Signatures

A message can be sent in one of 3 "types/modes":

• origin a regular message send from a client account to another client account
• authorized a message sent on behalf of a client account but without access to the client's private key
• server a message send from a mail-server to a client

Verify Client

The signature check will differ based on the sending mode

• if the send type is "origin":
  • get the public key of the sender
  • hash the header (without signatures)
  • verify if the given client signature matches the header-hash (using: header hash, client signature, public key)
• if the send type is "authorized":

  • get the public key of the origin sender (this is actually the originator who we send on behalf)

  • get the public key of the AUTHORIZEDBY from the header

  • get the signature of the AUTHORIZEDBY from the header

  • verify if the signature matches (using: hash authorized public key, authorized signature, origin public key)

  • At this point, we have verified that the public key is valid, as it is signed with the origin public key

  • get the public key of the AUTHORIZEDBY

  • hash the header (without signatures)

  • verify if the given client signature matches the header hash (using: header hash, client signature, AUTHORIZEDBY public key)

• if the send type is "server":
  • get the public key of the sender as ROUTING (it's not a address hash, but a routing hash)
  • hash the header (without signatures)
  • verify if the given client signature matches the header-hash (using: header hash, client signature, ROUTING public key)

Verify Server

This will always verify the sending server. A sending server attaches a signature to prove it has originated from that specific server. In the future this could be amended with proxy servers in between (although communication should be end-to-end without proxies)

• if the send type is "server", the server verification is ignored. This is because it is the same signature as the client signature.
• if the send type is "origin":
  • get the public key of the sender
  • hash the header (without signatures)
  • verify if the given server signature matches the header-hash (using: header hash, server signature, public key)