[Top]

Delegated appraisal

In some sense, the delegated appraisal use case represents the mirror-image of the certificate-style use case. In the certificate-style structure, the attester is responsible for submitting evidence to the appraiser and obtaining the appraiser’s endorsement of the acceptability of that evidence. Here, the attester simply prepares the requested evidence and hands it off to the relying party. It is the responsibility of the relying party to seek the appraiser’s endorsement.

The scenario we envision for this use case is identical to that of the certificate-style use case. A client wishes to log into their bank’s website but will not furnish a proof of identity (i.e. provide account credentials) until it has obtained some assurance that the bank website is uncompromised. The client may moreover be unable to appraise the bank’s evidence, and so the bank and client agree to rely on the endorsement of a mutually trusted third-party appraiser to complete the attestation. The client submits the bank’s evidence to the appraiser for appraisal, and the appraiser responds with the results of appraisal in a format the client understands. The client can then use the appraisal results to make a trust decision about the compromise state of the bank’s system.

  ┌────────────────┐
  │                │
  │   appraiser    │
  │                │ 
  │                │
  └────────────────┘
       │      ▲
       │      │
       │      │
result │      │ attest
       │      │
       │      │
       ▼      │
  ┌────────────────┐              ┌────────────────┐              
  │                │      req     │                │
  │     client     │─────────────►│      bank      │
  │                │     attest   │                │
  │                │◄─────────────│                │
  └────────────────┘              └────────────────┘

Each example contains a Copland phrase describing this attestation structure. The first two examples consider the case in which only the bank attests. The latter two elaborate on this and consider the case in which both client and bank furnish attestations, both mediated by the appraiser. We recommend visiting these examples in order, and we strongly recommend new Copland users begin with the mutual attestation use case before proceeding to these examples.