HD Path for Rust

Rust crate that implements common structures and utilities to operate HD Path defined by Bitcoin’s BIP-32 standard.

The main specification for the Hierarchical Deterministic Wallets is BIP-32, and HD Path is a part of it which specifies the format for the hierarchy path.

The crate doesn’t try to implement Key Derivation specification, but instead implements all common functionality for creating, parsing and displaying an HD Path, especially standard paths defined by BIP-44 and related.

The common structure, defined by BIP-43, is m/purpose'/coin_type'/account'/change/address_index, for example m/44'/0'/0'/0/0

All supported standards:

• BIP-32

• BIP-43

• BIP-44

• BIP-49

• BIP-84

Use

Cargo.toml:

[dependencies]
hdpath = "0.5.0"

Examples

Basic usage

use hdpath::StandardHDPath;
use std::str::FromStr;

let hd_path = StandardHDPath::from_str("m/44'/0'/0'/0/0").unwrap();
//prints "m/44'/0'/0'/0/0"
println!("{:?}", hd_path);

//prints "0", which is account id
println!("{:?}", hd_path.account());

//prints: "purpose: Pubkey, coin: 0, account: 0, change: 0, index: 0"
println!("purpose: {:?}, coin: {}, account: {}, change: {}, index: {}",
    hd_path.purpose(),
    hd_path.coin_type(),
    hd_path.account(),
    hd_path.change(),
    hd_path.index()
);

Create from values

use hdpath::{StandardHDPath, Purpose};

let hd_path = StandardHDPath::new(Purpose::Witness, 0, 1, 0, 101);
//prints "m/84'/0'/1'/0/101"
println!("{:?}", hd_path);

Create account and derive addresses

use hdpath::{AccountHDPath, StandardHDPath, Purpose};
use std::convert::TryFrom;

let hd_account = AccountHDPath::new(Purpose::Witness, 0, 1);
// prints "m/44'/0'/1'/x/x"
println!("{:?}", hd_account);

// get actual address on the account path. Returns StandardHDPath
let hd_path = hd_account.address_at(0, 7);

//prints: "m/44'/0'/1'/0/7"
println!("{:?}", hd_path);

Please note that values for HD Path are limited to 2^31-1 because the highest bit is reserved for marking a hardened value. Therefore, if you’re getting individual values from some user input, you should verify the value before passing to ::new. Otherwise, the constructor may fail with panic if an invalid value is passed.

Verify before create

use hdpath::{StandardHDPath, PathValue, Purpose};

fn user_path(index: u32) -> Result<StandardHDPath, ()> {
  let user_id = 1234 as u32;
  if PathValue::is_ok(index) {
    Ok(StandardHDPath::new(Purpose::Witness, 0, user_id, 0, index))
  } else {
    Err(())
  }
}

Use with bitcoin library

Enable with-bitcoin feature, that provides extra methods for compatibility with bitcoin lib. It includes conversion into Vec<ChildNumber> and DerivationPath.

hdpath = { version = "0.5.0", features = ["with-bitcoin"] }

Convert to DerivationPath

use hdpath::{StandardHDPath};
use secp256k1::Secp256k1;
use bitcoin::{
    network::constants::Network,
    util::bip32::{ExtendedPrivKey, DerivationPath}
};

fn get_pk(seed: &[u8], hd_path: &StandardHDPath) -> ExtendedPrivKey {
  let secp = Secp256k1::new();
  ExtendedPrivKey::new_master(Network::Bitcoin, seed)
        // we convert HD Path to bitcoin lib format (DerivationPath)
        .and_then(|k| k.derive_priv(&secp, &DerivationPath::from(hd_path)))
        .unwrap()
}

License

Copyright 2020 EmeraldPay, Inc

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.