From d33947b331a8600324e192fed0985a66b802a8b5 Mon Sep 17 00:00:00 2001
From: Deirdre Connolly <durumcrustulum@gmail.com>
Date: Tue, 20 Apr 2021 12:54:23 -0400
Subject: [PATCH] Impl FullViewingKey::from_spending_key(SpendingKey, Network)

Remove From impl
---
 zebra-chain/src/orchard/address.rs    |  3 ++-
 zebra-chain/src/orchard/keys.rs       | 31 +++++++++++++--------------
 zebra-chain/src/orchard/keys/tests.rs |  3 ++-
 3 files changed, 19 insertions(+), 18 deletions(-)

diff --git a/zebra-chain/src/orchard/address.rs b/zebra-chain/src/orchard/address.rs
index 146da338..2da7a5dc 100644
--- a/zebra-chain/src/orchard/address.rs
+++ b/zebra-chain/src/orchard/address.rs
@@ -66,7 +66,8 @@ mod tests {
 
         let spending_key = keys::SpendingKey::new(&mut OsRng);
 
-        let full_viewing_key = keys::FullViewingKey::from(spending_key);
+        let full_viewing_key =
+            keys::FullViewingKey::from_spending_key(spending_key, Network::Mainnet);
 
         // Default diversifier, where index = 0.
         let diversifier_key = keys::DiversifierKey::from(full_viewing_key);
diff --git a/zebra-chain/src/orchard/keys.rs b/zebra-chain/src/orchard/keys.rs
index 6ba99375..3db22478 100644
--- a/zebra-chain/src/orchard/keys.rs
+++ b/zebra-chain/src/orchard/keys.rs
@@ -568,8 +568,6 @@ pub struct FullViewingKey {
     ivk_commit_randomness: IvkCommitRandomness,
 }
 
-// TODO: impl a From that accepts a Network?
-
 impl fmt::Debug for FullViewingKey {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.debug_struct("FullViewingKey")
@@ -598,20 +596,6 @@ impl fmt::Display for FullViewingKey {
     }
 }
 
-impl From<SpendingKey> for FullViewingKey {
-    fn from(sk: SpendingKey) -> FullViewingKey {
-        let spend_authorizing_key = SpendAuthorizingKey::from(sk);
-
-        Self {
-            // TODO: handle setting the Network better.
-            network: Network::default(),
-            spend_validating_key: SpendValidatingKey::from(spend_authorizing_key),
-            nullifier_deriving_key: NullifierDerivingKey::from(sk),
-            ivk_commit_randomness: IvkCommitRandomness::from(sk),
-        }
-    }
-}
-
 impl FromStr for FullViewingKey {
     type Err = SerializationError;
 
@@ -657,6 +641,21 @@ impl FullViewingKey {
         // let R = PRF^expand_K( [0x82] || I2LEOSP256(ak) || I2LEOSP256(nk) )
         prf_expand(K, t)
     }
+
+    /// Derive a full viewing key from a existing spending key and its network.
+    ///
+    /// https://zips.z.cash/protocol/nu5.pdf#addressesandkeys
+    /// https://zips.z.cash/protocol/nu5.pdf#orchardfullviewingkeyencoding
+    pub fn from_spending_key(sk: SpendingKey, network: Network) -> FullViewingKey {
+        let spend_authorizing_key = SpendAuthorizingKey::from(sk);
+
+        Self {
+            network,
+            spend_validating_key: SpendValidatingKey::from(spend_authorizing_key),
+            nullifier_deriving_key: NullifierDerivingKey::from(sk),
+            ivk_commit_randomness: IvkCommitRandomness::from(sk),
+        }
+    }
 }
 
 /// An outgoing viewing key, as described in [protocol specification
diff --git a/zebra-chain/src/orchard/keys/tests.rs b/zebra-chain/src/orchard/keys/tests.rs
index c7f12fa4..8f8bd6cf 100644
--- a/zebra-chain/src/orchard/keys/tests.rs
+++ b/zebra-chain/src/orchard/keys/tests.rs
@@ -11,7 +11,8 @@ impl Arbitrary for TransmissionKey {
     fn arbitrary_with(_args: Self::Parameters) -> Self::Strategy {
         (any::<SpendingKey>())
             .prop_map(|spending_key| {
-                let full_viewing_key = FullViewingKey::from(spending_key);
+                let full_viewing_key =
+                    FullViewingKey::from_spending_key(spending_key, Network::Mainnet);
 
                 let diversifier_key = DiversifierKey::from(full_viewing_key);