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. 6
6 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
Attacks on Version 1 with 3rd Party Man-in-the-middle attack I am Robert I am Alice Alice Robert Bob A n Authentication Center A,(nika (nKB How to defend against this attack? -Solution:add principal name to prevent (n}k from being reused by attacker. 7
7 Man-in-the-middle attack How to defend against this attack? ─ Solution: add principal name to prevent {n}KA from being reused by attacker. Alice Bob A n {n}KA A, {n}KA {n}KB Authentication Center Robert A n {n}KA Attacks on Version 1 with 3rd Party I am Robert I am Alice