Prospero supported limited security. Admins could connect to it, log in, create new users and perform other administrative operations with a web browser. It used HTTP for everything, however, and all its communications were in plain text. It also used plain text to talk to RabbitMQ.
Messages (POSTs) sent to it had to be signed with a symmetric key. Admins therefore had access to all the user keys and they are stored in plain text in the database.
Miranda is more serious about security. When the system is first installed a new certificate authority is created. This CA is used to sign the certificates that the various nodes present when they join the cluster.
All users have a key pair and to do anything, they must first create a session. The session is a random, 8 byte integer that is encrypted with the user's public key when it is handed back to the user.
All communication going into Miranda is encrypted using SSL/TLS. Communications coming out of Miranda depend on the subscription: it can be HTTP or HTTPS.