calculate kzg challenge instead of accepting it as parameter

worldcoin · Sep 6, 2024 · f8bb6d0 · f8bb6d0
1 parent 985b052
commit f8bb6d0
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Showing 3 changed files with 15 additions and 19 deletions.
diff --git a/src/WorldIDIdentityManagerImplV3.sol b/src/WorldIDIdentityManagerImplV3.sol
@@ -102,7 +102,7 @@ contract WorldIDIdentityManagerImplV3 is WorldIDIdentityManagerImplV2 {
         /// @notice KZG proof associated with the commitment.
         uint128[3] kzgProof;
 
-        /// @notice Expected evaluation of the polynomial at a certain point equal to kzgChallenge.
+        /// @notice Expected evaluation of the polynomial at a certain point equal to KZG challenge.
         uint256 expectedEvaluation;
 
         /// @notice The value for the root of the tree before the `identityCommitments` have been inserted.
@@ -113,9 +113,6 @@ contract WorldIDIdentityManagerImplV3 is WorldIDIdentityManagerImplV2 {
         ///         by `preRoot`. Must be an element of the field `Kr`. (already in reduced form)
         uint256 postRoot;
 
-        /// @notice Challenge value used in the KZG proof to evaluate the polynomial.
-        uint256 kzgChallenge;
-
         /// @notice Hash of the input data calculated as described in the comment
         ///         to `calculateIdentityRegistrationInputHash()`.
         bytes32 inputHash;
@@ -174,9 +171,10 @@ contract WorldIDIdentityManagerImplV3 is WorldIDIdentityManagerImplV2 {
             // which it was expired.
             rootHistory[params.preRoot] = uint128(block.timestamp);
 
+            bytes32 kzgChallenge = computeKzgChallenge(params.inputHash, kzgCommitmentHash);
             bool success = evaluatePoint(
                 kzgCommitmentHash,
-                bytes32(params.kzgChallenge),
+                kzgChallenge,
                 bytes32(params.expectedEvaluation),
                 params.kzgCommitment,
                 params.kzgProof
@@ -225,4 +223,16 @@ contract WorldIDIdentityManagerImplV3 is WorldIDIdentityManagerImplV2 {
         (bool success, ) = PRECOMPILE_POINT_EVALUATION.staticcall(input);
         return success;
     }
+
+    /// @notice Converts input values to a KZG challenge.
+    /// @dev The challenge is defined as a bytes32 value of a keccak256 hash of the concatenated inputs reduced by BN254 modulus.
+    /// @param inputHash Hash of the input data calculated as described in the comment
+    ///        to `calculateIdentityRegistrationInputHash()`.
+    /// @param kzgCommitmentVersionedHash versioned hash of the KZG commitment.
+    /// @return challenge The reduced keccak256 hash.
+    function computeKzgChallenge(bytes32 inputHash, bytes32 kzgCommitmentVersionedHash) public pure returns (bytes32) {
+        bytes memory inputBytes = abi.encodePacked(inputHash, kzgCommitmentVersionedHash);
+        uint256 reducedHash = uint256(keccak256(inputBytes)) % SNARK_SCALAR_FIELD;
+        return bytes32(reducedHash);
+    }
 }
diff --git a/src/test/identity-manager/WorldIDIdentityManagerIdentityRegistration4844.t.sol b/src/test/identity-manager/WorldIDIdentityManagerIdentityRegistration4844.t.sol
@@ -60,7 +60,6 @@ contract WorldIDIdentityManagerIdentityRegistration4844 is WorldIDIdentityManage
             expectedEvaluation: insertionExpectedEvaluation,
             preRoot: insertionPreRoot,
             postRoot: insertionPostRoot4844,
-            kzgChallenge: kzgChallenge,
             inputHash: insertionInputHash4844,
             batchSize: uint32(identityCommitmentsSize),
             startIndex: startIndex
@@ -127,7 +126,6 @@ contract WorldIDIdentityManagerIdentityRegistration4844 is WorldIDIdentityManage
             expectedEvaluation: insertionExpectedEvaluation,
             preRoot: newPreRoot,
             postRoot: newPostRoot,
-            kzgChallenge: kzgChallenge,
             inputHash: insertionInputHash4844,
             batchSize: uint32(preparedIdents.length),
             startIndex: newStartIndex
@@ -193,7 +191,6 @@ contract WorldIDIdentityManagerIdentityRegistration4844 is WorldIDIdentityManage
             expectedEvaluation: insertionExpectedEvaluation,
             preRoot: newPreRoot,
             postRoot: newPostRoot,
-            kzgChallenge: kzgChallenge,
             inputHash: insertionInputHash4844,
             batchSize: uint32(preparedIdents.length),
             startIndex: newStartIndex
@@ -260,7 +257,6 @@ contract WorldIDIdentityManagerIdentityRegistration4844 is WorldIDIdentityManage
             expectedEvaluation: insertionExpectedEvaluation,
             preRoot: newPreRoot,
             postRoot: newPostRoot,
-            kzgChallenge: kzgChallenge,
             inputHash: insertionInputHash4844,
             batchSize: uint32(preparedIdents.length),
             startIndex: newStartIndex
@@ -310,7 +306,6 @@ contract WorldIDIdentityManagerIdentityRegistration4844 is WorldIDIdentityManage
             expectedEvaluation: insertionExpectedEvaluation,
             preRoot: newPreRoot,
             postRoot: newPostRoot,
-            kzgChallenge: kzgChallenge,
             inputHash: insertionInputHash4844,
             batchSize: uint32(identityCommitments.length),
             startIndex: newStartIndex
@@ -356,7 +351,6 @@ contract WorldIDIdentityManagerIdentityRegistration4844 is WorldIDIdentityManage
             expectedEvaluation: insertionExpectedEvaluation,
             preRoot: insertionPreRoot,
             postRoot: insertionPostRoot,
-            kzgChallenge: kzgChallenge,
             inputHash: insertionInputHash4844,
             batchSize: uint32(identityCommitments.length),
             startIndex: newStartIndex
@@ -408,7 +402,6 @@ contract WorldIDIdentityManagerIdentityRegistration4844 is WorldIDIdentityManage
             expectedEvaluation: insertionExpectedEvaluation,
             preRoot: insertionPreRoot,
             postRoot: insertionPostRoot,
-            kzgChallenge: kzgChallenge,
             inputHash: insertionInputHash4844,
             batchSize: uint32(identities.length),
             startIndex: startIndex
@@ -472,7 +465,6 @@ contract WorldIDIdentityManagerIdentityRegistration4844 is WorldIDIdentityManage
             expectedEvaluation: insertionExpectedEvaluation,
             preRoot: insertionPreRoot,
             postRoot: newPostRoot,
-            kzgChallenge: kzgChallenge,
             inputHash: insertionInputHash4844,
             batchSize: uint32(identityCommitments.length),
             startIndex: startIndex
@@ -504,7 +496,6 @@ contract WorldIDIdentityManagerIdentityRegistration4844 is WorldIDIdentityManage
             expectedEvaluation: insertionExpectedEvaluation,
             preRoot: insertionPreRoot,
             postRoot: insertionPostRoot,
-            kzgChallenge: kzgChallenge,
             inputHash: insertionInputHash4844,
             batchSize: uint32(identityCommitments.length),
             startIndex: startIndex
@@ -551,7 +542,6 @@ contract WorldIDIdentityManagerIdentityRegistration4844 is WorldIDIdentityManage
             expectedEvaluation: insertionExpectedEvaluation,
             preRoot: actualRoot,
             postRoot: insertionPostRoot,
-            kzgChallenge: kzgChallenge,
             inputHash: insertionInputHash4844,
             batchSize: uint32(identityCommitments.length),
             startIndex: startIndex
@@ -608,7 +598,6 @@ contract WorldIDIdentityManagerIdentityRegistration4844 is WorldIDIdentityManage
             expectedEvaluation: insertionExpectedEvaluation,
             preRoot: initialRoot,
             postRoot: insertionPostRoot,
-            kzgChallenge: kzgChallenge,
             inputHash: insertionInputHash4844,
             batchSize: uint32(identities.length),
             startIndex: startIndex
@@ -639,7 +628,6 @@ contract WorldIDIdentityManagerIdentityRegistration4844 is WorldIDIdentityManage
             expectedEvaluation: insertionExpectedEvaluation,
             preRoot: initialRoot,
             postRoot: insertionPostRoot,
-            kzgChallenge: kzgChallenge,
             inputHash: insertionInputHash4844,
             batchSize: uint32(identityCommitments.length),
             startIndex: startIndex

diff --git a/src/test/identity-manager/WorldIDIdentityManagerTest.sol b/src/test/identity-manager/WorldIDIdentityManagerTest.sol
@@ -80,8 +80,6 @@ contract WorldIDIdentityManagerTest is WorldIDTest {
         0x3d5d4a7d6098f2147ed77be69d93179e6179479b8771c2554e5404c06f836408;
     uint256 internal constant insertionPostRoot4844 =
         0x0c3f30b0604dae9a378e2bf62826bf5a772e9ad745df6f8c8256dff351fecee8;
-    uint256 internal constant kzgChallenge =
-        0x1b5f5a71803049342dbd89f27e11d537400e959eea99de6e29e262d22adc3468;
 
     uint256[8] insertionProof4844;
     uint256[2] commitments;