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keyserver-usecase.md

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Example of a complete Keyserver use-case

Parties:

  • Keyserver
  • Alice (recipient)
  • Bob (sender, session initiation)

Key Hashchain initialization: Bob & Alice

  • Call KeyRepository.Capabilities() to learn keyserver capabilities.
  • Repeatedly call KeyRepository.FetchHashChain() to download the Hashchain in chunks, starting with position 0 and ending with last entry.
  • Track Keyserver identity through the hashchain to always have valid signature keys.

Becoming a user: Alice

Alice generates SIGKEY and SIGESCROW keys. The SIGESCROW private key is printed to paper, and deleted from the machine after the identity has been added to the keyserver successfully.

Then Alice selects a pseudonym with a domain served by the keyserver and verifies that it has not been entered to the Hashchain yet by searching her local copy of the Hashchain. Alice then constructs the UIDMessage, signs it with both SIGKEY and SIGESCROW, and sends it to the keyserver using KeyRepository.CreateUID(). Her call is paid by a payment token.

The keyserver will verify the request and (on success) return a signed UIDMessageReply. Alice decrypts the UIDMessage in the UIDMessageReply and verifies the signature. She then waits for some time to allow other entries to be added to the Hashchain. In the meantime, Alice creates a number of KeyInit Messages for her new identity and publishes them on the keyserver's KeyInit repository via KeyInitRepository.AddKeyInit(). Her call is paid by a payment token.

She then updates her local Hashchain copy via KeyRepository.FetchHashChain() and verifies that her identity has been added to the Hashchain as demanded. Only then does she tell Bob about her new Identity.

Starting a session: Bob

On hearing about Alice's new Identity, Bob updates his local Hashchain copy via KeyRepository.FetchHashChain() and then searches it exhaustively for Alice's Identity. On finding the first entry, he then construct a cache of her signature keys and last UIDIndex.

Bob then fetches a single KeyInit message from the KeyInit Repository via KeyInitRepository.FetchKeyInit(). He verifies the reply to be valid and signed by Alice's SIGKEY.

He then constructs a message from the public key material received from the UIDMessage and KeyInit Message, adds the NymAddress from the KeyInit Message, adds his own keys and addresses valid only for this session, and sends it to the KeyInit MIXADDRESS.

In responding, Alice will not have to consult the keyserver with the exception of keeping the local hashchain copy current.