Question: Consider the following protocol, designed to let A and B decide on a fresh, shared session key K AB . We assume that they already

Consider the following protocol, designed to let A and B decide on a fresh, shared session key K′_AB. We assume that they already share a long-term key K_AB. 1. AB:A, NA. 2. BA:E(KAB, [NA, KAB]) 3. AB:E(KAB, NA)

a. We first try to understand the protocol designer’s reasoning:
—Why would A and B believe after the protocol ran that they share K′_AB. with the other party?
—Why would they believe that this shared key is fresh?
In both cases, you should explain both the reasons of both A and B, so your answer should complete the sentences A believes that she shares with K′_ABB since...
B believes that he shares with K′_ABB since...

A believes that K′_ABis fresh since...

B believes that K′_ABis fresh since...

b. Assume now that A starts a run of this protocol with B. However, the connection is intercepted by the adversary C. Show how C can start a new run of the protocol using reflection, causing A to believe that she has agreed on a fresh key with B (in spite of the fact that she has only been communicating with C).Thus, in particular, the belief in (a) is false.

c. Propose a modification of the protocol that prevents this attack.

1. AB:A, NA. 2. BA:E(KAB, [NA, KAB]) 3. AB:E(KAB, NA)

Step by Step Solution

★★★★★

3.30 Rating (153 Votes )

There are 3 Steps involved in it

1 Expert Approved Answer

Step: 1 Unlock

a A believes that she shares K AB with B since her nonce came back in message 2 encrypted with a key ... View full answer

Question Has Been Solved by an Expert!

Get step-by-step solutions from verified subject matter experts

Step: 2 Unlock

Step: 3 Unlock

Students Have Also Explored These Related Cryptography And Network Security Questions!

Consider the following protocol, designed to let A and B decide on a fresh, shared session key, Ks. We assume that they already share a long-term key, KAB. 1. A -> B: A, NA 2. B -> A: E(KAB,...

Planning is one of the most important management functions in any business. A front office managers first step in planning should involve determine the departments goals. Planning also includes...

The Crazy Eddie fraud may appear smaller and gentler than the massive billion-dollar frauds exposed in recent times, such as Bernie Madoffs Ponzi scheme, frauds in the subprime mortgage market, the...

Consider the following protocol, designed to let A and B decide on a fresh, shared session key K'_AB. We assume that they already share a long-term key K_AB. 1. A rightarrow B: A, N_A. 2. B...

Problem 14.6 on pp 448-449 of the textbook (Cryptography-and-Network-Security-Principles-and-Practice-6th-Edition) 14.6 Consider the following protocol, designed to let A and B decide on a fresh,...

on Consider the following protocol designed so that X and Y will decide on fresh secret key Kf. It is assumed that they have previously shared an initial key K'. X->Y: IDX, N1, where N1 is a nonce...

Q4) Consider the following protocol designed so that I and M will decide on fresh secret key, K_fresh. It is assumed that they have previously shared an initial key, K_initial. T->M: IDE, N1, N1 is a...

1 Protocol Analysis In lecture we have looked at some different vulnerable (e.g., Diffie-Hellman, NeedhamSchroeder) and improved (e.g., Diffie-Hellman with signing, Otway-Rees) protocols. For this...

EchoServer.java import java.net.*; import java.util.*; class EchoServer { public static void main( String args[] ) throws Exception { DatagramSocket socket = new DatagramSocket(1500); DatagramPacket...

Objectives On completion of this assignment you should be able to: Understand some basic techniques for building a secure channel. Understand network programming, Write (Java or C/C++) UDP programs...

Prove that the collection F(N) of all finite subsets of N is countable.

Write a c program to implement a double-linked list that has 5 nodes if your last digit of id is in between 0-4 otherwise 7 nodes. Users can input only even numbers in this linked list.

Q# 1 . A company currently pays a dividend of $ 5 . 0 per share ( i . e . , D 0 = $ 5 ) . It is estimated that the company's dividend will grow at a rate of 2 5 % per year for the next 3 years, and...

1. Describe the challenges inherent in service innovation and design.

Give a reason for the use of guard bits.

What are the four essential elements of a number in floating-point notation?

Consider the following operation on a binary word. Start with the least significant bit. Copy all bits that are 0 until the first bit is reached and copy that bit, too. Then take the complement of...

In this module, you explored policies and practices used by organizations to protect information. There are a variety of policies that are intended to improve the security posture of an organization....

Exercise 5-11 Accounting for notes receivable LO 5-4 Poole Enterprises loaned $25,000 to Boyd Co. on September 1, 2014, for one year at 6 percent interest. Required Show the effects of the following...

29. Brown Company's bank statement for September 30 showed a cash balance of s1,350. The company's Cash account in its general ledger showed a $995 debit balance. The following information was also...