EBK COMPUTER NETWORKING
7th Edition
ISBN: 8220102955479
Author: Ross
Publisher: PEARSON
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Question
Chapter 8, Problem R6RQ
Program Plan Intro
Symmetric key encryption:
The Symmetric encryption uses a symmetric key, which is a series of numbers and letters. Then this symmetric key is used to encrypt a message as well as decrypt it.
Public key encryption:
A cryptographic system that uses two keys which are: one public key known to everyone and a private key known only to the message recipient.
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Students have asked these similar questions
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.
R6. Suppose N people want to communicate with each of N-1 other people using symmetric key
encryption. All communication between any two people, i and j, is visible to all other people in
this group of N, and no other person in this group should be able to decode their communication.
How many keys are required in the system as a whole? Now suppose that public key encryption
is used. How many keys are required in this case?
An old encryption system uses 20-bit keys. A cryptanalyst, who wants to brute-force attack theencryption system, is working on a computer system with a performance rate N keys per second.
How many possible keys will be available in the above encryption system?
What will be the maximum number of keys per second (N) that the computer system isworking with, if the amount of time needed to brute-force all the possible keys was 512 milliseconds? Show you detailed calculations.
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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- Alice and Bod have decided to use a symmetric encryption algorithm. They have some assumptions about their messages:- Messages only contain capital letters (i.e. A to Z)- The length of their shared key must be greater than or equal to the length of the plaintext- They assign each letter a number as follows: (A,0), (B,1), (C,2), (D,3),…, (Z,25)Their algorithm combines the key and the message using modular addition. The numerical values of corresponding message and key letters are added together, modulo 26. For example, if the plain text is “HELLO” and the key is “SECRET” then the encrypted message is calculated as following:Since the length of the plaintext is 5, we just need the first 5 letters of the key (i.e. “SECRE”), then for each letter, we should add corresponding letters in both the plaintext and the key modulo 26.Plaintext: H (7) E (4) L (11) L (11) O (14)Key: S (18) E (4) C (2) R (17) E(4)Cipher: Z (25) I (8) N(13) C(2) S (18) Write a program in Python, C/C++ or JavaScript to…arrow_forwardSuppose the two prime numbers p = 23 and q = 37 are used for an RSA encryption scheme. What are the values of the connection key n, the encryption e and the decryption key d, given that d < e? e = d =arrow_forwardLet's assume that Bob and Alice share a secret key in a symmetric key system. Bob wishes tobegin a conversation with Alice, and sends her a message that essentially says "let's talk". Aliceis suspicious that the person contacting her might not be Bob, so Alice generates a single-userandom number (a nonce) and sends it to Bob. Bob encrypts the nonce with the secret key heshares with Alice and sends it back. Alice decrypts this message and retrieves the same nonceshe sent to Bob. Which of the following is true, provided the secret key K has not been compromised?arrow_forward
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