With Trusted Third Party-Version 1 Version 1: Alice A Bob n Authentication (n KA Center A,(nKA nKa Question:Is this authentication protocol secure? -Answer:No.Vulnerable to man-in-the-middle attacks. 66 With Trusted Third Party – Version 1  Version 1:  Question: Is this authentication protocol secure? ─ Answer: No. Vulnerable to man-in-the-middle attacks. Alice A Bob n {n}KA A, {n}KA {n}KB Authentication Center