Merge pull request #325 from str4d/example-diversify-address

zcash_client_backend: Add example to generate diversified addresses

zcash_client_backend/Cargo.toml

@@ -31,6 +31,7 @@ percent-encoding = "2.1.0"
 protobuf-codegen-pure = "2.15"
 
 [dev-dependencies]
+gumdrop = "0.8"
 rand_core = "0.5.1"
 rand_xorshift = "0.2"
 

zcash_client_backend/examples/diversify-address.rs

@@ -0,0 +1,87 @@
+use std::convert::TryInto;
+
+use gumdrop::Options;
+use zcash_client_backend::encoding::{decode_extended_full_viewing_key, encode_payment_address};
+use zcash_primitives::{
+    constants::{mainnet, testnet},
+    zip32::{DiversifierIndex, ExtendedFullViewingKey},
+};
+
+fn parse_viewing_key(s: &str) -> Result<(ExtendedFullViewingKey, bool), &'static str> {
+    decode_extended_full_viewing_key(mainnet::HRP_SAPLING_EXTENDED_FULL_VIEWING_KEY, s)
+        .map(|res| {
+            res.map(|vk| (vk, true))
+                .ok_or("Invalid mainnet Sapling viewing key")
+        })
+        .or_else(|_| {
+            decode_extended_full_viewing_key(testnet::HRP_SAPLING_EXTENDED_FULL_VIEWING_KEY, s).map(
+                |res| {
+                    res.map(|vk| (vk, false))
+                        .ok_or("Invalid testnet Sapling viewing key")
+                },
+            )
+        })
+        .map_err(|_| "Invalid Sapling viewing key")?
+}
+
+fn parse_diversifier_index(s: &str) -> Result<DiversifierIndex, &'static str> {
+    let i: u128 = s.parse().map_err(|_| "Diversifier index is not a number")?;
+    if i >= (1 << 88) {
+        return Err("Diversifier index too large");
+    }
+    Ok(DiversifierIndex(i.to_le_bytes()[..11].try_into().unwrap()))
+}
+
+fn encode_diversifier_index(di: &DiversifierIndex) -> u128 {
+    let mut bytes = [0; 16];
+    bytes[..11].copy_from_slice(&di.0);
+    u128::from_le_bytes(bytes)
+}
+
+#[derive(Debug, Options)]
+struct MyOptions {
+    #[options(help = "Print this help message and exit.")]
+    help: bool,
+
+    #[options(
+        free,
+        help = "The Sapling viewing key to generate diversified addresses from",
+        parse(try_from_str = "parse_viewing_key")
+    )]
+    viewing_key: Option<(ExtendedFullViewingKey, bool)>,
+
+    #[options(
+        free,
+        help = "The index of the diversified address to generate (default 0). Some indices don't have a corresponding address.",
+        parse(try_from_str = "parse_diversifier_index")
+    )]
+    diversifier_index: DiversifierIndex,
+}
+
+fn main() {
+    let opts = MyOptions::parse_args_default_or_exit();
+
+    let (extfvk, is_mainnet) = if let Some(res) = opts.viewing_key {
+        res
+    } else {
+        eprintln!("Missing Sapling viewing key");
+        return;
+    };
+
+    let (diversifier_index, address) = extfvk.address(opts.diversifier_index).unwrap();
+    println!(
+        "# Diversifier index: {}",
+        encode_diversifier_index(&diversifier_index)
+    );
+    println!(
+        "{}",
+        encode_payment_address(
+            if is_mainnet {
+                mainnet::HRP_SAPLING_PAYMENT_ADDRESS
+            } else {
+                testnet::HRP_SAPLING_PAYMENT_ADDRESS
+            },
+            &address
+        )
+    );
+}