From dfb10ab10fd793cdee0342c91931439f613b7289 Mon Sep 17 00:00:00 2001
From: Deirdre Connolly <deirdre@zfnd.org>
Date: Tue, 14 Jul 2020 05:04:45 -0400
Subject: [PATCH] Add NoteCommitment.extract_u()

---
 zebra-chain/src/notes/sapling.rs               | 9 +++++++++
 zebra-chain/src/transaction/tests/arbitrary.rs | 2 +-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/zebra-chain/src/notes/sapling.rs b/zebra-chain/src/notes/sapling.rs
index e78bab71..788033f4 100644
--- a/zebra-chain/src/notes/sapling.rs
+++ b/zebra-chain/src/notes/sapling.rs
@@ -109,6 +109,15 @@ impl ZcashDeserialize for NoteCommitment {
     }
 }
 
+impl NoteCommitment {
+    /// Hash Extractor for Jubjub (?)
+    ///
+    /// https://zips.z.cash/protocol/protocol.pdf#concreteextractorjubjub
+    pub fn extract_u(self) -> jubjub::Fq {
+        self.0.get_u()
+    }
+}
+
 /// The decrypted form of encrypted Sapling notes on the blockchain.
 pub struct NotePlaintext {
     diversifier: Diversifier,
diff --git a/zebra-chain/src/transaction/tests/arbitrary.rs b/zebra-chain/src/transaction/tests/arbitrary.rs
index e4aeef75..7aba6e3b 100644
--- a/zebra-chain/src/transaction/tests/arbitrary.rs
+++ b/zebra-chain/src/transaction/tests/arbitrary.rs
@@ -106,7 +106,7 @@ impl Arbitrary for Output {
             .prop_map(
                 |(cv, cm, ephemeral_key_bytes, enc_ciphertext, out_ciphertext, zkproof)| Self {
                     cv,
-                    cm_u: cm.0.get_u(),
+                    cm_u: cm.extract_u(),
                     ephemeral_key: jubjub::AffinePoint::from_bytes(ephemeral_key_bytes).unwrap(),
                     enc_ciphertext,
                     out_ciphertext,