NoteCommitments, renames, ValueCommitment, strategies, stub commit()

zebra-chain/src/keys/sprout.rs

@@ -176,6 +176,7 @@ impl From<SpendingKey> for ReceivingKey {
 
 /// Derived from a _SpendingKey_.
 #[derive(Copy, Clone, Eq, PartialEq)]
+#[cfg_attr(test, derive(proptest_derive::Arbitrary))]
 pub struct PayingKey(pub [u8; 32]);
 
 impl AsRef<[u8]> for PayingKey {

zebra-chain/src/notes/memo.rs

@@ -1,5 +1,8 @@
 use std::{cmp, convert::TryFrom, fmt};
 
+#[cfg(test)]
+use proptest::{arbitrary::Arbitrary, collection::vec, prelude::*};
+
 /// A 512-byte _Memo_ field associated with a note, as described in
 /// [protocol specification §5.5][ps].
 ///
@@ -48,6 +51,23 @@ impl fmt::Debug for Memo {
     }
 }
 
+#[cfg(test)]
+impl Arbitrary for Memo {
+    type Parameters = ();
+
+    fn arbitrary_with(_args: Self::Parameters) -> Self::Strategy {
+        (vec(any::<u8>(), 512))
+            .prop_map(|v| {
+                let mut bytes = [0; 512];
+                bytes.copy_from_slice(v.as_slice());
+                Memo(Box::new(bytes))
+            })
+            .boxed()
+    }
+
+    type Strategy = BoxedStrategy<Self>;
+}
+
 #[test]
 fn memo_fmt() {
     let memo = Memo(Box::new(

zebra-chain/src/notes/sapling.rs

@@ -1,4 +1,3 @@
-//!
 #![allow(clippy::unit_arg)]
 #![allow(dead_code)]
 
@@ -51,14 +50,33 @@ pub struct Note {
     diversifier: Diversifier,
     transmission_key: TransmissionKey,
     value: Amount<NonNegative>,
-    note_commitment_randomness: NoteCommitmentRandomness,
+    rcm: NoteCommitmentRandomness,
 }
 
+impl Note {
+    /// Construct a “windowed” Pedersen commitment by reusing a
+    /// Perderson hash constructon, and adding a randomized point on
+    /// the Jubjub curve.
+    ///
+    /// https://zips.z.cash/protocol/protocol.pdf#concretewindowedcommit
+    pub fn commit(&self) -> NoteCommitment {
+        // Windowed Pedersen Commitment
+
+        // NoteCommitment()
+        unimplemented!()
+    }
+}
+
+///
+#[derive(Clone, Copy, Debug)]
+//#[cfg_attr(test, derive(proptest_derive::Arbitrary))]
+pub struct NoteCommitment(jubjub::ExtendedPoint);
+
 /// The decrypted form of encrypted Sapling notes on the blockchain.
 pub struct NotePlaintext {
     diversifier: Diversifier,
     value: Amount<NonNegative>,
-    note_commitment_randomness: NoteCommitmentRandomness,
+    rcm: NoteCommitmentRandomness,
     memo: memo::Memo,
 }
 
@@ -190,6 +208,13 @@ impl Arbitrary for OutCiphertext {
     type Strategy = BoxedStrategy<Self>;
 }
 
+/// A Homomorphic Pedersen commitment to the value of a note, used in
+/// Spend and Output Descriptions.
+///
+/// https://zips.z.cash/protocol/protocol.pdf#concretehomomorphiccommit
+#[derive(Clone, Copy, Debug)]
+pub struct ValueCommitment(pub jubjub::ExtendedPoint);
+
 #[cfg(test)]
 proptest! {
 

zebra-chain/src/notes/sprout.rs

@@ -46,8 +46,9 @@ fn prf_nf(a_sk: [u8; 32], rho: [u8; 32]) -> [u8; 32] {
 /// Nullifier seed, named rho in the [spec][ps].
 ///
 /// [ps]: https://zips.z.cash/protocol/protocol.pdf#sproutkeycomponents
-#[derive(Clone, Copy)]
-struct NullifierSeed([u8; 32]);
+#[derive(Clone, Copy, Debug)]
+#[cfg_attr(test, derive(proptest_derive::Arbitrary))]
+pub struct NullifierSeed([u8; 32]);
 
 impl AsRef<[u8]> for NullifierSeed {
     fn as_ref(&self) -> &[u8] {
@@ -94,6 +95,7 @@ impl ZcashSerialize for Nullifier {
 
 /// The randomness used in the Pedersen Hash for note commitment.
 #[derive(Copy, Clone, Debug, PartialEq)]
+#[cfg_attr(test, derive(proptest_derive::Arbitrary))]
 pub struct NoteCommitmentRandomness(pub [u8; 32]);
 
 impl AsRef<[u8]> for NoteCommitmentRandomness {
@@ -102,39 +104,51 @@ impl AsRef<[u8]> for NoteCommitmentRandomness {
     }
 }
 
+///
+#[derive(Clone, Copy, Debug)]
+#[cfg_attr(test, derive(proptest_derive::Arbitrary))]
+pub struct NoteCommitment([u8; 32]);
+
 /// A Note represents that a value is spendable by the recipient who
 /// holds the spending key corresponding to a given shielded payment
 /// address.
+///
+/// https://zips.z.cash/protocol/protocol.pdf#notes
+#[derive(Clone, Copy, Debug)]
+#[cfg_attr(test, derive(proptest_derive::Arbitrary))]
 pub struct Note {
+    /// The paying key of the recipient’s shielded payment address
     paying_key: PayingKey,
+    /// An integer representing the value of the note in zatoshi (1 ZEC
+    /// = 10^8 zatoshi)
     value: Amount<NonNegative>,
-    nullifier_seed: NullifierSeed,
-    note_commitment_randomness: NoteCommitmentRandomness,
+    /// Input to PRF^nf to derive the nullifier of the note
+    rho: NullifierSeed,
+    /// A random commitment trapdoor
+    rcm: NoteCommitmentRandomness,
 }
 
 impl Note {
-    pub fn commitment(&self) -> NoteCommitment {
+    pub fn commit(&self) -> NoteCommitment {
         let leading_byte: u8 = 0xB0;
         let mut hasher = Sha256::default();
         hasher.input([leading_byte]);
         hasher.input(self.paying_key);
         hasher.input(self.value.to_bytes());
-        hasher.input(self.nullifier_seed);
-        hasher.input(self.note_commitment_randomness);
+        hasher.input(self.rho);
+        hasher.input(self.rcm);
 
         NoteCommitment(hasher.result().into())
     }
 }
 
-///
-pub struct NoteCommitment([u8; 32]);
-
 /// The decrypted form of encrypted Sprout notes on the blockchain.
+#[derive(Clone, Debug)]
+#[cfg_attr(test, derive(proptest_derive::Arbitrary))]
 pub struct NotePlaintext {
     value: Amount<NonNegative>,
-    // TODO: refine type
-    rho: [u8; 32],
-    note_commitment_randomness: NoteCommitmentRandomness,
+    rho: NullifierSeed,
+    rcm: NoteCommitmentRandomness,
     memo: Memo,
 }