Knowing a password to Keykos user name and connecting to Tymnet allowed one to exchange ASCII messages with an agent. The agent would do anything in could with the capabilities that it held on your behalf. The only other capabilities it held were a few supporting its own construction. Your instructions were at the key invocation level. Such an agent is created along with a new user name and password. It lasts indefinitely thru many terminal sessions. Part of the agent is a mutable “record collection” which is merely a map from ASCII names to capabilities. Perhaps the most frequently used command is the key invocation command. This would create and send just those messages that a program with the same capabilities could send.
This access was over unencrypted links. It was only the beginning of the era of a computer at the user end that could encrypt.