EBK COMPUTER NETWORKING
7th Edition
ISBN: 8220102955479
Author: Ross
Publisher: PEARSON
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Expert Solution & Answer
Chapter 8, Problem P12P
Explanation of Solution
- The following figure describes about the message authentication done between two different persons using encryption method.
- The message m is concatenated with S1 creating a hash code H(m, h) and the code is encrypted with S2 forming KS2(m, h).
- The encrypted code is sent to the receiver through internet...
Expert Solution & Answer
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Students have asked these similar questions
Exercise 1 (The RSA basics (
Alice forms a public key for the "textbook" RSA public-key encryption and signature schemes,
choosing N = 1073 and e = 715.
1. Encrypt the message M = 3 for Alice.
2. What is Alice's private key, and how does she use it for decrypting the received ciphertext?
3. Generate a signature on the message M = 1234567 using the following simple hash function
H: {0, 1} ZN such that H(M)= 3M + 5 (mod N).
4. Verify that the signature you generated in the previous step is a valid signature.
Assume there is a Certificate Authority (CA) with a well-known public key. Further assume every user is issued a certificate for his/her public key. For convenience, we use PKu and SKu to represent user’s public key and private key, respectively. Draw diagrams to answer the following questions. a) Suppose Alice wants to send a large secret message M to Bob. Describe how Alice should send M in an authenticated way. b) Assume Bob receives the message sent by Alice. Describe how Bob should process the message.
c) Suppose Alice needs to send a number of large secret messages to Bob. Alice would like to avoid signing digital signatures for all these messages. Develop a protocol for Alice and Bob so that all the messages can be sent in a confidential and authenticated way. Briefly describe the intuition of your protocol first and then draw a diagram.
. Q: There is no authentication in the Diffie-Hellman key-exchange protocol. By
exploiting this property, a malicious third party, Chuck, can easily break into
the key exchange taking place between Alice and Bob, and subsequently ruin
the security. Explain how this would work.
Chapter 8 Solutions
EBK COMPUTER NETWORKING
Ch. 8 - Prob. R1RQCh. 8 - Prob. R2RQCh. 8 - Prob. R3RQCh. 8 - Prob. R4RQCh. 8 - Prob. R5RQCh. 8 - Prob. R6RQCh. 8 - Prob. R7RQCh. 8 - Prob. R8RQCh. 8 - Prob. R9RQCh. 8 - Prob. R10RQ
Ch. 8 - Prob. R11RQCh. 8 - Prob. R12RQCh. 8 - Prob. R13RQCh. 8 - Prob. R14RQCh. 8 - Prob. R15RQCh. 8 - Prob. R16RQCh. 8 - Prob. R17RQCh. 8 - Prob. R18RQCh. 8 - Prob. R19RQCh. 8 - Prob. R20RQCh. 8 - Prob. R21RQCh. 8 - Prob. R22RQCh. 8 - Prob. R23RQCh. 8 - Prob. R24RQCh. 8 - Prob. R25RQCh. 8 - Prob. R26RQCh. 8 - Prob. R27RQCh. 8 - Prob. R28RQCh. 8 - Prob. R29RQCh. 8 - Prob. R30RQCh. 8 - Prob. R31RQCh. 8 - Prob. R32RQCh. 8 - Prob. R33RQCh. 8 - Prob. P1PCh. 8 - Prob. P2PCh. 8 - Prob. P3PCh. 8 - Prob. P4PCh. 8 - Prob. P5PCh. 8 - Prob. P6PCh. 8 - Prob. P8PCh. 8 - Prob. P12PCh. 8 - Prob. P13PCh. 8 - Prob. P14PCh. 8 - Prob. P18PCh. 8 - Prob. P20PCh. 8 - Prob. P21PCh. 8 - Prob. P22PCh. 8 - Prob. P23P
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Similar questions
- Computer Science * Alice and Bob are conducting Diffie-Hellman key exchange with the parameters p = 101 and a = 2. Their parameters are small and we decide to crack the key exchange. Suppose Alice is observed sending public key A = 79 and Bob sends public key B = 26. a) What is Alice's private key? b) What is Bob's private key? c) What is the shared secret? Alice and Bob are using the EIGamal cipher with the parameters p = 29 and a = 2. %3D Their parameters are small and we decide to crack the cipher. Suppose Alice is observed sending public ephemeral key kE 25 and Bob sends public key 3 = 4. %3D Alice is observed transmitting the ciphertext y = 13. a) What is the masking key kM? b) What is the plaintext?arrow_forwardsuppose the RSA cryptosystem is used for sending secret messages with the private key (15,3) and the cipher text "4" is received. what is the plaintext?arrow_forwardA shortcoming of using an elliptic curve E(Fp) for cryptography is the fact that it takes two coordinates to specify a point in E(Fp). However, as discussed briefly at the end of Sect. 6.4.2, the second coordinate actually conveys very little additional information.(b) Alice and Bob decide to use the prime p = 1123 and the elliptic curveE : Y2 = X3 + 54X + 87.Bob sends Alice the x-coordinate x = 278 and the bit β = 0. What point is Bob trying to convey to Alice? What about if instead Bob had sent β = 1?arrow_forward
- Suppose that Alice and Bob communicate using ElGamal cipher and f (p. 9. Z) is common public values. Bob generates his private key d ER Z and then computes the corresponding and public public key y=g" (mod p). To save time, Bob uses the same number r each time he encrypts a plaintext message m (ie., r is a fixed nonce of Bob, and it is not randomly generated each time encryption is performed). Assume that Alice compute the ciphertext for the message m as (cc) = (g mod p, mxy mod p). and for the message m as (1,2)=(g" mod p, xy' mod p). Show how an adversary who possesses a plaintext-ciphertext pair (m. (c.ca)) can decrypt (1, 2) without knowing the private key d of Bob.arrow_forward4. In the RSA public-key encryption scheme, each user has a public key, e, and a private key, d. Suppose Bob leaks his private key. Rather than generating a new modulus, he decides to generate a new public and a new private key. Is this safe?arrow_forwardigital Signature using the RSA algorithm: Alice is sending an integer value mA = 3 to Bob with RSA signing. Alice's public key and private key are (5, 14) and (11, 14). Alice first releases her public key to public. How to calculate the signature sig(mA).arrow_forward
- Cryptography: Alice and Bob are going to establish a secure session key utilizing Diffie-Hellman key exchange. The agreed upon public prime is, 10477, Alice’s secret is 997, Bob’s secret is 1137. The public base is 31. What is their session key?arrow_forwardQuestion 2: You are Alice. Bob publishes his ElGamal public key (q, a, ya) = (101, 2, 14). You desire to send the secret message “CALL ME” to Bob. Using the equivalence A = 01, B = 02, and so on up to Z = 26, you encode the message into the number 03 01 12 12 13 05. Regarding each of these two-digit numbers as a plaintext block, compute the message that you will send to Bob using his public key. This requires you to pick a “random” number k; use k = 32. You are Bob. You get a message from Alice. You like Alice a lot, so you are eager to read the message. Use your secret key (101, 2, 10) to decrypt Alice’s message. Notice that you don’t need to know what value of k Alice used in order to do this.arrow_forwardConsider an RSA key set for Alice with p = 23, q = 17, n = 391 and e = 15.a) Her public key is (e, n) = (15, 391). Is her private key (d, n) = (47, 391)? JusVfy your answer. b) Suppose Bob wants to encrypt a message 90 for Alice using RSA keys for confidenVality. Whatis the corresponding cipher text?Justify your answer.arrow_forward
- Alice uses RSA to send a key to Bob for use in encryption of future messages. The key is the word "CINEMA" and the encoding from letters to numbers is done using the ASCII: A = 65... Z = 90, space = 99. The public parameters (n, e) = (9379, 11) are shared. Encrypt Alice's key word, using 2-letter blocks. Please show work.arrow_forwardSuppose Alice and Bob performs the Diffie-Hellman key exchange, using the public parameters with prime p=11 and primitive element α=2 . Alice chooses her secret x A =2 and Bob chooses his secret x B =8 . What does Alice send to Bob? (Enter only a number in the box.) What is the key that Bob and Alice agree on? (Enter only a number in the box.)arrow_forwardConsider an RSA key set for Alice with p = 23, q = 17, n = 391 and e = 15.a) Her public key is (e, n) = (15, 391). Is her private key (d, n) = (47, 391)? Justffy your answer. b) Suppose Bob wants to encrypt a message 90 for Alice using RSA keys for confidenVality. Whatis the corresponding cipher text?Justify your answer.arrow_forward
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