Added static method for verifying multiproof as well (#16)

Co-authored-by: Francisco Giordano <[email protected]>

Author: slavik0329

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## 1.0.4
+
+- Added `StandardMerkleTree.verifyMultiProof` static method.
+
 ## 1.0.3
 
 - Added `StandardMerkleTree.verify` static method for verification of a proof for given root, leaf, and leaf encoding.

README.md

@@ -157,6 +157,14 @@ const verified = StandardMerkleTree.verify(root, ['address', 'uint'], [alice, '1
 
 Returns a boolean that is `true` when the proof verifies that the value is contained in the tree given only the proof, merkle root, and encoding.
 
+### `StandardMerkleTree.verifyMultiProof`
+
+```typescript
+const isValid = StandardMerkleTree.verifyMultiProof(root, leafEncoding, multiproof);
+```
+
+Returns a boolean that is `true` when the multiproof verifies that all the values are contained in the tree given only the multiproof, merkle root, and leaf encoding.
+
 ### `StandardMerkleTree.load`
 
 ```typescript

src/standard.test.ts

@@ -65,6 +65,37 @@ describe('standard merkle tree', () => {
     }
   });
 
+  it('generates valid multi-proofs for all leaves from root and encoding', () => {
+    const { t } = characters('abcdef');
+    const leaves = Array.from(t.entries()).map(([_, leaf]) => leaf);
+
+    const multiproof = t.getMultiProof(leaves);
+
+    assert(StandardMerkleTree.verifyMultiProof(t.root, ['string'], multiproof));
+  });
+
+  it('rejects invalid multi-proof using static verifyMultiProof method', () => {
+    const { t } = characters('abcdef');
+    const { t: fakeTree } = characters('xyz');
+
+    const fakeLeaves = Array.from(fakeTree.entries()).map(([_, leaf]) => leaf);
+    const fakeMultiProof = fakeTree.getMultiProof(fakeLeaves);
+
+    assert(!StandardMerkleTree.verifyMultiProof(t.root, ['string'], fakeMultiProof));
+  });
+
+  it('verifies partial multi-proof using static verifyMultiProof method', () => {
+    const { t } = characters('abcdef');
+
+    const leaves = Array.from(t.entries())
+      .filter(([index]) => index % 2 === 0)
+      .map(([_, leaf]) => leaf);
+
+    const multiproof = t.getMultiProof(leaves);
+
+    assert(StandardMerkleTree.verifyMultiProof(t.root, ['string'], multiproof));
+  });
+
   it('renders tree representation', () => {
     const { t } = characters('abc');
 

src/standard.ts

@@ -66,6 +66,19 @@ export class StandardMerkleTree<T extends any[]> {
     return equalsBytes(impliedRoot, hexToBytes(root));
   }
 
+  static verifyMultiProof<T extends any[]>(root: string, leafEncoding: string[], multiproof: MultiProof<string, T>): boolean {
+    const leafHashes = multiproof.leaves.map(leaf => standardLeafHash(leaf, leafEncoding));
+    const proofBytes = multiproof.proof.map(hexToBytes);
+
+    const impliedRoot = processMultiProof({
+      leaves: leafHashes,
+      proof: proofBytes,
+      proofFlags: multiproof.proofFlags,
+    });
+
+    return equalsBytes(impliedRoot, hexToBytes(root));
+  }
+
   dump(): StandardMerkleTreeData<T> {
     return {
       format:      'standard-v1',