Add Orchard MerkleCRH

orchard_merkle_tree.py

@@ -0,0 +1,32 @@
+#!/usr/bin/env python3
+import sys; assert sys.version_info[0] >= 3, "Python 3 required."
+
+from binascii import unhexlify
+
+from orchard_pallas import Fp
+from orchard_sinsemilla import sinsemilla_hash
+
+from sapling_utils import i2lebsp, leos2bsp
+
+# https://zips.z.cash/protocol/nu5.pdf#constants
+MERKLE_DEPTH = 32
+L_MERKLE = 255
+
+# https://zips.z.cash/protocol/nu5.pdf#orchardmerklecrh
+def merkle_crh(layer, left, right):
+    assert layer < MERKLE_DEPTH
+    assert len(left) == L_MERKLE
+    assert len(right) == L_MERKLE
+    l = i2lebsp(6, MERKLE_DEPTH - 1 - layer)
+    return sinsemilla_hash(b"z.cash:Orchard-MerkleCRH", l + left + right)
+
+left = unhexlify("87a086ae7d2252d58729b30263fb7b66308bf94ef59a76c9c86e7ea016536505")[::-1]
+right = unhexlify("a75b84a125b2353da7e8d96ee2a15efe4de23df9601b9d9564ba59de57130406")[::-1]
+
+left = leos2bsp(left)[:L_MERKLE]
+right = leos2bsp(right)[:L_MERKLE]
+
+# parent = merkle_crh(MERKLE_DEPTH - 1 - 25, left, right)
+parent = Fp(17261766847362299889572407272882432634088514578301422827180452043349931590033)
+assert merkle_crh(MERKLE_DEPTH - 1 - 25, left, right) == parent
+assert merkle_crh(MERKLE_DEPTH - 1 - 26, left, right) != parent