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Commit b82c844

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samkim-cryptosamkim-crypto
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add proof generation logic for confidential mint and burn
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‎token/confidential-transfer/proof-generation/src/burn.rs

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use {
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crate::{
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encryption::BurnAmountCiphertext, errors::TokenProofGenerationError,
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try_combine_lo_hi_ciphertexts, try_split_u64,
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},
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solana_zk_sdk::{
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encryption::{
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auth_encryption::{AeCiphertext, AeKey},
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elgamal::{ElGamalCiphertext, ElGamalKeypair, ElGamalPubkey},
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pedersen::Pedersen,
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},
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zk_elgamal_proof_program::proof_data::{
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BatchedGroupedCiphertext2HandlesValidityProofData, BatchedRangeProofU128Data,
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CiphertextCommitmentEqualityProofData,
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},
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},
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};
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const REMAINING_BALANCE_BIT_LENGTH: usize = 64;
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const BURN_AMOUNT_LO_BIT_LENGTH: usize = 16;
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const BURN_AMOUNT_HI_BIT_LENGTH: usize = 32;
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/// The padding bit length in range proofs to make the bit-length power-of-2
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const RANGE_PROOF_PADDING_BIT_LENGTH: usize = 16;
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/// The proof data required for a confidential burn instruction
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pub struct BurnProofData {
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pub equality_proof_data: CiphertextCommitmentEqualityProofData,
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pub ciphertext_validity_proof_data: BatchedGroupedCiphertext2HandlesValidityProofData,
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pub range_proof_data: BatchedRangeProofU128Data,
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}
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pub fn burn_split_proof_data(
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current_available_balance_ciphertext: &ElGamalCiphertext,
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current_decryptable_available_balance: &AeCiphertext,
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burn_amount: u64,
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source_elgamal_keypair: &ElGamalKeypair,
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aes_key: &AeKey,
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auditor_elgamal_pubkey: &ElGamalPubkey,
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) -> Result<BurnProofData, TokenProofGenerationError> {
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// split the burn amount into low and high bits
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let (burn_amount_lo, burn_amount_hi) = try_split_u64(burn_amount, BURN_AMOUNT_LO_BIT_LENGTH)
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.ok_or(TokenProofGenerationError::IllegalAmountBitLength)?;
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// encrypt the burn amount under the source and auditor's ElGamal public key
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let (burn_amount_ciphertext_lo, burn_amount_opening_lo) = BurnAmountCiphertext::new(
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burn_amount_lo,
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source_elgamal_keypair.pubkey(),
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auditor_elgamal_pubkey,
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);
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let (burn_amount_ciphertext_hi, burn_amount_opening_hi) = BurnAmountCiphertext::new(
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burn_amount_hi,
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source_elgamal_keypair.pubkey(),
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auditor_elgamal_pubkey,
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);
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// decrypt the current available balance at the source
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let current_decrypted_available_balance = current_decryptable_available_balance
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.decrypt(aes_key)
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.ok_or(TokenProofGenerationError::IllegalAmountBitLength)?;
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// copmute the remaining balance ciphertext
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let burn_amount_ciphertext_source_lo = burn_amount_ciphertext_lo
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.0
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.to_elgamal_ciphertext(0)
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.unwrap();
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let burn_amount_ciphertext_source_hi = burn_amount_ciphertext_hi
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.0
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.to_elgamal_ciphertext(0)
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.unwrap();
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#[allow(clippy::arithmetic_side_effects)]
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let new_available_balance_ciphertext = current_available_balance_ciphertext
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- try_combine_lo_hi_ciphertexts(
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&burn_amount_ciphertext_source_lo,
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&burn_amount_ciphertext_source_hi,
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BURN_AMOUNT_LO_BIT_LENGTH,
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)
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.ok_or(TokenProofGenerationError::IllegalAmountBitLength)?;
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// compute the remaining balance at the source
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let remaining_balance = current_decrypted_available_balance
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.checked_sub(burn_amount)
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.ok_or(TokenProofGenerationError::NotEnoughFunds)?;
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let (new_available_balance_commitment, new_available_balance_opening) =
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Pedersen::new(remaining_balance);
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// generate equality proof data
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let equality_proof_data = CiphertextCommitmentEqualityProofData::new(
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source_elgamal_keypair,
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&new_available_balance_ciphertext,
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&new_available_balance_commitment,
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&new_available_balance_opening,
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remaining_balance,
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)
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.map_err(TokenProofGenerationError::from)?;
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// generate ciphertext validity data
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let ciphertext_validity_proof_data = BatchedGroupedCiphertext2HandlesValidityProofData::new(
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source_elgamal_keypair.pubkey(),
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auditor_elgamal_pubkey,
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&burn_amount_ciphertext_lo.0,
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&burn_amount_ciphertext_hi.0,
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burn_amount_lo,
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burn_amount_hi,
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&burn_amount_opening_lo,
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&burn_amount_opening_hi,
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)
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.map_err(TokenProofGenerationError::from)?;
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// generate range proof data
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let (padding_commitment, padding_opening) = Pedersen::new(0_u64);
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let range_proof_data = BatchedRangeProofU128Data::new(
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vec![
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&new_available_balance_commitment,
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burn_amount_ciphertext_lo.get_commitment(),
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burn_amount_ciphertext_hi.get_commitment(),
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&padding_commitment,
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],
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vec![remaining_balance, burn_amount_lo, burn_amount_hi, 0],
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vec![
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REMAINING_BALANCE_BIT_LENGTH,
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BURN_AMOUNT_LO_BIT_LENGTH,
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BURN_AMOUNT_HI_BIT_LENGTH,
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RANGE_PROOF_PADDING_BIT_LENGTH,
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],
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vec![
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&new_available_balance_opening,
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&burn_amount_opening_lo,
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&burn_amount_opening_hi,
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&padding_opening,
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],
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)
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.map_err(TokenProofGenerationError::from)?;
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Ok(BurnProofData {
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equality_proof_data,
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ciphertext_validity_proof_data,
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range_proof_data,
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})
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}

‎token/confidential-transfer/proof-generation/src/encryption.rs

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Original file line numberDiff line numberDiff line change
@@ -86,3 +86,47 @@ impl FeeCiphertext {
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self.0.handles.get(1).unwrap()
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}
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}
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#[derive(Clone, Copy, Debug, Eq, PartialEq)]
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#[repr(C)]
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pub struct BurnAmountCiphertext(pub(crate) GroupedElGamalCiphertext<2>);
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impl BurnAmountCiphertext {
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pub fn new(
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amount: u64,
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source_pubkey: &ElGamalPubkey,
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auditor_pubkey: &ElGamalPubkey,
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) -> (Self, PedersenOpening) {
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let opening = PedersenOpening::new_rand();
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let grouped_ciphertext =
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GroupedElGamal::<2>::encrypt_with([source_pubkey, auditor_pubkey], amount, &opening);
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(Self(grouped_ciphertext), opening)
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}
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pub fn get_commitment(&self) -> &PedersenCommitment {
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&self.0.commitment
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}
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}
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#[derive(Clone, Copy, Debug, Eq, PartialEq)]
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#[repr(C)]
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pub struct MintAmountCiphertext(pub(crate) GroupedElGamalCiphertext<2>);
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impl MintAmountCiphertext {
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pub fn new(
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amount: u64,
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source_pubkey: &ElGamalPubkey,
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auditor_pubkey: &ElGamalPubkey,
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) -> (Self, PedersenOpening) {
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let opening = PedersenOpening::new_rand();
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let grouped_ciphertext =
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GroupedElGamal::<2>::encrypt_with([source_pubkey, auditor_pubkey], amount, &opening);
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(Self(grouped_ciphertext), opening)
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}
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pub fn get_commitment(&self) -> &PedersenCommitment {
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&self.0.commitment
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}
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}

‎token/confidential-transfer/proof-generation/src/lib.rs

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@@ -6,8 +6,10 @@ use {
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},
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};
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pub mod burn;
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pub mod encryption;
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pub mod errors;
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pub mod mint;
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pub mod transfer;
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pub mod transfer_with_fee;
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pub mod withdraw;

‎token/confidential-transfer/proof-generation/src/mint.rs

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use {
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crate::{encryption::MintAmountCiphertext, errors::TokenProofGenerationError, try_split_u64},
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solana_zk_sdk::{
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encryption::{elgamal::ElGamalPubkey, pedersen::Pedersen},
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zk_elgamal_proof_program::proof_data::{
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BatchedGroupedCiphertext2HandlesValidityProofData, BatchedRangeProofU64Data,
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},
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},
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};
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const MINT_AMOUNT_LO_BIT_LENGTH: usize = 16;
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const MINT_AMOUNT_HI_BIT_LENGTH: usize = 32;
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/// The padding bit length in range proofs to make the bit-length power-of-2
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const RANGE_PROOF_PADDING_BIT_LENGTH: usize = 16;
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/// The proof data required for a confidential mint instruction
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pub struct MintProofData {
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pub ciphertext_validity_proof_data: BatchedGroupedCiphertext2HandlesValidityProofData,
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pub range_proof_data: BatchedRangeProofU64Data,
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}
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pub fn mint_split_proof_data(
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mint_amount: u64,
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destination_elgamal_pubkey: &ElGamalPubkey,
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auditor_elgamal_pubkey: &ElGamalPubkey,
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) -> Result<MintProofData, TokenProofGenerationError> {
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// split the mint amount into low and high bits
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let (mint_amount_lo, mint_amount_hi) = try_split_u64(mint_amount, MINT_AMOUNT_LO_BIT_LENGTH)
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.ok_or(TokenProofGenerationError::IllegalAmountBitLength)?;
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// encrypt the mint amount under the destination and auditor's ElGamal public
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// keys
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let (mint_amount_grouped_ciphertext_lo, mint_amount_opening_lo) = MintAmountCiphertext::new(
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mint_amount_lo,
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destination_elgamal_pubkey,
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auditor_elgamal_pubkey,
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);
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let (mint_amount_grouped_ciphertext_hi, mint_amount_opening_hi) = MintAmountCiphertext::new(
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mint_amount_hi,
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destination_elgamal_pubkey,
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auditor_elgamal_pubkey,
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);
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// generate ciphertext validity proof data
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let ciphertext_validity_proof_data = BatchedGroupedCiphertext2HandlesValidityProofData::new(
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destination_elgamal_pubkey,
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auditor_elgamal_pubkey,
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&mint_amount_grouped_ciphertext_lo.0,
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&mint_amount_grouped_ciphertext_hi.0,
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mint_amount_lo,
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mint_amount_hi,
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&mint_amount_opening_lo,
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&mint_amount_opening_hi,
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)
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.map_err(TokenProofGenerationError::from)?;
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// generate range proof data
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let (padding_commitment, padding_opening) = Pedersen::new(0_u64);
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let range_proof_data = BatchedRangeProofU64Data::new(
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vec![
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mint_amount_grouped_ciphertext_lo.get_commitment(),
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mint_amount_grouped_ciphertext_hi.get_commitment(),
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&padding_commitment,
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],
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vec![mint_amount_lo, mint_amount_hi, 0],
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vec![
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MINT_AMOUNT_LO_BIT_LENGTH,
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MINT_AMOUNT_HI_BIT_LENGTH,
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RANGE_PROOF_PADDING_BIT_LENGTH,
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],
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vec![
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&mint_amount_opening_lo,
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&mint_amount_opening_hi,
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&padding_opening,
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],
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)
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.map_err(TokenProofGenerationError::from)?;
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Ok(MintProofData {
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ciphertext_validity_proof_data,
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range_proof_data,
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})
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}

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