grouped ciphertext validity proof certifies the validity of two instances of a | ||
| /// standard ciphertext validity proof. An instance of a standard validity proof consists of one | ||
| /// ciphertext and two decryption handles: `(commitment, destination_handle, auditor_handle)`. An | ||
| /// instance of a batched ciphertext validity proof is a pair `(commitment_0, | ||
| /// destination_handle_0, auditor_handle_0)` and `(commitment_1, destination_handle_1, | ||
| /// auditor_handle_1)`. The proof certifies the analogous decryptable properties for each one of | ||
| /// these pairs of commitment and decryption handles. | ||
| #[allow(non_snake_case)] | ||
| #[derive(Clone)] | ||
| pub struct BatchedGroupedCiphertext2HandlesValidityProof(GroupedCiphertext2HandlesValidityProof); | ||
|
|
||
| #[allow(non_snake_case)] | ||
| #[cfg(not(target_os = "solana"))] | ||
| impl BatchedGroupedCiphertext2HandlesValidityProof { | ||
| /// Batched grouped ciphertext validity proof constructor. | ||
| /// | ||
| /// The function simply batches the input openings and invokes the standard grouped ciphertext | ||
| /// validity proof constructor. | ||
| pub fn new<T: Into<Scalar>>( | ||
| (destination_pubkey, auditor_pubkey): (&ElGamalPubkey, &ElGamalPubkey), | ||
| (amount_lo, amount_hi): (T, T), | ||
| (opening_lo, opening_hi): (&PedersenOpening, &PedersenOpening), | ||
| transcript: &mut Transcript, | ||
| ) -> Self { | ||
| transcript.batched_grouped_ciphertext_validity_proof_domain_sep(); | ||
|
|
||
| let t = transcript.challenge_scalar(b"t"); | ||
|
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| let batched_message = amount_lo.into() + amount_hi.into() * t; | ||
| let batched_opening = opening_lo + &(opening_hi * &t); | ||
|
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| BatchedGroupedCiphertext2HandlesValidityProof(GroupedCiphertext2HandlesValidityProof::new( | ||
| (destination_pubkey, auditor_pubkey), | ||
| batched_message, | ||
| &batched_opening, | ||
| transcript, | ||
| )) | ||
| } | ||
|
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||
| /// Batched grouped ciphertext validity proof verifier. | ||
| /// | ||
| /// The function does *not* hash the public keys, commitment, or decryption handles into the | ||
| /// transcript. For security, the caller (the main protocol) should hash these public | ||
| /// components prior to invoking this constructor. | ||
| /// | ||
| /// This function is randomized. It uses `OsRng` internally to generate random scalars. | ||
| pub fn verify( | ||
| self, | ||
| (destination_pubkey, auditor_pubkey): (&ElGamalPubkey, &ElGamalPubkey), | ||
| (commitment_lo, commitment_hi): (&PedersenCommitment, &PedersenCommitment), | ||
| (destination_handle_lo, destination_handle_hi): (&DecryptHandle, &DecryptHandle), | ||
| (auditor_handle_lo, auditor_handle_hi): (&DecryptHandle, &DecryptHandle), | ||
| transcript: &mut Transcript, | ||
| ) -> Result<(), ValidityProofError> { | ||
| transcript.batched_grouped_ciphertext_validity_proof_domain_sep(); | ||
|
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| let t = transcript.challenge_scalar(b"t"); | ||
|
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| let batched_commitment = commitment_lo + commitment_hi * t; | ||
| let destination_batched_handle = destination_handle_lo + destination_handle_hi * t; | ||
| let auditor_batched_handle = auditor_handle_lo + auditor_handle_hi * t; | ||
|
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| let BatchedGroupedCiphertext2HandlesValidityProof(validity_proof) = self; | ||
|
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| validity_proof.verify( | ||
| &batched_commitment, | ||
| (destination_pubkey, auditor_pubkey), | ||
| (&destination_batched_handle, &auditor_batched_handle), | ||
| transcript, | ||
| ) | ||
| } | ||
|
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||
| pub fn to_bytes(&self) -> [u8; 160] { | ||
| self.0.to_bytes() | ||
| } | ||
|
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| pub fn from_bytes(bytes: &[u8]) -> Result<Self, ValidityProofError> { | ||
| GroupedCiphertext2HandlesValidityProof::from_bytes(bytes).map(Self) | ||
| } | ||
| } | ||
|
|
||
| #[cfg(test)] | ||
| mod test { | ||
| use { | ||
| super::*, | ||
| crate::encryption::{elgamal::ElGamalKeypair, pedersen::Pedersen}, | ||
| }; | ||
|
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||
| #[test] | ||
| fn test_batched_grouped_ciphertext_validity_proof() { | ||
| let destination_pubkey = ElGamalKeypair::new_rand().public; | ||
| let auditor_pubkey = ElGamalKeypair::new_rand().public; | ||
|
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| let amount_lo: u64 = 55; | ||
| let amount_hi: u64 = 77; | ||
|
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| let (commitment_lo, open_lo) = Pedersen::new(amount_lo); | ||
| let (commitment_hi, open_hi) = Pedersen::new(amount_hi); | ||
|
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| let destination_handle_lo = destination_pubkey.decrypt_handle(&open_lo); | ||
| let destination_handle_hi = destination_pubkey.decrypt_handle(&open_hi); | ||
|
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| let auditor_handle_lo = auditor_pubkey.decrypt_handle(&open_lo); | ||
| let auditor_handle_hi = auditor_pubkey.decrypt_handle(&open_hi); | ||
|
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| let mut prover_transcript = Transcript::new(b"Test"); | ||
| let mut verifier_transcript = Transcript::new(b"Test"); | ||
|
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| let proof = BatchedGroupedCiphertext2HandlesValidityProof::new( | ||
| (&destination_pubkey, &auditor_pubkey), | ||
| (amount_lo, amount_hi), | ||
| (&open_lo, &open_hi), | ||
| &mut prover_transcript, | ||
| ); | ||
|
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||
| assert!(proof | ||
| .verify( | ||
| (&destination_pubkey, &auditor_pubkey), | ||
| (&commitment_lo, &commitment_hi), | ||
| (&destination_handle_lo, &destination_handle_hi), | ||
| (&auditor_handle_lo, &auditor_handle_hi), | ||
| &mut verifier_transcript, | ||
| ) | ||
| .is_ok()); | ||
| } | ||
| } |
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