steel_thread

README

Steel Thread Signing & Verification

Overview

Annotated steel thread flow for calling out all signing, verification, and key management. This document is focused on the signing and verification of objects. For Steel Thread, this means: Credentials and Credential Manifest request objects.

Setup

We assume there are two parties:

1. Alice, using a wallet, applying for a credential
2. An issuer via the SSI Service, processing credential applications and issuing credentials

Each party has a single DID. Alice and the SSI Service each have a single [did:key](https://w3c-ccg.github.io/did-method-key/) DID. Alice stores her DID’s private key in her wallet. The SSI Service stores its private key in the service key store database.

Actors

For simplicity the DWN is abstracted from the description and diagrams below, since it plays no role in issuing or verifying credentials or credential manifest objects.

Alice and the Issuer are also abstracted from the diagram. Instead focusing on the software handling signing and verification — Alice’s Wallet and the SSI Service.

Flow Annotation

🛠 All objects are signed using `did:key` DIDs using `Ed25519` keys. Packaging takes place using JWTs.

1. Alice creates a DID, stored in her wallet, didW
2. The issuer creates a DID, stored in the SSI Service, didI
3. [CM is a JWT] The Credential Manifest CM is created and signed by the Issuer, with didI
4. Alice fetches CM and…
   1. Validates the signature using didI
   2. Verifies it is a valid and well-formed Credential Manifest
5. [CA is a JWT] Alice forms a response to CM, Credential Application CA
   1. Alice signs CA using didW
6. Alice submits CA to the SSI Service
7. The SSI Service processes CA...
   1. Validates the signature using didW
   2. Verifies it is a valid and well-formed Credential Application
   3. Validates it complies with CM
8. [VC is a VC-JWT] The SSI Service creates Verifiable Credentials, VC, signed with didI
9. [CR is a JWT] The SSI Service creates a Credential Response, CR, signed with didI
10. Alice receives CR containing VC and…
    1. Validates the signature of the CR using didI
    2. Verifies CR and VC are well-formed
    3. Verifies the signature(s) of VC using didI
    4. Possible other validity checks, such as making sure the Credential is for Alice and has expected data
11. Alice stores the VC