University of Asia and the Pacific
For searching keywords against encrypted data, the Public key Encryption scheme with Keyword Search (PEKS), and it's an extension called Secure-Channel Free PEKS (SCF-PEKS) have been proposed. In SCF-PEKS, a receiver makes a trapdoor for a keyword, and uploads it on a server. A sender computes an encrypted keyword, and sends it to the server. The server executes the searching procedure (called the test algorithm, which takes as inputs an encrypted keyword, trapdoor, and secret key of the server).