add withdraw proof extraction

Author: samkim-crypto

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

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

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

@@ -0,0 +1,53 @@
+use {
+    crate::errors::TokenProofExtractionError,
+    solana_zk_sdk::{
+        encryption::pod::elgamal::{PodElGamalCiphertext, PodElGamalPubkey},
+        zk_elgamal_proof_program::proof_data::{
+            BatchedRangeProofContext, CiphertextCommitmentEqualityProofContext,
+        },
+    },
+};
+
+const REMAINING_BALANCE_BIT_LENGTH: u8 = 64;
+
+pub struct WithdrawProofContext {
+    pub source_pubkey: PodElGamalPubkey,
+    pub remaining_balance_ciphertext: PodElGamalCiphertext,
+}
+
+impl WithdrawProofContext {
+    pub fn verify_and_extract(
+        equality_proof_context: &CiphertextCommitmentEqualityProofContext,
+        range_proof_context: &BatchedRangeProofContext,
+    ) -> Result<Self, TokenProofExtractionError> {
+        let CiphertextCommitmentEqualityProofContext {
+            pubkey: source_pubkey,
+            ciphertext: remaining_balance_ciphertext,
+            commitment: remaining_balance_commitment,
+        } = equality_proof_context;
+
+        let BatchedRangeProofContext {
+            commitments: range_proof_commitments,
+            bit_lengths: range_proof_bit_lengths,
+        } = range_proof_context;
+
+        if range_proof_commitments.is_empty()
+            || range_proof_commitments[0] != *remaining_balance_commitment
+        {
+            return Err(TokenProofExtractionError::PedersenCommitmentMismatch);
+        }
+
+        if range_proof_bit_lengths.is_empty()
+            || range_proof_bit_lengths[0] != REMAINING_BALANCE_BIT_LENGTH
+        {
+            return Err(TokenProofExtractionError::RangeProofLengthMismatch);
+        }
+
+        let context_info = WithdrawProofContext {
+            source_pubkey: *source_pubkey,
+            remaining_balance_ciphertext: *remaining_balance_ciphertext,
+        };
+
+        Ok(context_info)
+    }
+}