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Blockchain Commons LetheKit

Open source DIY hardware box for offline cryptographic tools

by Ken Sedgwick, Gorazd Kovacic, and Christopher Allen


LetheKit is a do-it-youself platform for performing various sensitive cryptographic operations on an offline airgapped device. It uses no WiFi or Bluetooth which could leak information and contains no local storage, and when the device is turned off it forgets any sensitive data stored in RAM. Thus the name Lethe (lee-thee), from the mythological river of forgetfulness and oblivion.

Additional Information

The following files contain everything you need to set up your LetheKit hardware and install its software.

Your LetheKit can be charged or recharged with a micro-USB connection.

Gordian Principles

Gordian LetheKit is a hardware exemplar meant to display the Gordian Principles, which are philosophical and technical underpinnings to Blockchain Commons' Gordian technology. This includes:

  • Independence. LetheKit ensures that you're in total control of your seeds.
  • Privacy. LetheKit is totally offline.
  • Resilience. LetheKit depends on you for its resilience, since you must back up your words or codes.
  • Openness. LetheKit communicates through airgaps via URs and QRs, for maximum interoperability.

Blockchain Commons apps do not phone home and do not run ads. Some are available through various app stores; all are available in our code repositories for your usage.

Status - Late Alpha

LetheKit is currently under active development and in the late alpha testing phase. It should not be used for production tasks until it has had further testing and auditing.

⚠️ Warning: Lack of Round-trip Compatibility between BIP-39 and SLIP-39

At first glance, BIP-39 and SLIP-39 both appear to be means of converting a binary seed to a set of backup words and back. You might assume you could simply convert a BIP-39 backup to a binary seed, from that binary seed to SLIP-39, and then use the SLIP-39 backup to recover the same wallet as the original BIP-39 backup, but this is NOT the case. This is because the SLIP-39 algorithm that SatoshiLabs uses in their Trezor wallet does not derive the master secret in the same way as their BIP-39 algorithm does.

Currently Blockchain Commons and LetheKit implement an alternative to SLIP-39, called Sharded Secret Key Reconstruction (SSKR), that allows round-trips with BIP-39. We want to ensure that the same seed will result in the same derived keys using either BIP-39 or our alternative approach.

As SLIP-39 is not round-trip compatible with BIP-39, and SLIP-39 is under the control of SatoshiLabs and does not appear to be a fully community-controlled standard, Blockchain Commons is no longer endorsing SLIP-39.

  • This issue is being tracked here.

Unless otherwise noted (either in this / or in the file's header comments) the contents of this repository are Copyright © 2020 by Blockchain Commons, LLC, and are licensed under the spdx:BSD-2-Clause Plus Patent License.

In most cases, the authors, copyright, and license for each file reside in header comments in the source code. The table below attempts to attribute accurately for files without such information.

This table below also establishes provenance (repository of origin, permalink, and commit id) for files included from repositories that are outside of this one. Contributors to these files are listed in the commit history for each repository, first with changes found in the commit history of this repo, then in changes in the commit history of their repo of their origin.

File From Commit Authors & Copyright (c) License
Cryptosuite ae0e3eeb4eb00c53fe235e0c34f77ade11f1982a 2010 Peter Knight
bip39 9b8fa3c7d145c39558c2534f6cf40879477d93a1 2018 Chris Howe MIT License
TRNG-for-ATSAMD51J19A-Adafruit-Metro-M4- 17d5e36cd922ce7df8047d9c89633dca9b5ae122 2019 Ron Sutton MIT License
libwally-core e0d0634aea716d813744326ea6c7590eb9fc381c Jon Griffiths (Blockstream) 2016 BSD/MIT license
Library-arduino-cbor 996bf4a853513ee1fb94286691209a067c915bfb jjtara 2014 Apache license
ArduinoSTL 7411816e2d8f49d96559dbaa47e327816dde860c Mike Matera 1999 GNU LGPL


To build the LetheKit you'll need to use the following exterinal tools:

The following internal Blockchain Commons projects are leveraged by LetheKit:

Derived from ...

The LetheKit project was inspired by:

Used with ...

These are other projects that work with or leverage LetheKit.

  • (submit a PR to this repo list your project)

Financial Support

LetheKit (lee-thee kit) is a project of Blockchain Commons. We are proudly a "not-for-profit" social benefit corporation committed to open source & open development. Our work is funded entirely by donations and collaborative partnerships with people like you. Every contribution will be spent on building open tools, technologies, and techniques that sustain and advance blockchain and internet security infrastructure and promote an open web.

To financially support further development of LetheKit and other projects, please consider becoming a Patron of Blockchain Commons through ongoing monthly patronage as a GitHub Sponsor. You can also support Blockchain Commons with bitcoins at our BTCPay Server.

Project Sponsors

Thanks to our project sponsors for their support of LetheKit:

Keystone is the manufacturer of the Keystone Hardware Wallet and the Keystone Tablets. Their focus is on uncompromising security and ease of use, taking human error into consideration, skyrocketing attack costs, reducing burdens of proof, and avoiding single points of failure.


We encourage public contributions to this project through issues and pull requests! Please review for details on our development process. All contributions to this repository require a GPG signed Contributor License Agreement.


The best place to talk about Blockchain Commons and its projects is in our GitHub Discussions areas.

Gordian User Community. For users of the Gordian reference apps, including Gordian Coordinator, Gordian Seed Tool, Gordian Server, Gordian Wallet, and SpotBit as well as our whole series of CLI apps. This is a place to talk about bug reports and feature requests as well as to explore how our reference apps embody the Gordian Principles.

Blockchain Commons Discussions. For developers, interns, and patrons of Blockchain Commons, please use the discussions area of the Community repo to talk about general Blockchain Commons issues, the intern program, or topics other than those covered by the Gordian Developer Community or the Gordian User Community.

Other Questions & Problems

As an open-source, open-development community, Blockchain Commons does not have the resources to provide direct support of our projects. Please consider the discussions area as a locale where you might get answers to questions. Alternatively, please use this repository's issues feature. Unfortunately, we can not make any promises on response time.

If your company requires support to use our projects, please feel free to contact us directly about options. We may be able to offer you a contract for support from one of our contributors, or we might be able to point you to another entity who can offer the contractual support that you need.


The following people directly contributed to this repository. You can add your name here by getting involved; the first step is to learn how to contribute from our documentation.

Name Role Github Email GPG Fingerprint
Christopher Allen Principal Architect @ChristopherA <> FDFE 14A5 4ECB 30FC 5D22 74EF F8D3 6C91 3574 05ED
Ken Sedgwick Original Author, Occasional Contributor @ksedgwic <> 4695 E5B8 F781 BF85 4326 9639 BBFC E515 8602 5550
Gorazd Kovacic developer @gorazdko <> 41F0 EA16 99A7 4C1E 2FA4 1B53 8CF9 6BC3 FF9D BBCE

Responsible Disclosure

We want to keep all our software safe for everyone. If you have discovered a security vulnerability, we appreciate your help in disclosing it to us in a responsible manner. We are unfortunately not able to offer bug bounties at this time.

We do ask that you offer us good faith and use best efforts not to leak information or harm any user, their data, or our developer community. Please give us a reasonable amount of time to fix the issue before you publish it. Do not defraud our users or us in the process of discovery. We promise not to bring legal action against researchers who point out a problem provided they do their best to follow the these guidelines.

Reporting a Vulnerability

Please report suspected security vulnerabilities in private via email to (do not use this email for support). Please do NOT create publicly viewable issues for suspected security vulnerabilities.

The following keys may be used to communicate sensitive information to developers:

Name Fingerprint
Christopher Allen FDFE 14A5 4ECB 30FC 5D22 74EF F8D3 6C91 3574 05ED

You can import a key by running the following command with that individual’s fingerprint: gpg --recv-keys "<fingerprint>" Ensure that you put quotes around fingerprints that contain spaces.