fix(mmcs): fix bugs

src/mmcs.py

@@ -36,9 +36,10 @@ def commit(cls, vecs, debug=False):
             layers.append([cls.compress((layers[i-1][j], layers[i-1][j+1]), debug) for j in range(0, len(layers[i-1]), 2)])
             layers[-1] = [cls.compress((layers[-1][j], cls.hash(vecs[i][j])), debug) for j in range(len(layers[-1]))]
 
-        for i in range(log_2(min_height)):
+        for i in range(len(vecs), len(vecs) + log_2(min_height)):
             layers.append([cls.compress((layers[i-1][j], layers[i-1][j+1]), debug) for j in range(0, len(layers[i-1]), 2)])
             layers[-1] = [cls.compress((layers[-1][j], cls.default_digest), debug) for j in range(len(layers[-1]))]
+            print("layers[-1]:", layers[-1])
 
         return {
             'layers': layers,
@@ -48,28 +49,43 @@ def commit(cls, vecs, debug=False):
     @classmethod
     def open(cls, index, prover_data, debug=False):
         assert cls.configured, "MMCS is not configured"
+
         layers = prover_data['layers']
-        if debug: print(layers)
+        if debug:
+            print("layers:")
+            for layer in layers:
+                print(layer)
         vecs = prover_data['vecs']
-        if debug: print(vecs)
+        if debug:
+            print("vecs:")
+            for vec in vecs:
+                print(vec)
 
-        height = len(layers)
-        openings = [vecs[i][index >> (32 - len(vecs[i]))] for i in range(height)]
-        proof = [layers[i][(index >> (32 - len(layers[i]))) ^ 1] for i in range(height - 1)]
+        openings = [vecs[i][index >> (32 - log_2(len(vecs[i])))] for i in range(len(vecs))]
+        proof = [layers[i][(index >> (32 - log_2(len(layers[i])))) ^ 1] for i in range(len(layers) - 1)]
         root = layers[-1][0]
-        if debug: print(openings, proof, root)
+        if debug: print("openings:", openings)
+        if debug: print("proof:", proof)
+        if debug: print("root:", root)
         return openings, proof, root
 
     @classmethod
     def verify(cls, index, openings, proof, root, debug=False):
-        index >>= (32 - (1 << (len(openings) - 1)))
+        index >>= (32 - len(proof))
+        assert index < 1 << len(proof), f"index {index} is out of bounds"
+        if debug: print("index:", index)
         expected = cls.hash(openings[0])
-        index >>= 1
-        for i in range(1, len(openings)):
+        if debug: print("expected:", expected)
+        for i in range(1, 1 + len(proof)):
+            if debug: print("index:", index)
             if index & 1:
                 expected = cls.compress((proof[i-1], expected), debug)
             else:
                 expected = cls.compress((expected, proof[i-1]), debug)
-            expected = cls.compress((expected, cls.hash(openings[i])), debug)
+            if i > len(openings) - 1:
+                expected = cls.compress((expected, cls.default_digest), debug)
+            else:
+                expected = cls.compress((expected, cls.hash(openings[i])), debug)
             index >>= 1
+            if debug: print("expected:", expected)
         assert expected == root, f"expected {expected}, root {root}"

tests/test_mmcs.py

@@ -10,15 +10,16 @@
 class TestMMCS(TestCase):
     def setUp(self):
         def hash(x): return x
-        def compress(x): return x[0] + x[1]
+        def compress(x): return x[0] - x[1]
         MMCS.configure(hash, compress)
 
     def test_mmcs(self):
-        evals = [[randint(0, 2**32-1) for _ in range(1 << i)] for i in range(4)]
+        evals = [[randint(0, 2**32-1) for _ in range(4 * (1 << i))] for i in range(4)]
         evals = list(reversed(evals))
         prover_data = MMCS.commit(evals, debug=False)
-        openings, proof, root = MMCS.open(0, prover_data, debug=False)
-        MMCS.verify(0, openings, proof, root, debug=False)
+        idx = randint(0, 2 ** 32 - 1)
+        openings, proof, root = MMCS.open(idx, prover_data, debug=True)
+        MMCS.verify(idx, openings, proof, root, debug=True)
 
 if __name__ == "__main__":
     main()