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Blockchain Commons SmartCustody

by Christopher Allen and Shannon Appelcline

SmartCustody is an educational project intended to encourage responsible key management for digital assets. It includes a book focused on risk modeling and digital custody scenarios as well as a number of shorter papers that focus on individual "smart" methodologies for managing digital custody, such as multisigs and sharded shares.

The SmartCustody Book

SmartCustody Scenarios

We've recently supplemented the Cold-Storage scenario found in #SC 1.01 with a new multisig scenario:

  • Multisig Self-Custody Scenario (April 2022) — Draft of a specific scenario for multisig, currently seeking feedback on the overall thinking. Will be expanded in the future to support more signing devices and even transaction coordinators.

SmartCustody Tools

The following long-form essays describe how to use a variety of smart tools to improve the resilience and security of your digital assets.


SSKR Shares:


SmartCustody Case Studies

Analyses of how professional apps and hardware devices accomodate Gordian Principles and defeat SmartCustody adversaries.

SmartCustody Best Practices

The following smaller topics are simple suggesting for maintaing robust security.

Gordian Apps

All of the Gordian apps are SmartCustody apps, because they highlight the Gordian Principles, including resilience. They also tend to use SmartCustody tools such as multisigs and SSKR. However, some are of particular note, because they're also built to solve very specific SmartCustody problems.

  • mori-cli — A miniscript-based app that uses timelocks to ensure the continuity of funds following death or incapacitation.

Gordian Principles

SmartCustody displays how to use the Gordian Principles, which are philosophical and technical underpinnings to Blockchain Commons' Gordian technology, to ensure responsible key management.

  • Independence. SmartCustody suggests self-sovereign scenarios, where you control your keys.
  • Privacy. A minor element of SmartCustody, privacy should innately develop from the independent scenarios.
  • Resilience. SmartCustody combats two major problems: it makes sure keys aren't lost or stolen.
  • Openness. The procedures of SmartCustody use standard, non-proprietary methods, such as multisigs, timelocks, and Shamir's Secret Sharing.

Status - Ongoing

SmartCustody is an ongoing process. See the individual descriptions of books and articles.

Origin, Authors, Copyright & Licenses

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. When it does not, we have attempted to attribute it accurately in the table below.

Financial Support

SmartCustody 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 $projectname 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.


We encourage public contributions 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 Developer Community. For standards and open-source developers who want to talk about interoperable wallet specifications, please use the Discussions area of the Gordian Developer Community repo. This is where you talk about Gordian specifications such as Gordian Envelope, bc-shamir, Sharded Secret Key Reconstruction, and bc-ur as well as the larger Gordian Architecture, its Principles of independence, privacy, resilience, and openness, and its macro-architectural ideas such as functional partition (including airgapping, the original name of this community).

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 learning 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
Shannon Appelcline Co-Author @shannona <> 7EC6 B928 606F 27AD

Responsible Disclosure

We want to keep all of 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.