Alice and Bob never meet, but they have the key to each other’s hearts.
Alice’s message is padded and obfuscated. The key is symmetric and truly random. No one detects the movement of the message from Alice to Bob. There is no metadata.
After being used once they destroy the key.
Bob then sends a similar message back to Alice (who waited impatiently, feeling faint in the sticky hot, hot, heat of a limpid summer evening). A different key was used, also symmetric, truly random, and obfuscated. It became non-existent after its useful life.
Mr. Schedoni, sitting between them, and jealous of their intimacy, did not even notice this deeply personal exchange. He slouched in his chair and wondered why it was such a quiet night.