temp fix: little endian pedersen_hash (#103)

Author: gballet

trie/utils/verkle.go

@@ -70,7 +70,17 @@ func GetTreeKey(address []byte, treeIndex *uint256.Int, subIndex byte) []byte {
 
 	cfg, _ := verkle.GetConfig()
 	ret := cfg.CommitToPoly(poly[:], 0)
-	retb := ret.Bytes()
+
+	// The output of Byte() is big engian for banderwagon. This
+	// introduces an inbalance in the tree, because hashes are
+	// elements of a 253-bit field. This means more than half the
+	// tree would be empty. To avoid this problem, use a little
+	// endian commitment and chop the MSB.
+	var retb [32]byte
+	retb = ret.Bytes()
+	for i := 0; i < 16; i++ {
+		retb[31-i], retb[i] = retb[i], retb[31-i]
+	}
 	retb[31] = subIndex
 	return retb[:]
 

trie/verkle_test.go

@@ -386,7 +386,7 @@ func TestReproduceCondrieuPoAStemConflictWithAnotherStem(t *testing.T) {
 
 func TestGetTreeKeys(t *testing.T) {
 	addr := common.Hex2Bytes("71562b71999873DB5b286dF957af199Ec94617f7")
-	target := common.Hex2Bytes("0e19316be898a50719b7c321005583ddab6398f4e568d8efafb0619609700f00")
+	target := common.Hex2Bytes("e00f70099661b0afefd868e5f49863abdd83550021c3b71907a598e86b311900")
 	key := utils.GetTreeKeyVersion(addr)
 	t.Logf("key=%x", key)
 	t.Logf("actualKey=%x", target)