Add raw address serialization and parsing.

src/address.rs

@@ -1,3 +1,7 @@
+use std::convert::TryInto;
+
+use subtle::CtOption;
+
 use crate::{
     keys::{DiversifiedTransmissionKey, Diversifier},
     spec::{diversify_hash, NonIdentityPallasPoint},
@@ -39,6 +43,24 @@ impl Address {
     pub(crate) fn pk_d(&self) -> &DiversifiedTransmissionKey {
         &self.pk_d
     }
+
+    /// Serialize this address to its "raw" encoding as defined in
+    /// https://zips.z.cash/protocol/protocol.pdf#orchardpaymentaddrencoding
+    pub fn to_raw_address_bytes(&self) -> [u8; 43] {
+        let mut result = [0u8; 43];
+        result[..11].copy_from_slice(self.d.as_array());
+        result[11..].copy_from_slice(&self.pk_d.to_bytes());
+        result
+    }
+
+    /// Parse an address from its "raw" encoding as defined in 
+    /// https://zips.z.cash/protocol/protocol.pdf#orchardpaymentaddrencoding
+    pub fn from_raw_address_bytes(bytes: &[u8; 43]) -> CtOption<Self> {
+        DiversifiedTransmissionKey::from_bytes(bytes[11..].try_into().unwrap()).map(|pk_d| {
+            let d = Diversifier::from_bytes(bytes[..11].try_into().unwrap());
+            Self::from_parts(d, pk_d)
+        })
+    }
 }
 
 /// Generators for property testing.

src/keys.rs

@@ -10,8 +10,7 @@ use group::{prime::PrimeCurveAffine, Curve, GroupEncoding};
 use halo2::arithmetic::FieldExt;
 use pasta_curves::pallas;
 use rand::RngCore;
-use subtle::ConstantTimeEq;
-use subtle::CtOption;
+use subtle::{Choice, ConditionallySelectable, ConstantTimeEq, CtOption};
 use zcash_note_encryption::EphemeralKeyBytes;
 
 use crate::{
@@ -510,6 +509,20 @@ impl DiversifiedTransmissionKey {
     }
 }
 
+impl Default for DiversifiedTransmissionKey {
+    fn default() -> Self {
+        DiversifiedTransmissionKey(NonIdentityPallasPoint::default())
+    }
+}
+
+impl ConditionallySelectable for DiversifiedTransmissionKey {
+    fn conditional_select(a: &Self, b: &Self, choice: Choice) -> Self {
+        DiversifiedTransmissionKey(NonIdentityPallasPoint::conditional_select(
+            &a.0, &b.0, choice,
+        ))
+    }
+}
+
 /// An ephemeral secret key used to encrypt an output note on-chain.
 ///
 /// `esk` is "ephemeral" in the sense that each secret key is only used once. In