Which of the following security-focused protocols has confidentiality services operating at a layer different from the others?
Correct Answer: A
Explanation/Reference:
Explanation:
S-HTTP provides application layer security, while the other protocols provide transport layer security.
Incorrect Answers:
B: FTPS can use SSL.
FTPS (also known as FTPES, FTP-SSL and FTP Secure) is an extension to the commonly used File Transfer Protocol (FTP) that adds support for the Transport Layer Security (TLS) and the Secure Sockets Layer (SSL) cryptographic protocols.
C: SSL can be used by FTPS. SSL provides transport layer security.
D: SPX is a transport layer protocol (layer 4 of the OSI Model).
References:
Stewart, James M., Ed Tittel, and Mike Chapple, CISSP: Certified Information Systems Security Professional Study Guide, 5th Edition, Sybex, Indianapolis, 2011, p. 856