Merge pull request #502 from rikitau/bip32-example

Add an example for bip32 key derivation

examples/bip32.rs

@@ -0,0 +1,61 @@
+extern crate bitcoin;
+
+use std::{env, process};
+use std::str::FromStr;
+
+use bitcoin::secp256k1::Secp256k1;
+use bitcoin::util::key::PrivateKey;
+use bitcoin::util::bip32::ExtendedPrivKey;
+use bitcoin::util::bip32::ExtendedPubKey;
+use bitcoin::util::bip32::DerivationPath;
+use bitcoin::util::bip32::ChildNumber;
+use bitcoin::util::address::Address;
+
+fn main() {
+    // This example derives root xprv
+    // from a 32-byte secret of the input WIF string,
+    // derives the child xprv with path m/84h/0h/0h,
+    // prints out corresponding xpub,
+    // calculates and prints out the first receiving segwit address.
+    // Run this example with cargo and WIF argument:
+    // cargo run --example bip32 L1HKVVLHXiUhecWnwFYF6L3shkf1E12HUmuZTESvBXUdx3yqVP1D
+
+    let args: Vec<String> = env::args().collect();
+    if args.len() < 2 {
+        eprintln!("not enough arguments. usage: {} <WIF>", &args[0]);
+        process::exit(1);
+    }
+
+    let wif = PrivateKey::from_wif(&args[1]).unwrap();
+    println!("Seed WIF: {}", wif);
+
+    // use the network from WIF key
+    let network = wif.network;
+    println!("Network: {:?}", network);
+    // seed is a 32-byte secret in WIF
+    let seed = wif.to_bytes();
+
+    // we need secp256k1 context for key derivation
+    let secp = Secp256k1::new();
+
+    // calculate root key from seed
+    let root = ExtendedPrivKey::new_master(network, &seed).unwrap();
+    println!("Root key: {}", root);
+
+    // derive child xpub
+    let path = DerivationPath::from_str("m/84h/0h/0h").unwrap();
+    let child = root.derive_priv(&secp, &path).unwrap();
+    println!("Child at {}: {}", path, child);
+    let xpub = ExtendedPubKey::from_private(&secp, &child);
+    println!("Public key at {}: {}", path, xpub);
+
+    // generate first receiving address at m/0/0
+    // manually creating indexes this time
+    let zero = ChildNumber::from_normal_idx(0).unwrap();
+    let public_key = xpub.derive_pub(&secp, &vec![zero, zero])
+                         .unwrap()
+                         .public_key;
+    let address = Address::p2wpkh(&public_key, network).unwrap();
+    println!("First receiving address: {}", address);
+
+}