
Computer Networking: A Top-Down Approach (7th Edition)
7th Edition
ISBN: 9780133594140
Author: James Kurose, Keith Ross
Publisher: PEARSON
expand_more
expand_more
format_list_bulleted
Question
Consider an 8-bit block cipher. How many possible input blocks does this cipher have? How many possible mappings are there? If we view each mapping as a key, then how many possible keys does this cipher have?
Expert Solution

This question has been solved!
Explore an expertly crafted, step-by-step solution for a thorough understanding of key concepts.
This is a popular solution
Trending nowThis is a popular solution!
Step by stepSolved in 2 steps

Knowledge Booster
Similar questions
- The hacker group Desdeia tries to break our old weak cipher which we used for the communication with the Duchess of Ligovia. It's generally known that an actual breaking of the cipher needs the reviewing a huge amount of variants which probably lasts a couple of months. Additionally we know that the reviewing of different variants needs always the same server resource. Using our intelligence sources we tried to get some information about the actual progress of breaking, but we got only some fragments: • The hacker group Desdeia uses for breaking their powerful four-core server which resources are fully dedicated to breaking process. . The actual breaking process began exactly at noon, but we don't know, on which day. . By the noon of 2nd of April, already 648,467,673 variants were successfully reviewed. Exactly at this noon, when the breaking process was already lasted for 19 days, it was attempted to double the server speed. The doubling itself was failed, but instead of it there was…arrow_forwardConsider the affine cipher f(p) = 3p+4 (mod 26), where p is the plaintext representation of the character under consideration. For example the plaintext of the letter A is 0, B is 1, C is 2, ... Z is 25. Use this cipher to encrypt the letters I, N, G, R (changing the numbers back to letters at the end.arrow_forwardThe definition of a Shift Cipher can be expressed as follows:Def. Let x, y, k ∈ Z26 with the encryption operation as ek(x) ≡ x + k mod 26 and thedecryption operation as dk(y) ≡ y - k mod 26.Given the provided letter encoding, what would be the encoding of the plaintext word ATTACKafter applying a shift cipher with a k=17?arrow_forward
- Let k be the encipherment key for a Caesar cipher. The decipherment key is 26 – k.One of the characteristics of a public key cryptosystem is that the encipherment anddecipherment keys are different. Explain why the Caesar cipher is a secret keycryptosystem, not a public key cryptosystem?arrow_forwardConsider a very simple symmetric block encryption algorithm in which 32-bits blocks of plaintext are encrypted using a 64-bit key. Encryption is defined as C = (PK₁) K₁ where C = ciphertext, K = secret key, Ko = leftmost 64 bits of K, K₁ = rightmost 64 bits of K,+ = bitwise exclusive OR, and is addition mod 264. a. Show the decryption equation. That is, show the equation for P as a function of C, Ko, and K₁. b. Suppose and adversary has access to two sets of plaintexts and their correspond- ing ciphertexts and wishes to determine K. We have the two equations: C = (PK) K₁; C = (PK) K₁ First, derive an equation in one unknown (e.g., Ko). Is it possible to proceed fur- ther to solve for Ko?arrow_forwardLet E'(T,X) be a tweakable block cipher that has already been keyed. Given plaintext P = P1 || P2 || ... || Pn (ie, P is an n-block plaintext). Ci = E'(i, Pi) for i=1..nsum = P1 xor P2 xor ... xor Pntag = E'(0,sum) For simplicity let's say that E'(T,X) = ROTL(X,T+1) (ie, X rotated left T+1 bits. If the block cipher block size is 8 bits and you are encrypting the two byte plaintext 67 89, what ciphertext and tag would be created? Fill in each box as a two-digit hex value. C1____? C2____? tag____?arrow_forward
- 4. Choose any 1 cipher methods of your choice and explain its working with examplearrow_forwardIn this problem we explore the relationship between password length and cryptographic security. Suppose a password consists of 77 ASCII characters. You can review the ASCII characters here.. Exactly 27=12827=128 of these codes are for printable characters; we will assume every character in the password is printable. What is the size of the keyspace that consists of passwords of this form?What is the equivalent key length in bits? Assuming that you could check one password every 10−810−8 seconds, what is the worst case running time for cracking this password by brute force search (in days)? Now assume that the user used only 3131 characters from the keyboard. What is the key length in bits in this case? How many days, in the worst case, would it take to break this weaker password? You can't round to the nearest day here -- be as exact as possible. Supposing you used only 3131 characters, how long is the shortest password that achieves 252252 bits of security?arrow_forwardThe security of asymmetric ciphers is based on the asymmetric operations, meaning operations that can not be easily reversed. What kind of asymmetric operations have you learned from this chapter? Can you propose some asymmetric operations?arrow_forward
- If an encryption function er is identical to the decryption function dg, then the key K is said to be an involutory key. (a) Let K = (a, b) be a key in an affine cipher over Z/nZ. Show that K is an involutory key if and only if a- = a (mod n) and b(a+1) = 0 (mod n).arrow_forwardIn this problem we explore the relationship between password length and cryptographic security. Suppose a password consists of 6 ASCII characters. You can review the ASCII characters here.. There are exactly 2' = 128 ASCII characters; we will assume every character in the password is ASCII (non-printing characters are allowed). What is the size of the keyspace that consists of passwords of this form? What is the equivalent key length in bits? Assuming that you could check one password every 10-" seconds, what is the worst case running time for cracking this password by brute force search (in days)?| Now assume that the user used only 28 characters from the keyboard. What is the key length in bits in this case? How many days, in the worst case, would it take to break this weaker password? You can't round to the nearest day here be as exact as possible. Supposing you used only 28 characters, how long is the shortest password that achieves 248 bits of security?arrow_forwardEach of the following is a true/false statement about a tweakable block cipher (TBC). Place a checkmark next to each true statement. In the questions mentioning E', let E' be a random instance of a TBC and E'(T,X) be the result of using E' with tweak T and input X. Group of answer choices: (1)For TBC security both the current key and tweak in use must be kept secret from adversaries. (2)Each time a new tweak is given to a TBC, the TBC behaves like a new random permutation. (3)When a TBC is used once per tweak its outputs may be considered (4)A TBC is a prominent part of the design of OCB. (5)If X1 ≠ X2, then always E'(T,X1) ≠ E'(T,X2) (6)If T1 ≠ T2, then always E'(T1,X) ≠ E'(T2,X)arrow_forward
arrow_back_ios
SEE MORE QUESTIONS
arrow_forward_ios
Recommended textbooks for you
- Computer Networking: A Top-Down Approach (7th Edi...Computer EngineeringISBN:9780133594140Author:James Kurose, Keith RossPublisher:PEARSONComputer Organization and Design MIPS Edition, Fi...Computer EngineeringISBN:9780124077263Author:David A. Patterson, John L. HennessyPublisher:Elsevier ScienceNetwork+ Guide to Networks (MindTap Course List)Computer EngineeringISBN:9781337569330Author:Jill West, Tamara Dean, Jean AndrewsPublisher:Cengage Learning
- Concepts of Database ManagementComputer EngineeringISBN:9781337093422Author:Joy L. Starks, Philip J. Pratt, Mary Z. LastPublisher:Cengage LearningPrelude to ProgrammingComputer EngineeringISBN:9780133750423Author:VENIT, StewartPublisher:Pearson EducationSc Business Data Communications and Networking, T...Computer EngineeringISBN:9781119368830Author:FITZGERALDPublisher:WILEY

Computer Networking: A Top-Down Approach (7th Edi...
Computer Engineering
ISBN:9780133594140
Author:James Kurose, Keith Ross
Publisher:PEARSON

Computer Organization and Design MIPS Edition, Fi...
Computer Engineering
ISBN:9780124077263
Author:David A. Patterson, John L. Hennessy
Publisher:Elsevier Science

Network+ Guide to Networks (MindTap Course List)
Computer Engineering
ISBN:9781337569330
Author:Jill West, Tamara Dean, Jean Andrews
Publisher:Cengage Learning

Concepts of Database Management
Computer Engineering
ISBN:9781337093422
Author:Joy L. Starks, Philip J. Pratt, Mary Z. Last
Publisher:Cengage Learning

Prelude to Programming
Computer Engineering
ISBN:9780133750423
Author:VENIT, Stewart
Publisher:Pearson Education

Sc Business Data Communications and Networking, T...
Computer Engineering
ISBN:9781119368830
Author:FITZGERALD
Publisher:WILEY