Aries RFC 0051: Decentralized Key Management

• Authors: Drummond Reed et al.
• Status: RETIRED
• Since: 2024-04-03
• Status Note: Covered elsewhere and not specific to Aries.
• Start Date: 2018-09-01 (approx, backdated)
• Tags: concept

Summary

Describes a general approach to key management in a decentralized, self-sovereign world. We expect Aries to embody the principles described here; this doc is likely to color numerous protocols and ecosystem ../../features.

Motivation

A decentralized key management system (DKMS) is an approach to cryptographic key management where there is no central authority. DKMS leverages the security, immutability, availability, and resiliency properties of distributed ledgers to provide highly scalable key distribution, verification, and recovery.

Key management is vital to exercising sovereignty in a digital ecosystem, and decentralization is a vital principle as well. Therefore, we need a coherent and comprehensive statement of philosophy and architecture on this vital nexus of topics.

Tutorial

The bulk of the content for this RFC is located in the official architecture documentation -- dkms-v4.md; readers are encouraged to go there to learn more. Here we present only the highest-level background context, for those who may be unaware of some basics.

Background Concepts

Key Types

DKMS uses the following key types: 1. Master keys: Keys that are not cryptographically protected. They are distributed manually or initially installed and protected by procedural controls and physical or electronic isolation. 2. Key encrypting keys: Symmetric or public keys used for key transport or storage of other keys. 3. Data keys: Used to provide cryptographic operations on user data (e.g., encryption, authentication).

The keys at one level are used to protect items at a lower level. Consequently, special measures are used to protect master keys, including severely limiting access and use, hardware protection, and providing access to the key only under shared control.

Key Loss

Key loss means the owner no longer controls the key and it can assume there is no further risk of compromise. For example devices unable to function due to water, electricity, breaking, fire, hardware failure, acts of God, etc.

Compromise

Key compromise means that private keys and/or master keys have become or can become known either passively or actively.

Recovery

In decentralized identity management, recovery is important since identity owners have no “higher authority” to turn to for recovery. 1. Offline recovery uses physical media or removable digital media to store recovery keys. 2. Social recovery employs entities trusted by the identity owner called "trustees" who store recovery data on an identity owners behalf—typically in the trustees own agent(s).

These methods are not exclusive and should be combined with key rotation and revocation for proper security.

Reference

1. Design and architecture
2. Public Registry for Agent Authorization Policy. An identity owner creates a policy on the ledger that defines its agents and their authorizations. Agents while acting on the behalf of the identity owner need to prove that they are authorised. More details
3. Shamir Secret
4. Trustee Protocols

Drawbacks, Rationale and alternatives, Prior art, Unresolved Questions

The material that's normally in these sections of a RFC appears in the official architecture documentation -- dkms-v4.md.

Implementations

The following lists the implementations (if any) of this RFC. Please do a pull request to add your implementation. If the implementation is open source, include a link to the repo or to the implementation within the repo. Please be consistent in the "Name" field so that a mechanical processing of the RFCs can generate a list of all RFCs supported by an Aries implementation.

Name / Link	Implementation Notes
Indy SDK	partial: backup
Connect.Me	partial: backup, sync to cloud