Crate hkd32

Expand description

HMAC-based Hierarchical Key Derivation: deterministically derive a hierarchy of symmetric keys from initial keying material through repeated applications of the Hash-based Message Authentication Code (HMAC) construction.

This library implements a fully symmetric construction inspired by BIP-0032: Hierarchical Deterministic Wallets.

Usage

To derive a key using HKD32, you’ll need the following:

KeyMaterial: a 32-byte (256-bit) uniformly random value
Path or PathBuf: path to the child key

Derivation paths can be raw bytestrings but also support a Unix path-like syntax which can be parsed using the String::parse method:

let path = "/foo/bar/baz".parse::<hkd32::PathBuf>().unwrap();

Example

use rand_core::OsRng;

// Parent key
let input_key_material = hkd32::KeyMaterial::random(&mut OsRng);

// Path to the child key
let derivation_path = "/foo/bar/baz".parse::<hkd32::PathBuf>().unwrap();

// Derive subkey from the parent key. Call `as_bytes()` on this to obtain
// a byte slice containing the derived key.
let output_key_material = input_key_material.derive_subkey(derivation_path);