These source files let you use the SecretHandshake protocol (see parent directory) with the awesome Cap’n Proto RPC library.
SecretRPC provides high-level RPC client and server classes that mimic Cap’n Proto’s EzRpcClient/Server classes, but use SecretConnection (q.v.)
If you currently use Cap'n Proto EzRpc you should be able to drop in SecretRPC pretty easily. You’ll just need to use the SecretKey class to generate a key-pair, and persist it somehow. (Hint: put the secret key someplace secure, like the Mac/iOS Keychain.)
SecretConnection is lower-level: it exposes a StreamWrapper class that takes a Cap’n Proto AsyncIoStream and returns a new AsyncIoStream that internally performs the SecretHandshake and the SecretStream encryption.
If you use lower-level Cap’n Proto classes to create connections, you’ll need to use the classes in SecretConnection to wrap your plain-TCP AsyncIOStream with the secure one. You can look at the code in SecretRPC.cc for clues.