Implement MerkleCRH

sapling_merkle_tree.py

@@ -0,0 +1,9 @@
+#!/usr/bin/env python3
+from sapling_pedersen import pedersen_hash
+from sapling_utils import i2lebsp
+
+MERKLE_DEPTH = 32
+
+def merkle_crh(layer, left, right):
+    l = i2lebsp(6, MERKLE_DEPTH - 1 - layer)
+    return pedersen_hash(b'Zcash_PH', l + left + right)