BIP32 Lib Integration (#1454)

* Test integrating BIP-32 implementation (not complete) * Test integrating BIP-32 implementation (not complete) * factor out bip32 crypto functions into trait * rustfmt * compliation * rustfmt * fixes for test vectors.. all work now with hashes specified in BIP32 * rustfmt * move reference hasher out of test
2025-01-20 19:11:08 +03:00 · 2018-09-04 10:58:26 +01:00 · 2018-09-04 10:58:26 +01:00 · 63880f71c7
commit 63880f71c7
parent ed73db671f
9 changed files with 1553 additions and 17 deletions
--- a/Cargo.lock
+++ b/Cargo.lock
@ -713,6 +713,7 @@ dependencies = [
 "byteorder 1.2.4 (registry+https://github.com/rust-lang/crates.io-index)",
 "grin_util 0.3.0",
 "rand 0.3.22 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rust-crypto 0.2.36 (registry+https://github.com/rust-lang/crates.io-index)",
 "serde 1.0.70 (registry+https://github.com/rust-lang/crates.io-index)",
 "serde_derive 1.0.70 (registry+https://github.com/rust-lang/crates.io-index)",
 "serde_json 1.0.24 (registry+https://github.com/rust-lang/crates.io-index)",
@ -1717,6 +1718,18 @@ dependencies = [
 "url 1.7.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]

+[[package]]
+name = "rust-crypto"
+version = "0.2.36"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "gcc 0.3.54 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.42 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand 0.3.22 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rustc-serialize 0.3.24 (registry+https://github.com/rust-lang/crates.io-index)",
+ "time 0.1.40 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "rustc-demangle"
 version = "0.1.9"
@ -2629,6 +2642,7 @@ dependencies = [
 "checksum relay 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "1576e382688d7e9deecea24417e350d3062d97e32e45d70b1cde65994ff1489a"
 "checksum remove_dir_all 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "3488ba1b9a2084d38645c4c08276a1752dcbf2c7130d74f1569681ad5d2799c5"
 "checksum reqwest 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)" = "5866613d84e2a39c0479a960bf2d0eff1fbfc934f02cd42b5c08c1e1efc5b1fd"
+"checksum rust-crypto 0.2.36 (registry+https://github.com/rust-lang/crates.io-index)" = "f76d05d3993fd5f4af9434e8e436db163a12a9d40e1a58a726f27a01dfd12a2a"
 "checksum rustc-demangle 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)" = "bcfe5b13211b4d78e5c2cadfebd7769197d95c639c35a50057eb4c05de811395"
 "checksum rustc-serialize 0.3.24 (registry+https://github.com/rust-lang/crates.io-index)" = "dcf128d1287d2ea9d80910b5f1120d0b8eede3fbf1abe91c40d39ea7d51e6fda"
 "checksum safemem 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "e27a8b19b835f7aea908818e871f5cc3a5a186550c30773be987e155e8163d8f"
--- a/keychain/Cargo.toml
+++ b/keychain/Cargo.toml
@ -14,5 +14,7 @@ serde = "1"
 serde_derive = "1"
 serde_json = "1"
 uuid = { version = "0.6", features = ["serde", "v4"] }
+#only used for hashing
+rust-crypto = "0.2"

 grin_util = { path = "../util" }
--- a/keychain/src/base58.rs
+++ b/keychain/src/base58.rs
@ -0,0 +1,428 @@
+// Copyright 2018 The Grin Developers
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Rust Bitcoin Library
+// Written in 2014 by
+//   Andrew Poelstra <apoelstra@wpsoftware.net>
+//
+// To the extent possible under law, the author(s) have dedicated all
+// copyright and related and neighboring rights to this software to
+// the public domain worldwide. This software is distributed without
+// any warranty.
+//
+// You should have received a copy of the CC0 Public Domain Dedication
+// along with this software.
+// If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
+//
+
+//! Base58 encoder and decoder
+
+use std::{error, fmt, mem, str};
+
+use byteorder::{ByteOrder, LittleEndian};
+use crypto::digest::Digest;
+use crypto::sha2::Sha256;
+
+/// Sha256dHash
+fn sha256d_hash(data: &[u8]) -> [u8; 32] {
+	let mut ret = [0; 32];
+	let mut sha2 = Sha256::new();
+	sha2.input(data);
+	sha2.result(&mut ret);
+	sha2.reset();
+	sha2.input(&ret);
+	sha2.result(&mut ret);
+	ret
+}
+
+#[inline]
+pub fn into_le_low_u32(data: [u8; 32]) -> u32 {
+	let mut ret: [u64; 4] = unsafe { mem::transmute(data) };
+	for x in (&mut ret).iter_mut() {
+		*x = x.to_le();
+	}
+	ret[0] as u32
+}
+
+/// An error that might occur during base58 decoding
+#[derive(Debug, PartialEq, Eq, Clone)]
+pub enum Error {
+	/// Invalid character encountered
+	BadByte(u8),
+	/// Checksum was not correct (expected, actual)
+	BadChecksum(u32, u32),
+	/// The length (in bytes) of the object was not correct
+	/// Note that if the length is excessively long the provided length may be
+	/// an estimate (and the checksum step may be skipped).
+	InvalidLength(usize),
+	/// Version byte(s) were not recognized
+	InvalidVersion(Vec<u8>),
+	/// Checked data was less than 4 bytes
+	TooShort(usize),
+	/// Any other error
+	Other(String),
+}
+
+impl fmt::Display for Error {
+	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+		match *self {
+			Error::BadByte(b) => write!(f, "invalid base58 character 0x{:x}", b),
+			Error::BadChecksum(exp, actual) => write!(
+				f,
+				"base58ck checksum 0x{:x} does not match expected 0x{:x}",
+				actual, exp
+			),
+			Error::InvalidLength(ell) => write!(f, "length {} invalid for this base58 type", ell),
+			Error::InvalidVersion(ref v) => {
+				write!(f, "version {:?} invalid for this base58 type", v)
+			}
+			Error::TooShort(_) => write!(f, "base58ck data not even long enough for a checksum"),
+			Error::Other(ref s) => f.write_str(s),
+		}
+	}
+}
+
+impl error::Error for Error {
+	fn cause(&self) -> Option<&error::Error> {
+		None
+	}
+	fn description(&self) -> &'static str {
+		match *self {
+			Error::BadByte(_) => "invalid b58 character",
+			Error::BadChecksum(_, _) => "invalid b58ck checksum",
+			Error::InvalidLength(_) => "invalid length for b58 type",
+			Error::InvalidVersion(_) => "invalid version for b58 type",
+			Error::TooShort(_) => "b58ck data less than 4 bytes",
+			Error::Other(_) => "unknown b58 error",
+		}
+	}
+}
+
+static BASE58_CHARS: &'static [u8] = b"123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
+
+static BASE58_DIGITS: [Option<u8>; 128] = [
+	None,
+	None,
+	None,
+	None,
+	None,
+	None,
+	None,
+	None, // 0-7
+	None,
+	None,
+	None,
+	None,
+	None,
+	None,
+	None,
+	None, // 8-15
+	None,
+	None,
+	None,
+	None,
+	None,
+	None,
+	None,
+	None, // 16-23
+	None,
+	None,
+	None,
+	None,
+	None,
+	None,
+	None,
+	None, // 24-31
+	None,
+	None,
+	None,
+	None,
+	None,
+	None,
+	None,
+	None, // 32-39
+	None,
+	None,
+	None,
+	None,
+	None,
+	None,
+	None,
+	None, // 40-47
+	None,
+	Some(0),
+	Some(1),
+	Some(2),
+	Some(3),
+	Some(4),
+	Some(5),
+	Some(6), // 48-55
+	Some(7),
+	Some(8),
+	None,
+	None,
+	None,
+	None,
+	None,
+	None, // 56-63
+	None,
+	Some(9),
+	Some(10),
+	Some(11),
+	Some(12),
+	Some(13),
+	Some(14),
+	Some(15), // 64-71
+	Some(16),
+	None,
+	Some(17),
+	Some(18),
+	Some(19),
+	Some(20),
+	Some(21),
+	None, // 72-79
+	Some(22),
+	Some(23),
+	Some(24),
+	Some(25),
+	Some(26),
+	Some(27),
+	Some(28),
+	Some(29), // 80-87
+	Some(30),
+	Some(31),
+	Some(32),
+	None,
+	None,
+	None,
+	None,
+	None, // 88-95
+	None,
+	Some(33),
+	Some(34),
+	Some(35),
+	Some(36),
+	Some(37),
+	Some(38),
+	Some(39), // 96-103
+	Some(40),
+	Some(41),
+	Some(42),
+	Some(43),
+	None,
+	Some(44),
+	Some(45),
+	Some(46), // 104-111
+	Some(47),
+	Some(48),
+	Some(49),
+	Some(50),
+	Some(51),
+	Some(52),
+	Some(53),
+	Some(54), // 112-119
+	Some(55),
+	Some(56),
+	Some(57),
+	None,
+	None,
+	None,
+	None,
+	None, // 120-127
+];
+
+/// Decode base58-encoded string into a byte vector
+pub fn from(data: &str) -> Result<Vec<u8>, Error> {
+	// 11/15 is just over log_256(58)
+	let mut scratch = vec![0u8; 1 + data.len() * 11 / 15];
+	// Build in base 256
+	for d58 in data.bytes() {
+		// Compute "X = X * 58 + next_digit" in base 256
+		if d58 as usize > BASE58_DIGITS.len() {
+			return Err(Error::BadByte(d58));
+		}
+		let mut carry = match BASE58_DIGITS[d58 as usize] {
+			Some(d58) => d58 as u32,
+			None => {
+				return Err(Error::BadByte(d58));
+			}
+		};
+		for d256 in scratch.iter_mut().rev() {
+			carry += *d256 as u32 * 58;
+			*d256 = carry as u8;
+			carry /= 256;
+		}
+		assert_eq!(carry, 0);
+	}
+
+	// Copy leading zeroes directly
+	let mut ret: Vec<u8> = data
+		.bytes()
+		.take_while(|&x| x == BASE58_CHARS[0])
+		.map(|_| 0)
+		.collect();
+	// Copy rest of string
+	ret.extend(scratch.into_iter().skip_while(|&x| x == 0));
+	Ok(ret)
+}
+
+/// Decode a base58check-encoded string
+pub fn from_check(data: &str) -> Result<Vec<u8>, Error> {
+	let mut ret: Vec<u8> = from(data)?;
+	if ret.len() < 4 {
+		return Err(Error::TooShort(ret.len()));
+	}
+	let ck_start = ret.len() - 4;
+	let expected = sha256d_hash(&ret[..ck_start]);
+	let expected = into_le_low_u32(expected);
+	let actual = LittleEndian::read_u32(&ret[ck_start..(ck_start + 4)]);
+	if expected != actual {
+		return Err(Error::BadChecksum(expected, actual));
+	}
+
+	ret.truncate(ck_start);
+	Ok(ret)
+}
+
+fn encode_iter_utf8<I>(data: I) -> Vec<u8>
+where
+	I: Iterator<Item = u8> + Clone,
+{
+	let (len, _) = data.size_hint();
+
+	// 7/5 is just over log_58(256)
+	let mut ret = Vec::with_capacity(1 + len * 7 / 5);
+
+	let mut leading_zero_count = 0;
+	let mut leading_zeroes = true;
+	// Build string in little endian with 0-58 in place of characters...
+	for d256 in data {
+		let mut carry = d256 as usize;
+		if leading_zeroes && carry == 0 {
+			leading_zero_count += 1;
+		} else {
+			leading_zeroes = false;
+		}
+
+		for ch in ret.iter_mut() {
+			let new_ch = *ch as usize * 256 + carry;
+			*ch = (new_ch % 58) as u8;
+			carry = new_ch / 58;
+		}
+		while carry > 0 {
+			ret.push((carry % 58) as u8);
+			carry /= 58;
+		}
+	}
+
+	// ... then reverse it and convert to chars
+	for _ in 0..leading_zero_count {
+		ret.push(0);
+	}
+	ret.reverse();
+	for ch in ret.iter_mut() {
+		*ch = BASE58_CHARS[*ch as usize];
+	}
+	ret
+}
+
+fn encode_iter<I>(data: I) -> String
+where
+	I: Iterator<Item = u8> + Clone,
+{
+	let ret = encode_iter_utf8(data);
+	String::from_utf8(ret).unwrap()
+}
+
+/// Directly encode a slice as base58 into a `Formatter`.
+fn _encode_iter_to_fmt<I>(fmt: &mut fmt::Formatter, data: I) -> fmt::Result
+where
+	I: Iterator<Item = u8> + Clone,
+{
+	let ret = encode_iter_utf8(data);
+	fmt.write_str(str::from_utf8(&ret).unwrap())
+}
+
+/// Directly encode a slice as base58
+pub fn _encode_slice(data: &[u8]) -> String {
+	encode_iter(data.iter().cloned())
+}
+
+/// Obtain a string with the base58check encoding of a slice
+/// (Tack the first 4 256-digits of the object's Bitcoin hash onto the end.)
+pub fn check_encode_slice(data: &[u8]) -> String {
+	let checksum = sha256d_hash(&data);
+	encode_iter(data.iter().cloned().chain(checksum[0..4].iter().cloned()))
+}
+
+/// Obtain a string with the base58check encoding of a slice
+/// (Tack the first 4 256-digits of the object's Bitcoin hash onto the end.)
+pub fn _check_encode_slice_to_fmt(fmt: &mut fmt::Formatter, data: &[u8]) -> fmt::Result {
+	let checksum = sha256d_hash(&data);
+	let iter = data.iter().cloned().chain(checksum[0..4].iter().cloned());
+	_encode_iter_to_fmt(fmt, iter)
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use util::from_hex;
+
+	#[test]
+	fn test_base58_encode() {
+		// Basics
+		assert_eq!(&_encode_slice(&[0][..]), "1");
+		assert_eq!(&_encode_slice(&[1][..]), "2");
+		assert_eq!(&_encode_slice(&[58][..]), "21");
+		assert_eq!(&_encode_slice(&[13, 36][..]), "211");
+
+		// Leading zeroes
+		assert_eq!(&_encode_slice(&[0, 13, 36][..]), "1211");
+		assert_eq!(&_encode_slice(&[0, 0, 0, 0, 13, 36][..]), "1111211");
+
+		// Addresses
+		let addr = from_hex("00f8917303bfa8ef24f292e8fa1419b20460ba064d".to_owned()).unwrap();
+		assert_eq!(
+			&check_encode_slice(&addr[..]),
+			"1PfJpZsjreyVrqeoAfabrRwwjQyoSQMmHH"
+		);
+	}
+
+	#[test]
+	fn test_base58_decode() {
+		// Basics
+		assert_eq!(from("1").ok(), Some(vec![0u8]));
+		assert_eq!(from("2").ok(), Some(vec![1u8]));
+		assert_eq!(from("21").ok(), Some(vec![58u8]));
+		assert_eq!(from("211").ok(), Some(vec![13u8, 36]));
+
+		// Leading zeroes
+		assert_eq!(from("1211").ok(), Some(vec![0u8, 13, 36]));
+		assert_eq!(from("111211").ok(), Some(vec![0u8, 0, 0, 13, 36]));
+
+		// Addresses
+		assert_eq!(
+			from_check("1PfJpZsjreyVrqeoAfabrRwwjQyoSQMmHH").ok(),
+			Some(from_hex("00f8917303bfa8ef24f292e8fa1419b20460ba064d".to_owned()).unwrap())
+		)
+	}
+
+	#[test]
+	fn test_base58_roundtrip() {
+		let s = "xprv9wTYmMFdV23N2TdNG573QoEsfRrWKQgWeibmLntzniatZvR9BmLnvSxqu53Kw1UmYPxLgboyZQaXwTCg8MSY3H2EU4pWcQDnRnrVA1xe8fs";
+		let v: Vec<u8> = from_check(s).unwrap();
+		assert_eq!(check_encode_slice(&v[..]), s);
+		assert_eq!(from_check(&check_encode_slice(&v[..])).ok(), Some(v));
+	}
+}
--- a/keychain/src/extkey.rs
+++ b/keychain/src/extkey.rs
@ -15,8 +15,8 @@
 use blake2::blake2b::blake2b;
 use byteorder::{BigEndian, ByteOrder};
 use types::{Error, Identifier};
-use util::secp::Secp256k1;
 use util::secp::key::SecretKey;
+use util::secp::Secp256k1;

 #[derive(Debug, Clone)]
 pub struct ChildKey {
@ -119,8 +119,8 @@ mod test {

 	use super::{ExtendedKey, Identifier};
 	use util;
-	use util::secp::Secp256k1;
 	use util::secp::key::SecretKey;
+	use util::secp::Secp256k1;

 	fn from_hex(hex_str: &str) -> Vec<u8> {
 		util::from_hex(hex_str.to_string()).unwrap()
--- a/keychain/src/extkey_bip32.rs
+++ b/keychain/src/extkey_bip32.rs
@ -0,0 +1,818 @@
+// Copyright 2018 The Grin Developers
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Rust Bitcoin Library
+// Written in 2014 by
+//     Andrew Poelstra <apoelstra@wpsoftware.net>
+// To the extent possible under law, the author(s) have dedicated all
+// copyright and related and neighboring rights to this software to
+// the public domain worldwide. This software is distributed without
+// any warranty.
+//
+// You should have received a copy of the CC0 Public Domain Dedication
+// along with this software.
+// If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
+//
+
+//! Implementation of BIP32 hierarchical deterministic wallets, as defined
+//! at https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki
+//! Modified from above to integrate into grin and allow for different
+//! hashing algorithms if desired
+
+#[cfg(feature = "serde")]
+use serde;
+use std::default::Default;
+use std::io::Cursor;
+use std::str::FromStr;
+use std::{error, fmt};
+
+use byteorder::{BigEndian, ByteOrder, ReadBytesExt};
+use util::secp::key::{PublicKey, SecretKey};
+use util::secp::{self, ContextFlag, Secp256k1};
+
+use crypto::digest::Digest;
+use crypto::hmac::Hmac;
+use crypto::mac::Mac;
+use crypto::ripemd160::Ripemd160;
+use crypto::sha2::{Sha256, Sha512};
+
+use base58;
+
+/// A chain code
+pub struct ChainCode([u8; 32]);
+impl_array_newtype!(ChainCode, u8, 32);
+impl_array_newtype_show!(ChainCode);
+impl_array_newtype_encodable!(ChainCode, u8, 32);
+
+/// A fingerprint
+pub struct Fingerprint([u8; 4]);
+impl_array_newtype!(Fingerprint, u8, 4);
+impl_array_newtype_show!(Fingerprint);
+impl_array_newtype_encodable!(Fingerprint, u8, 4);
+
+impl Default for Fingerprint {
+	fn default() -> Fingerprint {
+		Fingerprint([0, 0, 0, 0])
+	}
+}
+
+/// Allow different implementations of hash functions used in BIP32 Derivations
+/// Grin uses blake2 everywhere but the spec calls for SHA512/Ripemd160, so allow
+/// this in future and allow us to unit test against published BIP32 test vectors
+/// The function names refer to the place of the hash in the reference BIP32 spec,
+/// not what the actual implementation is
+
+pub trait BIP32Hasher {
+	fn network_priv() -> [u8; 4];
+	fn network_pub() -> [u8; 4];
+	fn master_seed() -> [u8; 12];
+	fn init_sha512(&mut self, seed: &[u8]);
+	fn append_sha512(&mut self, value: &[u8]);
+	fn result_sha512(&mut self) -> [u8; 64];
+	fn sha_256(&self, input: &[u8]) -> [u8; 32];
+	fn ripemd_160(&self, input: &[u8]) -> [u8; 20];
+}
+
+/// Implementation of the above that uses the standard BIP32 Hash algorithms
+pub struct BIP32ReferenceHasher {
+	hmac_sha512: Hmac<Sha512>,
+}
+
+impl BIP32ReferenceHasher {
+	/// New empty hasher
+	pub fn new() -> BIP32ReferenceHasher {
+		BIP32ReferenceHasher {
+			hmac_sha512: Hmac::new(Sha512::new(), &[0u8]),
+		}
+	}
+}
+
+impl BIP32Hasher for BIP32ReferenceHasher {
+	fn network_priv() -> [u8; 4] {
+		// bitcoin network (xprv) (for test vectors)
+		[0x04, 0x88, 0xAD, 0xE4]
+	}
+	fn network_pub() -> [u8; 4] {
+		// bitcoin network (xpub) (for test vectors)
+		[0x04, 0x88, 0xB2, 0x1E]
+	}
+	fn master_seed() -> [u8; 12] {
+		b"Bitcoin seed".to_owned()
+	}
+	fn init_sha512(&mut self, seed: &[u8]) {
+		self.hmac_sha512 = Hmac::new(Sha512::new(), seed);
+	}
+	fn append_sha512(&mut self, value: &[u8]) {
+		self.hmac_sha512.input(value);
+	}
+	fn result_sha512(&mut self) -> [u8; 64] {
+		let mut result = [0; 64];
+		self.hmac_sha512.raw_result(&mut result);
+		result
+	}
+	fn sha_256(&self, input: &[u8]) -> [u8; 32] {
+		let mut sha2_res = [0; 32];
+		let mut sha2 = Sha256::new();
+		sha2.input(input);
+		sha2.result(&mut sha2_res);
+		sha2_res
+	}
+	fn ripemd_160(&self, input: &[u8]) -> [u8; 20] {
+		let mut ripemd_res = [0; 20];
+		let mut ripemd = Ripemd160::new();
+		ripemd.input(input);
+		ripemd.result(&mut ripemd_res);
+		ripemd_res
+	}
+}
+
+/// Extended private key
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+pub struct ExtendedPrivKey {
+	/// The network this key is to be used on
+	pub network: [u8; 4],
+	/// How many derivations this key is from the master (which is 0)
+	pub depth: u8,
+	/// Fingerprint of the parent key (0 for master)
+	pub parent_fingerprint: Fingerprint,
+	/// Child number of the key used to derive from parent (0 for master)
+	pub child_number: ChildNumber,
+	/// Secret key
+	pub secret_key: SecretKey,
+	/// Chain code
+	pub chain_code: ChainCode,
+}
+
+/// Extended public key
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+pub struct ExtendedPubKey {
+	/// The network this key is to be used on
+	pub network: [u8; 4],
+	/// How many derivations this key is from the master (which is 0)
+	pub depth: u8,
+	/// Fingerprint of the parent key
+	pub parent_fingerprint: Fingerprint,
+	/// Child number of the key used to derive from parent (0 for master)
+	pub child_number: ChildNumber,
+	/// Public key
+	pub public_key: PublicKey,
+	/// Chain code
+	pub chain_code: ChainCode,
+}
+
+/// A child number for a derived key
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+pub enum ChildNumber {
+	/// Non-hardened key
+	Normal {
+		/// Key index, within [0, 2^31 - 1]
+		index: u32,
+	},
+	/// Hardened key
+	Hardened {
+		/// Key index, within [0, 2^31 - 1]
+		index: u32,
+	},
+}
+
+impl ChildNumber {
+	/// Create a [`Normal`] from an index, panics if the index is not within
+	/// [0, 2^31 - 1].
+	///
+	/// [`Normal`]: #variant.Normal
+	pub fn from_normal_idx(index: u32) -> Self {
+		assert_eq!(
+			index & (1 << 31),
+			0,
+			"ChildNumber indices have to be within [0, 2^31 - 1], is: {}",
+			index
+		);
+		ChildNumber::Normal { index: index }
+	}
+
+	/// Create a [`Hardened`] from an index, panics if the index is not within
+	/// [0, 2^31 - 1].
+	///
+	/// [`Hardened`]: #variant.Hardened
+	pub fn from_hardened_idx(index: u32) -> Self {
+		assert_eq!(
+			index & (1 << 31),
+			0,
+			"ChildNumber indices have to be within [0, 2^31 - 1], is: {}",
+			index
+		);
+		ChildNumber::Hardened { index: index }
+	}
+
+	/// Returns `true` if the child number is a [`Normal`] value.
+	///
+	/// [`Normal`]: #variant.Normal
+	pub fn is_normal(&self) -> bool {
+		!self.is_hardened()
+	}
+
+	/// Returns `true` if the child number is a [`Hardened`] value.
+	///
+	/// [`Hardened`]: #variant.Hardened
+	pub fn is_hardened(&self) -> bool {
+		match *self {
+			ChildNumber::Hardened { .. } => true,
+			ChildNumber::Normal { .. } => false,
+		}
+	}
+}
+
+impl From<u32> for ChildNumber {
+	fn from(number: u32) -> Self {
+		if number & (1 << 31) != 0 {
+			ChildNumber::Hardened {
+				index: number ^ (1 << 31),
+			}
+		} else {
+			ChildNumber::Normal { index: number }
+		}
+	}
+}
+
+impl From<ChildNumber> for u32 {
+	fn from(cnum: ChildNumber) -> Self {
+		match cnum {
+			ChildNumber::Normal { index } => index,
+			ChildNumber::Hardened { index } => index | (1 << 31),
+		}
+	}
+}
+
+impl fmt::Display for ChildNumber {
+	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+		match *self {
+			ChildNumber::Hardened { index } => write!(f, "{}'", index),
+			ChildNumber::Normal { index } => write!(f, "{}", index),
+		}
+	}
+}
+
+#[cfg(feature = "serde")]
+impl<'de> serde::Deserialize<'de> for ChildNumber {
+	fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+	where
+		D: serde::Deserializer<'de>,
+	{
+		u32::deserialize(deserializer).map(ChildNumber::from)
+	}
+}
+
+#[cfg(feature = "serde")]
+impl serde::Serialize for ChildNumber {
+	fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+	where
+		S: serde::Serializer,
+	{
+		u32::from(*self).serialize(serializer)
+	}
+}
+
+/// A BIP32 error
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub enum Error {
+	/// A pk->pk derivation was attempted on a hardened key
+	CannotDeriveFromHardenedKey,
+	/// A secp256k1 error occured
+	Ecdsa(secp::Error),
+	/// A child number was provided that was out of range
+	InvalidChildNumber(ChildNumber),
+	/// Error creating a master seed --- for application use
+	RngError(String),
+}
+
+impl fmt::Display for Error {
+	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+		match *self {
+			Error::CannotDeriveFromHardenedKey => {
+				f.write_str("cannot derive hardened key from public key")
+			}
+			Error::Ecdsa(ref e) => fmt::Display::fmt(e, f),
+			Error::InvalidChildNumber(ref n) => write!(f, "child number {} is invalid", n),
+			Error::RngError(ref s) => write!(f, "rng error {}", s),
+		}
+	}
+}
+
+impl error::Error for Error {
+	fn cause(&self) -> Option<&error::Error> {
+		if let Error::Ecdsa(ref e) = *self {
+			Some(e)
+		} else {
+			None
+		}
+	}
+
+	fn description(&self) -> &str {
+		match *self {
+			Error::CannotDeriveFromHardenedKey => "cannot derive hardened key from public key",
+			Error::Ecdsa(ref e) => error::Error::description(e),
+			Error::InvalidChildNumber(_) => "child number is invalid",
+			Error::RngError(_) => "rng error",
+		}
+	}
+}
+
+impl From<secp::Error> for Error {
+	fn from(e: secp::Error) -> Error {
+		Error::Ecdsa(e)
+	}
+}
+
+impl ExtendedPrivKey {
+	/// Construct a new master key from a seed value
+	pub fn new_master<H>(
+		secp: &Secp256k1,
+		hasher: &mut H,
+		seed: &[u8],
+	) -> Result<ExtendedPrivKey, Error>
+	where
+		H: BIP32Hasher,
+	{
+		hasher.init_sha512(&H::master_seed());
+		hasher.append_sha512(seed);
+		let result = hasher.result_sha512();
+
+		Ok(ExtendedPrivKey {
+			network: H::network_priv(),
+			depth: 0,
+			parent_fingerprint: Default::default(),
+			child_number: ChildNumber::from_normal_idx(0),
+			secret_key: SecretKey::from_slice(secp, &result[..32]).map_err(Error::Ecdsa)?,
+			chain_code: ChainCode::from(&result[32..]),
+		})
+	}
+
+	/// Attempts to derive an extended private key from a path.
+	pub fn derive_priv<H>(
+		&self,
+		secp: &Secp256k1,
+		hasher: &mut H,
+		cnums: &[ChildNumber],
+	) -> Result<ExtendedPrivKey, Error>
+	where
+		H: BIP32Hasher,
+	{
+		let mut sk: ExtendedPrivKey = *self;
+		for cnum in cnums {
+			sk = sk.ckd_priv(secp, hasher, *cnum)?;
+		}
+		Ok(sk)
+	}
+
+	/// Private->Private child key derivation
+	pub fn ckd_priv<H>(
+		&self,
+		secp: &Secp256k1,
+		hasher: &mut H,
+		i: ChildNumber,
+	) -> Result<ExtendedPrivKey, Error>
+	where
+		H: BIP32Hasher,
+	{
+		hasher.init_sha512(&self.chain_code[..]);
+		let mut be_n = [0; 4];
+		match i {
+			ChildNumber::Normal { .. } => {
+				// Non-hardened key: compute public data and use that
+				hasher.append_sha512(
+					&PublicKey::from_secret_key(secp, &self.secret_key)?.serialize_vec(secp, true)
+						[..],
+				);
+			}
+			ChildNumber::Hardened { .. } => {
+				// Hardened key: use only secret data to prevent public derivation
+				hasher.append_sha512(&[0u8]);
+				hasher.append_sha512(&self.secret_key[..]);
+			}
+		}
+		BigEndian::write_u32(&mut be_n, u32::from(i));
+
+		hasher.append_sha512(&be_n);
+		let result = hasher.result_sha512();
+		let mut sk = SecretKey::from_slice(secp, &result[..32]).map_err(Error::Ecdsa)?;
+		sk.add_assign(secp, &self.secret_key).map_err(Error::Ecdsa)?;
+
+		Ok(ExtendedPrivKey {
+			network: self.network,
+			depth: self.depth + 1,
+			parent_fingerprint: self.fingerprint(hasher),
+			child_number: i,
+			secret_key: sk,
+			chain_code: ChainCode::from(&result[32..]),
+		})
+	}
+
+	/// Returns the HASH160 of the chaincode
+	pub fn identifier<H>(&self, hasher: &mut H) -> [u8; 20]
+	where
+		H: BIP32Hasher,
+	{
+		let secp = Secp256k1::with_caps(ContextFlag::SignOnly);
+		// Compute extended public key
+		let pk: ExtendedPubKey = ExtendedPubKey::from_private::<H>(&secp, self);
+		// Do SHA256 of just the ECDSA pubkey
+		let sha2_res = hasher.sha_256(&pk.public_key.serialize_vec(&secp, true)[..]);
+		// do RIPEMD160
+		let ripemd_res = hasher.ripemd_160(&sha2_res);
+		// Return
+		ripemd_res
+	}
+
+	/// Returns the first four bytes of the identifier
+	pub fn fingerprint<H>(&self, hasher: &mut H) -> Fingerprint
+	where
+		H: BIP32Hasher,
+	{
+		Fingerprint::from(&self.identifier(hasher)[0..4])
+	}
+}
+
+impl ExtendedPubKey {
+	/// Derives a public key from a private key
+	pub fn from_private<H>(secp: &Secp256k1, sk: &ExtendedPrivKey) -> ExtendedPubKey
+	where
+		H: BIP32Hasher,
+	{
+		ExtendedPubKey {
+			network: H::network_pub(),
+			depth: sk.depth,
+			parent_fingerprint: sk.parent_fingerprint,
+			child_number: sk.child_number,
+			public_key: PublicKey::from_secret_key(secp, &sk.secret_key).unwrap(),
+			chain_code: sk.chain_code,
+		}
+	}
+
+	/// Attempts to derive an extended public key from a path.
+	pub fn derive_pub<H>(
+		&self,
+		secp: &Secp256k1,
+		hasher: &mut H,
+		cnums: &[ChildNumber],
+	) -> Result<ExtendedPubKey, Error>
+	where
+		H: BIP32Hasher,
+	{
+		let mut pk: ExtendedPubKey = *self;
+		for cnum in cnums {
+			pk = pk.ckd_pub(secp, hasher, *cnum)?
+		}
+		Ok(pk)
+	}
+
+	/// Compute the scalar tweak added to this key to get a child key
+	pub fn ckd_pub_tweak<H>(
+		&self,
+		secp: &Secp256k1,
+		hasher: &mut H,
+		i: ChildNumber,
+	) -> Result<(SecretKey, ChainCode), Error>
+	where
+		H: BIP32Hasher,
+	{
+		match i {
+			ChildNumber::Hardened { .. } => Err(Error::CannotDeriveFromHardenedKey),
+			ChildNumber::Normal { index: n } => {
+				hasher.init_sha512(&self.chain_code[..]);
+				hasher.append_sha512(&self.public_key.serialize_vec(secp, true)[..]);
+				let mut be_n = [0; 4];
+				BigEndian::write_u32(&mut be_n, n);
+				hasher.append_sha512(&be_n);
+
+				let mut result = hasher.result_sha512();
+
+				let secret_key = SecretKey::from_slice(secp, &result[..32])?;
+				let chain_code = ChainCode::from(&result[32..]);
+				Ok((secret_key, chain_code))
+			}
+		}
+	}
+
+	/// Public->Public child key derivation
+	pub fn ckd_pub<H>(
+		&self,
+		secp: &Secp256k1,
+		hasher: &mut H,
+		i: ChildNumber,
+	) -> Result<ExtendedPubKey, Error>
+	where
+		H: BIP32Hasher,
+	{
+		let (sk, chain_code) = self.ckd_pub_tweak(secp, hasher, i)?;
+		let mut pk = self.public_key.clone();
+		pk.add_exp_assign(secp, &sk).map_err(Error::Ecdsa)?;
+
+		Ok(ExtendedPubKey {
+			network: self.network,
+			depth: self.depth + 1,
+			parent_fingerprint: self.fingerprint(secp, hasher),
+			child_number: i,
+			public_key: pk,
+			chain_code: chain_code,
+		})
+	}
+
+	/// Returns the HASH160 of the chaincode
+	pub fn identifier<H>(&self, secp: &Secp256k1, hasher: &mut H) -> [u8; 20]
+	where
+		H: BIP32Hasher,
+	{
+		// Do SHA256 of just the ECDSA pubkey
+		let sha2_res = hasher.sha_256(&self.public_key.serialize_vec(secp, true)[..]);
+		// do RIPEMD160
+		let ripemd_res = hasher.ripemd_160(&sha2_res);
+		// Return
+		ripemd_res
+	}
+
+	/// Returns the first four bytes of the identifier
+	pub fn fingerprint<H>(&self, secp: &Secp256k1, hasher: &mut H) -> Fingerprint
+	where
+		H: BIP32Hasher,
+	{
+		Fingerprint::from(&self.identifier(secp, hasher)[0..4])
+	}
+}
+
+impl fmt::Display for ExtendedPrivKey {
+	fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+		let mut ret = [0; 78];
+		ret[0..4].copy_from_slice(&self.network[0..4]);
+		ret[4] = self.depth as u8;
+		ret[5..9].copy_from_slice(&self.parent_fingerprint[..]);
+
+		BigEndian::write_u32(&mut ret[9..13], u32::from(self.child_number));
+
+		ret[13..45].copy_from_slice(&self.chain_code[..]);
+		ret[45] = 0;
+		ret[46..78].copy_from_slice(&self.secret_key[..]);
+		fmt.write_str(&base58::check_encode_slice(&ret[..]))
+	}
+}
+
+impl FromStr for ExtendedPrivKey {
+	type Err = base58::Error;
+
+	fn from_str(inp: &str) -> Result<ExtendedPrivKey, base58::Error> {
+		let s = Secp256k1::without_caps();
+		let data = base58::from_check(inp)?;
+
+		if data.len() != 78 {
+			return Err(base58::Error::InvalidLength(data.len()));
+		}
+
+		let cn_int: u32 = Cursor::new(&data[9..13]).read_u32::<BigEndian>().unwrap();
+		let child_number: ChildNumber = ChildNumber::from(cn_int);
+
+		let mut network = [0; 4];
+		network.copy_from_slice(&data[0..4]);
+
+		Ok(ExtendedPrivKey {
+			network: network,
+			depth: data[4],
+			parent_fingerprint: Fingerprint::from(&data[5..9]),
+			child_number: child_number,
+			chain_code: ChainCode::from(&data[13..45]),
+			secret_key: SecretKey::from_slice(&s, &data[46..78])
+				.map_err(|e| base58::Error::Other(e.to_string()))?,
+		})
+	}
+}
+
+impl fmt::Display for ExtendedPubKey {
+	fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+		let secp = Secp256k1::without_caps();
+		let mut ret = [0; 78];
+		ret[0..4].copy_from_slice(&self.network[0..4]);
+		ret[4] = self.depth as u8;
+		ret[5..9].copy_from_slice(&self.parent_fingerprint[..]);
+
+		BigEndian::write_u32(&mut ret[9..13], u32::from(self.child_number));
+
+		ret[13..45].copy_from_slice(&self.chain_code[..]);
+		ret[45..78].copy_from_slice(&self.public_key.serialize_vec(&secp, true)[..]);
+		fmt.write_str(&base58::check_encode_slice(&ret[..]))
+	}
+}
+
+impl FromStr for ExtendedPubKey {
+	type Err = base58::Error;
+
+	fn from_str(inp: &str) -> Result<ExtendedPubKey, base58::Error> {
+		let s = Secp256k1::without_caps();
+		let data = base58::from_check(inp)?;
+
+		if data.len() != 78 {
+			return Err(base58::Error::InvalidLength(data.len()));
+		}
+
+		let cn_int: u32 = Cursor::new(&data[9..13]).read_u32::<BigEndian>().unwrap();
+		let child_number: ChildNumber = ChildNumber::from(cn_int);
+
+		let mut network = [0; 4];
+		network.copy_from_slice(&data[0..4]);
+
+		Ok(ExtendedPubKey {
+			network: network,
+			depth: data[4],
+			parent_fingerprint: Fingerprint::from(&data[5..9]),
+			child_number: child_number,
+			chain_code: ChainCode::from(&data[13..45]),
+			public_key: PublicKey::from_slice(&s, &data[45..78])
+				.map_err(|e| base58::Error::Other(e.to_string()))?,
+		})
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	extern crate crypto;
+
+	use std::str::FromStr;
+	use std::string::ToString;
+
+	use util::from_hex;
+	use util::secp::Secp256k1;
+
+	use super::ChildNumber::{Hardened, Normal};
+	use super::Error;
+	use super::{ChildNumber, ExtendedPrivKey, ExtendedPubKey};
+
+	use super::BIP32ReferenceHasher;
+
+	fn test_path(
+		secp: &Secp256k1,
+		seed: &[u8],
+		path: &[ChildNumber],
+		expected_sk: &str,
+		expected_pk: &str,
+	) {
+		let mut h = BIP32ReferenceHasher::new();
+		let mut sk = ExtendedPrivKey::new_master(secp, &mut h, seed).unwrap();
+		let mut pk = ExtendedPubKey::from_private::<BIP32ReferenceHasher>(secp, &sk);
+
+		// Check derivation convenience method for ExtendedPrivKey
+		assert_eq!(
+			&sk.derive_priv(secp, &mut h, path).unwrap().to_string()[..],
+			expected_sk
+		);
+
+		// Check derivation convenience method for ExtendedPubKey, should error
+		// appropriately if any ChildNumber is hardened
+		if path.iter().any(|cnum| cnum.is_hardened()) {
+			assert_eq!(
+				pk.derive_pub(secp, &mut h, path),
+				Err(Error::CannotDeriveFromHardenedKey)
+			);
+		} else {
+			assert_eq!(
+				&pk.derive_pub(secp, &mut h, path).unwrap().to_string()[..],
+				expected_pk
+			);
+		}
+
+		// Derive keys, checking hardened and non-hardened derivation one-by-one
+		for &num in path.iter() {
+			sk = sk.ckd_priv(secp, &mut h, num).unwrap();
+			match num {
+				Normal { .. } => {
+					let pk2 = pk.ckd_pub(secp, &mut h, num).unwrap();
+					pk = ExtendedPubKey::from_private::<BIP32ReferenceHasher>(secp, &sk);
+					assert_eq!(pk, pk2);
+				}
+				Hardened { .. } => {
+					assert_eq!(
+						pk.ckd_pub(secp, &mut h, num),
+						Err(Error::CannotDeriveFromHardenedKey)
+					);
+					pk = ExtendedPubKey::from_private::<BIP32ReferenceHasher>(secp, &sk);
+				}
+			}
+		}
+
+		// Check result against expected base58
+		assert_eq!(&sk.to_string()[..], expected_sk);
+		assert_eq!(&pk.to_string()[..], expected_pk);
+		// Check decoded base58 against result
+		let decoded_sk = ExtendedPrivKey::from_str(expected_sk);
+		let decoded_pk = ExtendedPubKey::from_str(expected_pk);
+		assert_eq!(Ok(sk), decoded_sk);
+		assert_eq!(Ok(pk), decoded_pk);
+	}
+
+	#[test]
+	fn test_vector_1() {
+		let secp = Secp256k1::new();
+		let seed = from_hex("000102030405060708090a0b0c0d0e0f".to_owned()).unwrap();
+
+		// m
+		test_path(&secp, &seed, &[],
+                  "xprv9s21ZrQH143K3QTDL4LXw2F7HEK3wJUD2nW2nRk4stbPy6cq3jPPqjiChkVvvNKmPGJxWUtg6LnF5kejMRNNU3TGtRBeJgk33yuGBxrMPHi",
+                  "xpub661MyMwAqRbcFtXgS5sYJABqqG9YLmC4Q1Rdap9gSE8NqtwybGhePY2gZ29ESFjqJoCu1Rupje8YtGqsefD265TMg7usUDFdp6W1EGMcet8");
+
+		// m/0h
+		test_path(&secp, &seed, &[ChildNumber::from_hardened_idx(0)],
+                  "xprv9uHRZZhk6KAJC1avXpDAp4MDc3sQKNxDiPvvkX8Br5ngLNv1TxvUxt4cV1rGL5hj6KCesnDYUhd7oWgT11eZG7XnxHrnYeSvkzY7d2bhkJ7",
+                  "xpub68Gmy5EdvgibQVfPdqkBBCHxA5htiqg55crXYuXoQRKfDBFA1WEjWgP6LHhwBZeNK1VTsfTFUHCdrfp1bgwQ9xv5ski8PX9rL2dZXvgGDnw");
+
+		// m/0h/1
+		test_path(&secp, &seed, &[ChildNumber::from_hardened_idx(0), ChildNumber::from_normal_idx(1)],
+                   "xprv9wTYmMFdV23N2TdNG573QoEsfRrWKQgWeibmLntzniatZvR9BmLnvSxqu53Kw1UmYPxLgboyZQaXwTCg8MSY3H2EU4pWcQDnRnrVA1xe8fs",
+                   "xpub6ASuArnXKPbfEwhqN6e3mwBcDTgzisQN1wXN9BJcM47sSikHjJf3UFHKkNAWbWMiGj7Wf5uMash7SyYq527Hqck2AxYysAA7xmALppuCkwQ");
+
+		// m/0h/1/2h
+		test_path(&secp, &seed, &[ChildNumber::from_hardened_idx(0), ChildNumber::from_normal_idx(1), ChildNumber::from_hardened_idx(2)],
+                  "xprv9z4pot5VBttmtdRTWfWQmoH1taj2axGVzFqSb8C9xaxKymcFzXBDptWmT7FwuEzG3ryjH4ktypQSAewRiNMjANTtpgP4mLTj34bhnZX7UiM",
+                  "xpub6D4BDPcP2GT577Vvch3R8wDkScZWzQzMMUm3PWbmWvVJrZwQY4VUNgqFJPMM3No2dFDFGTsxxpG5uJh7n7epu4trkrX7x7DogT5Uv6fcLW5");
+
+		// m/0h/1/2h/2
+		test_path(&secp, &seed, &[ChildNumber::from_hardened_idx(0), ChildNumber::from_normal_idx(1), ChildNumber::from_hardened_idx(2), ChildNumber::from_normal_idx(2)],
+                  "xprvA2JDeKCSNNZky6uBCviVfJSKyQ1mDYahRjijr5idH2WwLsEd4Hsb2Tyh8RfQMuPh7f7RtyzTtdrbdqqsunu5Mm3wDvUAKRHSC34sJ7in334",
+                  "xpub6FHa3pjLCk84BayeJxFW2SP4XRrFd1JYnxeLeU8EqN3vDfZmbqBqaGJAyiLjTAwm6ZLRQUMv1ZACTj37sR62cfN7fe5JnJ7dh8zL4fiyLHV");
+
+		// m/0h/1/2h/2/1000000000
+		test_path(&secp, &seed, &[ChildNumber::from_hardened_idx(0), ChildNumber::from_normal_idx(1), ChildNumber::from_hardened_idx(2), ChildNumber::from_normal_idx(2), ChildNumber::from_normal_idx(1000000000)],
+                  "xprvA41z7zogVVwxVSgdKUHDy1SKmdb533PjDz7J6N6mV6uS3ze1ai8FHa8kmHScGpWmj4WggLyQjgPie1rFSruoUihUZREPSL39UNdE3BBDu76",
+                  "xpub6H1LXWLaKsWFhvm6RVpEL9P4KfRZSW7abD2ttkWP3SSQvnyA8FSVqNTEcYFgJS2UaFcxupHiYkro49S8yGasTvXEYBVPamhGW6cFJodrTHy");
+	}
+
+	#[test]
+	fn test_vector_2() {
+		let secp = Secp256k1::new();
+		let seed = from_hex("fffcf9f6f3f0edeae7e4e1dedbd8d5d2cfccc9c6c3c0bdbab7b4b1aeaba8a5a29f9c999693908d8a8784817e7b7875726f6c696663605d5a5754514e4b484542".to_owned()).unwrap();
+
+		// m
+		test_path(&secp, &seed, &[],
+                  "xprv9s21ZrQH143K31xYSDQpPDxsXRTUcvj2iNHm5NUtrGiGG5e2DtALGdso3pGz6ssrdK4PFmM8NSpSBHNqPqm55Qn3LqFtT2emdEXVYsCzC2U",
+                  "xpub661MyMwAqRbcFW31YEwpkMuc5THy2PSt5bDMsktWQcFF8syAmRUapSCGu8ED9W6oDMSgv6Zz8idoc4a6mr8BDzTJY47LJhkJ8UB7WEGuduB");
+
+		// m/0
+		test_path(&secp, &seed, &[ChildNumber::from_normal_idx(0)],
+                  "xprv9vHkqa6EV4sPZHYqZznhT2NPtPCjKuDKGY38FBWLvgaDx45zo9WQRUT3dKYnjwih2yJD9mkrocEZXo1ex8G81dwSM1fwqWpWkeS3v86pgKt",
+                  "xpub69H7F5d8KSRgmmdJg2KhpAK8SR3DjMwAdkxj3ZuxV27CprR9LgpeyGmXUbC6wb7ERfvrnKZjXoUmmDznezpbZb7ap6r1D3tgFxHmwMkQTPH");
+
+		// m/0/2147483647h
+		test_path(&secp, &seed, &[ChildNumber::from_normal_idx(0), ChildNumber::from_hardened_idx(2147483647)],
+                  "xprv9wSp6B7kry3Vj9m1zSnLvN3xH8RdsPP1Mh7fAaR7aRLcQMKTR2vidYEeEg2mUCTAwCd6vnxVrcjfy2kRgVsFawNzmjuHc2YmYRmagcEPdU9",
+                  "xpub6ASAVgeehLbnwdqV6UKMHVzgqAG8Gr6riv3Fxxpj8ksbH9ebxaEyBLZ85ySDhKiLDBrQSARLq1uNRts8RuJiHjaDMBU4Zn9h8LZNnBC5y4a");
+
+		// m/0/2147483647h/1
+		test_path(&secp, &seed, &[ChildNumber::from_normal_idx(0), ChildNumber::from_hardened_idx(2147483647), ChildNumber::from_normal_idx(1)],
+                  "xprv9zFnWC6h2cLgpmSA46vutJzBcfJ8yaJGg8cX1e5StJh45BBciYTRXSd25UEPVuesF9yog62tGAQtHjXajPPdbRCHuWS6T8XA2ECKADdw4Ef",
+                  "xpub6DF8uhdarytz3FWdA8TvFSvvAh8dP3283MY7p2V4SeE2wyWmG5mg5EwVvmdMVCQcoNJxGoWaU9DCWh89LojfZ537wTfunKau47EL2dhHKon");
+
+		// m/0/2147483647h/1/2147483646h
+		test_path(&secp, &seed, &[ChildNumber::from_normal_idx(0), ChildNumber::from_hardened_idx(2147483647), ChildNumber::from_normal_idx(1), ChildNumber::from_hardened_idx(2147483646)],
+                  "xprvA1RpRA33e1JQ7ifknakTFpgNXPmW2YvmhqLQYMmrj4xJXXWYpDPS3xz7iAxn8L39njGVyuoseXzU6rcxFLJ8HFsTjSyQbLYnMpCqE2VbFWc",
+                  "xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL");
+
+		// m/0/2147483647h/1/2147483646h/2
+		test_path(&secp, &seed, &[ChildNumber::from_normal_idx(0), ChildNumber::from_hardened_idx(2147483647), ChildNumber::from_normal_idx(1), ChildNumber::from_hardened_idx(2147483646), ChildNumber::from_normal_idx(2)],
+                  "xprvA2nrNbFZABcdryreWet9Ea4LvTJcGsqrMzxHx98MMrotbir7yrKCEXw7nadnHM8Dq38EGfSh6dqA9QWTyefMLEcBYJUuekgW4BYPJcr9E7j",
+                  "xpub6FnCn6nSzZAw5Tw7cgR9bi15UV96gLZhjDstkXXxvCLsUXBGXPdSnLFbdpq8p9HmGsApME5hQTZ3emM2rnY5agb9rXpVGyy3bdW6EEgAtqt");
+	}
+
+	#[test]
+	fn test_vector_3() {
+		let secp = Secp256k1::new();
+		let seed = from_hex("4b381541583be4423346c643850da4b320e46a87ae3d2a4e6da11eba819cd4acba45d239319ac14f863b8d5ab5a0d0c64d2e8a1e7d1457df2e5a3c51c73235be".to_owned()).unwrap();
+
+		// m
+		test_path(&secp, &seed, &[],
+                  "xprv9s21ZrQH143K25QhxbucbDDuQ4naNntJRi4KUfWT7xo4EKsHt2QJDu7KXp1A3u7Bi1j8ph3EGsZ9Xvz9dGuVrtHHs7pXeTzjuxBrCmmhgC6",
+                  "xpub661MyMwAqRbcEZVB4dScxMAdx6d4nFc9nvyvH3v4gJL378CSRZiYmhRoP7mBy6gSPSCYk6SzXPTf3ND1cZAceL7SfJ1Z3GC8vBgp2epUt13");
+
+		// m/0h
+		test_path(&secp, &seed, &[ChildNumber::from_hardened_idx(0)],
+                  "xprv9uPDJpEQgRQfDcW7BkF7eTya6RPxXeJCqCJGHuCJ4GiRVLzkTXBAJMu2qaMWPrS7AANYqdq6vcBcBUdJCVVFceUvJFjaPdGZ2y9WACViL4L",
+                  "xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y");
+	}
+
+	#[test]
+	#[cfg(all(feature = "serde", feature = "strason"))]
+	pub fn encode_decode_childnumber() {
+		serde_round_trip!(ChildNumber::from_normal_idx(0));
+		serde_round_trip!(ChildNumber::from_normal_idx(1));
+		serde_round_trip!(ChildNumber::from_normal_idx((1 << 31) - 1));
+		serde_round_trip!(ChildNumber::from_hardened_idx(0));
+		serde_round_trip!(ChildNumber::from_hardened_idx(1));
+		serde_round_trip!(ChildNumber::from_hardened_idx((1 << 31) - 1));
+	}
+
+}
--- a/keychain/src/keychain.rs
+++ b/keychain/src/keychain.rs
@ -104,17 +104,21 @@ impl Keychain for ExtKeychain {
 			.filter_map(|k| self.derived_key(&k).ok())
 			.collect();

-		pos_keys.extend(&blind_sum
-			.positive_blinding_factors
-			.iter()
-			.filter_map(|b| b.secret_key(&self.secp).ok())
-			.collect::<Vec<SecretKey>>());
+		pos_keys.extend(
+			&blind_sum
+				.positive_blinding_factors
+				.iter()
+				.filter_map(|b| b.secret_key(&self.secp).ok())
+				.collect::<Vec<SecretKey>>(),
+		);

-		neg_keys.extend(&blind_sum
-			.negative_blinding_factors
-			.iter()
-			.filter_map(|b| b.secret_key(&self.secp).ok())
-			.collect::<Vec<SecretKey>>());
+		neg_keys.extend(
+			&blind_sum
+				.negative_blinding_factors
+				.iter()
+				.filter_map(|b| b.secret_key(&self.secp).ok())
+				.collect::<Vec<SecretKey>>(),
+		);

 		let sum = self.secp.blind_sum(pos_keys, neg_keys)?;
 		Ok(BlindingFactor::from_secret_key(sum))
@ -287,9 +291,11 @@ mod test {
 		// in the same way (convenience function)
 		assert_eq!(
 			keychain
-				.blind_sum(&BlindSum::new()
-					.add_blinding_factor(BlindingFactor::from_secret_key(skey1))
-					.add_blinding_factor(BlindingFactor::from_secret_key(skey2)))
+				.blind_sum(
+					&BlindSum::new()
+						.add_blinding_factor(BlindingFactor::from_secret_key(skey1))
+						.add_blinding_factor(BlindingFactor::from_secret_key(skey2))
+				)
 				.unwrap(),
 			BlindingFactor::from_secret_key(skey3),
 		);
--- a/keychain/src/lib.rs
+++ b/keychain/src/lib.rs
@ -16,6 +16,7 @@

 extern crate blake2_rfc as blake2;
 extern crate byteorder;
+#[macro_use]
 extern crate grin_util as util;
 extern crate rand;
 extern crate serde;
@ -24,9 +25,12 @@ extern crate serde_derive;
 extern crate serde_json;
 #[macro_use]
 extern crate slog;
+extern crate crypto;
 extern crate uuid;

+mod base58;
 pub mod extkey;
+pub mod extkey_bip32;
 mod types;

 pub mod keychain;
--- a/util/src/lib.rs
+++ b/util/src/lib.rs
@ -53,6 +53,8 @@ pub use secp_static::static_secp_instance;
 pub mod types;
 pub use types::{LogLevel, LoggingConfig};

+pub mod macros;
+
 // other utils
 use byteorder::{BigEndian, ByteOrder};
 use std::cell::{Ref, RefCell};
@ -62,10 +64,10 @@ use std::ops::Deref;
 mod hex;
 pub use hex::*;

-/// Compress and decompress zip bz2 archives
-pub mod zip;
 /// File util
 pub mod file;
+/// Compress and decompress zip bz2 archives
+pub mod zip;

 /// Encapsulation of a RefCell<Option<T>> for one-time initialization after
 /// construction. This implementation will purposefully fail hard if not used
--- a/util/src/macros.rs
+++ b/util/src/macros.rs
@ -0,0 +1,262 @@
+// Copyright 2018 The Grin Developers
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Rust Bitcoin Library
+// Written in 2014 by
+//     Andrew Poelstra <apoelstra@wpsoftware.net>
+//
+// To the extent possible under law, the author(s) have dedicated all
+// copyright and related and neighboring rights to this software to
+// the public domain worldwide. This software is distributed without
+// any warranty.
+//
+// You should have received a copy of the CC0 Public Domain Dedication
+// along with this software.
+// If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
+//
+
+//! Macros to support Rust BIP-32 code (though could conceivably be used for other things)
+
+#[macro_export]
+macro_rules! impl_array_newtype {
+    ($thing:ident, $ty:ty, $len:expr) => {
+        impl $thing {
+            #[inline]
+            /// Converts the object to a raw pointer
+            pub fn as_ptr(&self) -> *const $ty {
+                let &$thing(ref dat) = self;
+                dat.as_ptr()
+            }
+
+            #[inline]
+            /// Converts the object to a mutable raw pointer
+            pub fn as_mut_ptr(&mut self) -> *mut $ty {
+                let &mut $thing(ref mut dat) = self;
+                dat.as_mut_ptr()
+            }
+
+            #[inline]
+            /// Returns the length of the object as an array
+            pub fn len(&self) -> usize { $len }
+
+            #[inline]
+            /// Returns whether the object, as an array, is empty. Always false.
+            pub fn is_empty(&self) -> bool { false }
+
+            #[inline]
+            /// Returns the underlying bytes.
+            pub fn as_bytes(&self) -> &[$ty; $len] { &self.0 }
+
+            #[inline]
+            /// Returns the underlying bytes.
+            pub fn to_bytes(&self) -> [$ty; $len] { self.0.clone() }
+
+            #[inline]
+            /// Returns the underlying bytes.
+            pub fn into_bytes(self) -> [$ty; $len] { self.0 }
+        }
+
+        impl<'a> From<&'a [$ty]> for $thing {
+            fn from(data: &'a [$ty]) -> $thing {
+                assert_eq!(data.len(), $len);
+                let mut ret = [0; $len];
+                ret.copy_from_slice(&data[..]);
+                $thing(ret)
+            }
+        }
+
+        impl ::std::ops::Index<usize> for $thing {
+            type Output = $ty;
+
+            #[inline]
+            fn index(&self, index: usize) -> &$ty {
+                let &$thing(ref dat) = self;
+                &dat[index]
+            }
+        }
+
+        impl_index_newtype!($thing, $ty);
+
+        impl PartialEq for $thing {
+            #[inline]
+            fn eq(&self, other: &$thing) -> bool {
+                &self[..] == &other[..]
+            }
+        }
+
+        impl Eq for $thing {}
+
+        impl PartialOrd for $thing {
+            #[inline]
+            fn partial_cmp(&self, other: &$thing) -> Option<::std::cmp::Ordering> {
+                Some(self.cmp(&other))
+            }
+        }
+
+        impl Ord for $thing {
+            #[inline]
+            fn cmp(&self, other: &$thing) -> ::std::cmp::Ordering {
+                // manually implement comparison to get little-endian ordering
+                // (we need this for our numeric types; non-numeric ones shouldn't
+                // be ordered anyway except to put them in BTrees or whatever, and
+                // they don't care how we order as long as we're consisistent).
+                for i in 0..$len {
+                    if self[$len - 1 - i] < other[$len - 1 - i] { return ::std::cmp::Ordering::Less; }
+                    if self[$len - 1 - i] > other[$len - 1 - i] { return ::std::cmp::Ordering::Greater; }
+                }
+                ::std::cmp::Ordering::Equal
+            }
+        }
+
+        #[cfg_attr(feature = "clippy", allow(expl_impl_clone_on_copy))] // we don't define the `struct`, we have to explicitly impl
+        impl Clone for $thing {
+            #[inline]
+            fn clone(&self) -> $thing {
+                $thing::from(&self[..])
+            }
+        }
+
+        impl Copy for $thing {}
+
+        impl ::std::hash::Hash for $thing {
+            #[inline]
+            fn hash<H>(&self, state: &mut H)
+                where H: ::std::hash::Hasher
+            {
+                (&self[..]).hash(state);
+            }
+
+            fn hash_slice<H>(data: &[$thing], state: &mut H)
+                where H: ::std::hash::Hasher
+            {
+                for d in data.iter() {
+                    (&d[..]).hash(state);
+                }
+            }
+        }
+
+        impl ::rand::Rand for $thing {
+            #[inline]
+            fn rand<R: ::rand::Rng>(r: &mut R) -> $thing {
+                $thing(::rand::Rand::rand(r))
+            }
+        }
+    }
+}
+
+#[macro_export]
+macro_rules! impl_array_newtype_encodable {
+	($thing:ident, $ty:ty, $len:expr) => {
+		#[cfg(feature = "serde")]
+		impl<'de> $crate::serde::Deserialize<'de> for $thing {
+			fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+			where
+				D: $crate::serde::Deserializer<'de>,
+			{
+				use $crate::std::fmt::{self, Formatter};
+
+				struct Visitor;
+				impl<'de> $crate::serde::de::Visitor<'de> for Visitor {
+					type Value = $thing;
+
+					fn expecting(&self, formatter: &mut Formatter) -> fmt::Result {
+						formatter.write_str("a fixed size array")
+					}
+
+					#[inline]
+					fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
+					where
+						A: $crate::serde::de::SeqAccess<'de>,
+					{
+						let mut ret: [$ty; $len] = [0; $len];
+						for item in ret.iter_mut() {
+							*item = match seq.next_element()? {
+								Some(c) => c,
+								None => {
+									return Err($crate::serde::de::Error::custom("end of stream"))
+								}
+							};
+						}
+						Ok($thing(ret))
+					}
+				}
+
+				deserializer.deserialize_seq(Visitor)
+			}
+		}
+
+		#[cfg(feature = "serde")]
+		impl $crate::serde::Serialize for $thing {
+			fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+			where
+				S: $crate::serde::Serializer,
+			{
+				let &$thing(ref dat) = self;
+				(&dat[..]).serialize(serializer)
+			}
+		}
+	};
+}
+
+#[macro_export]
+macro_rules! impl_array_newtype_show {
+	($thing:ident) => {
+		impl ::std::fmt::Debug for $thing {
+			fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+				write!(f, concat!(stringify!($thing), "({:?})"), &self[..])
+			}
+		}
+	};
+}
+
+#[macro_export]
+macro_rules! impl_index_newtype {
+	($thing:ident, $ty:ty) => {
+		impl ::std::ops::Index<::std::ops::Range<usize>> for $thing {
+			type Output = [$ty];
+
+			#[inline]
+			fn index(&self, index: ::std::ops::Range<usize>) -> &[$ty] {
+				&self.0[index]
+			}
+		}
+
+		impl ::std::ops::Index<::std::ops::RangeTo<usize>> for $thing {
+			type Output = [$ty];
+
+			#[inline]
+			fn index(&self, index: ::std::ops::RangeTo<usize>) -> &[$ty] {
+				&self.0[index]
+			}
+		}
+
+		impl ::std::ops::Index<::std::ops::RangeFrom<usize>> for $thing {
+			type Output = [$ty];
+
+			#[inline]
+			fn index(&self, index: ::std::ops::RangeFrom<usize>) -> &[$ty] {
+				&self.0[index]
+			}
+		}
+
+		impl ::std::ops::Index<::std::ops::RangeFull> for $thing {
+			type Output = [$ty];
+
+			#[inline]
+			fn index(&self, _: ::std::ops::RangeFull) -> &[$ty] {
+				&self.0[..]
+			}
+		}
+	};
+}