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Mutual attestation

In this use case, we envision a scenario in which two parties produce evidence resulting from a local measurement. Each party wishes to communicate its result to the other for appraisal, but one of the parties will not do so until it has appraised the other’s evidence and found it acceptable. The mutual attestation thus consists of two unilateral attestations that occur in a particular order.

We use the example of a client who wishes to log into their bank’s website. Before granting access, the bank requires the client to authenticate with their username and password, i.e. present a proof of identity. However, the client does not wish to share their credentials with the bank website until they are assured that the bank’s systems are uncompromised. The bank must first present its proof of system integrity for the client to appraise, and the results of appraisal must indicate the bank’s systems are pristine, before the client will reply with its proof of identity to complete the login request.

Each example below contains a Copland phrase written to address this scenario. Later examples are generally refinements of earlier ones. It is recommended, especially for readers who are new to Copland, to begin with the first example and proceed in order.