keyfork

An opinionated and modular toolchain for generating and managing a wide range of cryptographic keys offline and on smartcards from a shared bip39 mnemonic phrase.

This toolchain uses a bip32 seed loaded into an agent to generate deterministic and unique keypairs. This ensures only the agent has control over the mnemonic itself, and other components can simply request deterministic data.

This repository must not be managed by cargo-hakari, to ensure each plumbing binary can be built with as few dependencies and SLOC to review as possible.

Dependency Policy

Dependencies must not be added to core utilities such as seed generation and path derivation without a really good reason we can't implement it ourselves, such as cryptography libraries. For instance, keyfork-derive-util only utilizes cryptography libraries, serde, and thiserror, with the latter two being audited dependencies. Utilities such as forklets (applications that use derived data, such as an OpenPGP keychain generator) and the kitchen-sink keyfork utility may pull in additional dependencies as needed, but should strive to use the standard library as much as possible. To avoid code reuse, additional crates (such as the smex crate) may be used to share functionality across several crates.

Keyfork Top-Level Binary

The keyfork binary is the most user-friendly interface for interacting with the Keyfork toolchain. It offers commands that should not take any scriptable input and should not produce any script-readable output. Such operations that require script compatibility should be made into their own utilities, with the higher level interface of interacting with them left solely to keyfork.

For instance, the program to generate system entropy is keyfork-entropy. It accepts an arbitrary length and spits out a hex-encoded chunk of data. The program to convert that entropy into a seed is keyfork-mnemonic-from-seed. It takes entropy from input and converts it into a seed. The combination of the two, generating entropy and converting it to a mnemonic, is managed through Keyfork: keyfork mnemonic generate, which can also be used to offer more options down the line, such as generating a mnemonic from tarot or playing cards, or dice.

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Note: The following document is all proposed, and not yet implemented.

Features

• Modular
  • Standalone binaries can derive/manage keys/config from bip32 root
  • Modules handle use cases like ssh, pgp, webauthn, crypto-assets, etc
  • Module contract is dead simple and can be written in any language
• Recoverable
  • Config file and 24 word mnemonic phrase to recover -all- keys
• Unpredictable
  • Generate a BIP39 phrase from OS entropy
  • Take BIP39 passphrase from user supplied entropy
  • Read up on https://milksad.info to understand why this matters!
• Offline
  • Will exit if network access is detected to force you to keep keys offline
  • Helps limit the risk of supply chain attacks
  • Intended for use with QubesOS Vault VM, AirgapOS, etc
  • Private keys are installed to HSMs/TEEs for use by online machines

Install

These steps will allow you to prove that at least two Distrust engineers signed off on the produced binaries, signaling that they reproduced them from source code and got identical results, in addition to our usual two-party code review processes.

This minimizes a single point of trust (and failure) in our binary release process.

See the Reproducible Builds project for more information on these practices.

We use git for all development, releases, and signing. Unfortunately git has no native method for large file storage or multi-signature workflows so some git add-ons are required.

To follow these steps please install git-lfs and git-sig.

1. Clone repo

   git clone https://git.distrust.co/public/keyfork
   cd keyfork
   

2. Review binary signatures

   git sig verify
   

   Note: See Trust section below for expected keys/signers

3. Install binary

   make install
   

Usage

keyfork generate [-c,--config=<file>]
    Generate new mnemonic optionally public keys defined by config
keyfork recover [-c,--config=<file>] [-a,--agent]
    Recover keychain and optionally config defined pubkeys from mnemonic
    Optionally run a daemon to supply keys to subcommands
keyfork version
	Show version information.
keyfork help
    Show this text.
keyfork [command]
    Commands receive bip32 root as stdin
    Commands return output and config data as json over stdout back to keyfork
keyfork [command] help
    Show help for a particular sub-command

Examples

Generate a new mnemonic to write to paper

$ keyfork generate

> milk sad wage cup reward umbrella raven visa give list decorate bulb gold raise twenty fly manual stand float super gentle climb fold park

Recover a mnemonic with a passphrase and spawn agent

$ keyfork recover --agent

> mnemonic: ********
> passphrase: ********

Derive deterministic PGP keychain from agent key in default "sq" path

Requires keyfork-pgp binary in $PATH

$ keyfork pgp --format=sq
$ sq decrypt secret.pgp

Install deterministic PGP subkeys from agent key to a smartcard

Requires keyfork-pgp binary in $PATH

$ keyfork pgp install --device=nitrokey
$ gpg --card-status

Install first deterministic PIV key from agent key to smartcard on slot 1

Requires keyfork-piv binary in $PATH

$ keyfork piv install --device=yubikey --key=1 --slot=1

> Management Key: ****
> User Pin: ****
> Admin Pin: ****

$ ssh-keygen -D "$OPENSC_LIBS/opensc-pkcs11.so" -e

Derive first deterministic BIP44 address for Bitcoin Account 1

Requires keyfork-bip44 binary in $PATH

$ keyfork bip44 --path=bitcoin

> m/44'/0'/0'/0/0: 12DefCMhYVv4sBQikyXKMciAoX2wgzhWqb