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Catalyst HD Key Derivation for Off Chain Keys

Abstract

Project Catalyst uses off chain keys, as a proxy for on-chain keys. These keys need to be derived similar to the keys controlled by a wallet. This document defines the Derivation path.

Motivation: why is this CIP necessary?

A user will need a number of self generated and controlled signature and other keys. They will need to be able to recover them from a known seed phrase, and also to roll them over.

This allows users to replace keys, and have them fully recoverable. Which they may have to do if:

  • Their keys are lost, and the account has to be recovered, or moved to a different device.
  • Their keys are compromised (or suspected to be compromised), and they have to be replaced.

The keys are not controlled by a Blockchain wallet. They are agnostic of any blockchain. So, Project Catalyst must implement similar mechanisms as the wallets to safely derive keys for its use.

Specification

For reference, see [CIP-1852]. This document is a modified implementation of this specification.

The basic structure of the Key Derivation path shall be:

m / purpose' / type' / usage' / role / index

purpose'

Defines the purpose of the key, a distinct value from the one chosen for cardano is used to prevent collision with keys derived by wallets if the same seed phrase were to be used. Cardano uses a notable year that aligns with Cardano ecosystem philosophy, we maintain that practice but choose alternative historical dates.

  • Value: 508
  • Name in [CIP-1852]: purpose'
  • Hardened: YES
  • Represents: Taken from year 508 BCE, the first known instance of democracy in human history. "The Athenian Revolution, a revolt that overthrew the aristocratic oligarchy and established a participatory democracy in Athens".

type'

Defines the type of the key, a distinct value from the one chosen for cardano is used to prevent collision with keys derived by wallets if the same seed phrase were to be used. Cardano uses a notable year that aligns with Cardano ecosystem philosophy, we maintain that practice but choose alternative historical dates.

  • Value: 139
  • Name in [CIP-1852]: coin_type'
  • Hardened: YES
  • Represents: Taken from the year 139 BCE, the first known instance of secret voting. "A secret ballot is instituted for Roman citizens, who mark their vote on a tablet and place it in an urn."

usage'

Defines how the derived key will be used. This occupies the same position as account' in [CIP-1852].

  • Value: positive integer (0-n)
  • Name in [CIP-1852]: account'
  • Hardened: YES

| usage' | Name | | 0 | ED25519 Document Signing Key | | 1 | Used to derive a Root Symmetric encryption key used for encrypting data within a document. | | 2+ | Currently undefined. |

role

The role in the derivation maps 1:1 with the role number in the RBAC registration the key will be used for.

  • Value: positive integer (0-n)
  • Name in [CIP-1852]: role
  • Hardened: NO

index

The sequentially derived key in a sequence, starting at 0. Each new key for the same role just increments index. This is mapped 1:1 to the rotation field in a Catalyst ID.

  • Value: positive integer (0-n)
  • Name in [CIP-1852]: index
  • Hardened: NO

Reference Implementation

The first implementation will be for ED25519 Document Signing Key in Catalyst Voices.

TODO: Generate a set of test vectors which conform to this specification.

Rationale: how does this CIP achieve its goals?

By leveraging known working Key Derivation techniques and simply modifying the path we inherit the properties of those methods.

Path to Active

Acceptance Criteria

Working Implementation before Fund 14.

Implementation Plan

Fund 14 project catalyst will deploy this scheme for Key derivation.>

This document is licensed under CC-BY-4.0