When using pppd which authentication protocol is the most secure? 06/14/2017 – by Mod_GuideK 0 When using pppd which authentication protocol is the most secure? A. clear text B. PAP C. CHAP D. LAP SHOW ANSWERSCorrect Answer: C Explanation/Reference: Explanation: PAP sends all information as clear text. CHAP sends all information as encrypted text. Download Printable PDF. VALID exam to help you PASS.