From dd9c9ffa3fb65f99dcf2e05c3e6f06bd494b2c0d Mon Sep 17 00:00:00 2001
From: Jack Grigg <jack@z.cash>
Date: Wed, 30 Jan 2019 14:31:32 +0000
Subject: [PATCH] Add encodings for ExtendedSpendingKey and
 ExtendedFullViewingKey

---
 zcash_client_backend/src/constants/mainnet.rs | 16 +++++
 zcash_client_backend/src/constants/testnet.rs | 16 +++++
 zcash_client_backend/src/encoding.rs          | 59 ++++++++++++++++++-
 3 files changed, 90 insertions(+), 1 deletion(-)

diff --git a/zcash_client_backend/src/constants/mainnet.rs b/zcash_client_backend/src/constants/mainnet.rs
index 2850c456b..ed90697d0 100644
--- a/zcash_client_backend/src/constants/mainnet.rs
+++ b/zcash_client_backend/src/constants/mainnet.rs
@@ -3,6 +3,22 @@
 /// [SLIP 44]: https://github.com/satoshilabs/slips/blob/master/slip-0044.md
 pub const COIN_TYPE: u32 = 133;
 
+/// The HRP for a Bech32-encoded mainnet [`ExtendedSpendingKey`].
+///
+/// Defined in [ZIP 32].
+///
+/// [`ExtendedSpendingKey`]: zcash_primitives::zip32::ExtendedSpendingKey
+/// [ZIP 32]: https://github.com/zcash/zips/blob/master/zip-0032.rst
+pub const HRP_SAPLING_EXTENDED_SPENDING_KEY: &str = "secret-extended-key-main";
+
+/// The HRP for a Bech32-encoded mainnet [`ExtendedFullViewingKey`].
+///
+/// Defined in [ZIP 32].
+///
+/// [`ExtendedFullViewingKey`]: zcash_primitives::zip32::ExtendedFullViewingKey
+/// [ZIP 32]: https://github.com/zcash/zips/blob/master/zip-0032.rst
+pub const HRP_SAPLING_EXTENDED_FULL_VIEWING_KEY: &str = "zxviews";
+
 /// The HRP for a Bech32-encoded mainnet [`PaymentAddress`].
 ///
 /// Defined in section 5.6.4 of the [Zcash Protocol Specification].
diff --git a/zcash_client_backend/src/constants/testnet.rs b/zcash_client_backend/src/constants/testnet.rs
index f4ea3c2a0..f151110e2 100644
--- a/zcash_client_backend/src/constants/testnet.rs
+++ b/zcash_client_backend/src/constants/testnet.rs
@@ -3,6 +3,22 @@
 /// [SLIP 44]: https://github.com/satoshilabs/slips/blob/master/slip-0044.md
 pub const COIN_TYPE: u32 = 1;
 
+/// The HRP for a Bech32-encoded testnet [`ExtendedSpendingKey`].
+///
+/// Defined in [ZIP 32].
+///
+/// [`ExtendedSpendingKey`]: zcash_primitives::zip32::ExtendedSpendingKey
+/// [ZIP 32]: https://github.com/zcash/zips/blob/master/zip-0032.rst
+pub const HRP_SAPLING_EXTENDED_SPENDING_KEY: &str = "secret-extended-key-test";
+
+/// The HRP for a Bech32-encoded testnet [`ExtendedFullViewingKey`].
+///
+/// Defined in [ZIP 32].
+///
+/// [`ExtendedFullViewingKey`]: zcash_primitives::zip32::ExtendedFullViewingKey
+/// [ZIP 32]: https://github.com/zcash/zips/blob/master/zip-0032.rst
+pub const HRP_SAPLING_EXTENDED_FULL_VIEWING_KEY: &str = "zxviewtestsapling";
+
 /// The HRP for a Bech32-encoded testnet [`PaymentAddress`].
 ///
 /// Defined in section 5.6.4 of the [Zcash Protocol Specification].
diff --git a/zcash_client_backend/src/encoding.rs b/zcash_client_backend/src/encoding.rs
index 7150621e0..3a201ad39 100644
--- a/zcash_client_backend/src/encoding.rs
+++ b/zcash_client_backend/src/encoding.rs
@@ -10,7 +10,10 @@ use sapling_crypto::{
     primitives::{Diversifier, PaymentAddress},
 };
 use std::io::{self, Write};
-use zcash_primitives::JUBJUB;
+use zcash_primitives::{
+    zip32::{ExtendedFullViewingKey, ExtendedSpendingKey},
+    JUBJUB,
+};
 
 fn bech32_encode<F>(hrp: &str, write: F) -> String
 where
@@ -38,6 +41,60 @@ where
     }
 }
 
+/// Writes an [`ExtendedSpendingKey`] as a Bech32-encoded string.
+///
+/// # Examples
+///
+/// ```
+/// use zcash_client_backend::{
+///     constants::testnet::{COIN_TYPE, HRP_SAPLING_EXTENDED_SPENDING_KEY},
+///     encoding::encode_extended_spending_key,
+///     keys::spending_key,
+/// };
+///
+/// let extsk = spending_key(&[0; 32][..], COIN_TYPE, 0);
+/// let encoded = encode_extended_spending_key(HRP_SAPLING_EXTENDED_SPENDING_KEY, &extsk);
+/// ```
+pub fn encode_extended_spending_key(hrp: &str, extsk: &ExtendedSpendingKey) -> String {
+    bech32_encode(hrp, |w| extsk.write(w))
+}
+
+/// Decodes an [`ExtendedSpendingKey`] from a Bech32-encoded string.
+pub fn decode_extended_spending_key(
+    hrp: &str,
+    s: &str,
+) -> Result<Option<ExtendedSpendingKey>, Error> {
+    bech32_decode(hrp, s, |data| ExtendedSpendingKey::read(&data[..]).ok())
+}
+
+/// Writes an [`ExtendedFullViewingKey`] as a Bech32-encoded string.
+///
+/// # Examples
+///
+/// ```
+/// use zcash_client_backend::{
+///     constants::testnet::{COIN_TYPE, HRP_SAPLING_EXTENDED_FULL_VIEWING_KEY},
+///     encoding::encode_extended_full_viewing_key,
+///     keys::spending_key,
+/// };
+/// use zcash_primitives::zip32::ExtendedFullViewingKey;
+///
+/// let extsk = spending_key(&[0; 32][..], COIN_TYPE, 0);
+/// let extfvk = ExtendedFullViewingKey::from(&extsk);
+/// let encoded = encode_extended_full_viewing_key(HRP_SAPLING_EXTENDED_FULL_VIEWING_KEY, &extfvk);
+/// ```
+pub fn encode_extended_full_viewing_key(hrp: &str, extfvk: &ExtendedFullViewingKey) -> String {
+    bech32_encode(hrp, |w| extfvk.write(w))
+}
+
+/// Decodes an [`ExtendedFullViewingKey`] from a Bech32-encoded string.
+pub fn decode_extended_full_viewing_key(
+    hrp: &str,
+    s: &str,
+) -> Result<Option<ExtendedFullViewingKey>, Error> {
+    bech32_decode(hrp, s, |data| ExtendedFullViewingKey::read(&data[..]).ok())
+}
+
 /// Writes a [`PaymentAddress`] as a Bech32-encoded string.
 ///
 /// # Examples