add confidential burn proof extraction

Author: samkim-crypto

token/confidential-transfer/proof-extraction/src/burn.rs

@@ -0,0 +1,71 @@
+use {
+    crate::{encryption::PodBurnAmountCiphertext, errors::TokenProofExtractionError},
+    solana_zk_sdk::{
+        encryption::pod::elgamal::{PodElGamalCiphertext, PodElGamalPubkey},
+        zk_elgamal_proof_program::proof_data::{
+            BatchedRangeProofContext, CiphertextCommitmentEqualityProofContext,
+            GroupedCiphertext2HandlesValidityProofContext,
+        },
+    },
+};
+
+/// The public keys associated with a confidential burn
+pub struct BurnPubkeys {
+    pub source: PodElGamalPubkey,
+    pub auditor: PodElGamalPubkey,
+}
+
+/// The proof context information needed to process a confidential burn instruction
+pub struct BurnProofContext {
+    pub burn_amount_ciphertext: PodBurnAmountCiphertext,
+    pub burn_pubkeys: BurnPubkeys,
+    pub remaining_balance_ciphertext: PodElGamalCiphertext,
+}
+
+impl BurnProofContext {
+    pub fn verify_and_extract(
+        equality_proof_context: &CiphertextCommitmentEqualityProofContext,
+        ciphertext_validity_proof_context: &GroupedCiphertext2HandlesValidityProofContext,
+        range_proof_context: &BatchedRangeProofContext,
+    ) -> Result<Self, TokenProofExtractionError> {
+        let CiphertextCommitmentEqualityProofContext {
+            pubkey: source_elgamal_pubkey_from_equality_proof,
+            ciphertext: remaining_balance_ciphertext,
+            commitment: remaining_balance_commitment,
+        } = equality_proof_context;
+
+        let GroupedCiphertext2HandlesValidityProofContext {
+            first_pubkey: source_elgamal_pubkey_from_validity_proof,
+            second_pubkey: auditor_elgamal_pubkey,
+            grouped_ciphertext: burn_amount_ciphertext,
+        } = ciphertext_validity_proof_context;
+
+        let BatchedRangeProofContext {
+            commitments,
+            bit_lengths,
+        } = range_proof_context;
+
+        if source_elgamal_pubkey_from_equality_proof == source_elgamal_pubkey_from_validity_proof {
+            return Err(TokenProofExtractionError::ElGamalPubkeyMismatch);
+        }
+
+        if commitments.is_empty() || commitments[0] != *remaining_balance_commitment {
+            return Err(TokenProofExtractionError::PedersenCommitmentMismatch);
+        }
+
+        if bit_lengths.is_empty() || bit_lengths[0] != 64 {
+            return Err(TokenProofExtractionError::RangeProofLengthMismatch);
+        }
+
+        let burn_pubkeys = BurnPubkeys {
+            source: *source_elgamal_pubkey_from_equality_proof,
+            auditor: *auditor_elgamal_pubkey,
+        };
+
+        Ok(BurnProofContext {
+            burn_amount_ciphertext: PodBurnAmountCiphertext(*burn_amount_ciphertext),
+            burn_pubkeys,
+            remaining_balance_ciphertext: *remaining_balance_ciphertext,
+        })
+    }
+}

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

@@ -46,3 +46,7 @@ impl PodFeeCiphertext {
             .map_err(|_| TokenProofExtractionError::CiphertextExtraction)
     }
 }
+
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+#[repr(C)]
+pub struct PodBurnAmountCiphertext(pub(crate) PodGroupedElGamalCiphertext2Handles);

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

@@ -1,3 +1,4 @@
+pub mod burn;
 pub mod encryption;
 pub mod errors;
 pub mod transfer;