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For this problem, solve by hand or write a program (perhaps in Python). If you write a program, please submit the code as a second submission file, as described above. Problem 2 ! This problem involves cryptanalyzing a Vigenère cipher, which you may read about on Wikipedia: https://en.wikipedia.org/wiki/Vigen%C3%A8re_cipher. Vigenère ciphers can generally be de- ciphered using Kasiski examination, which is discussed on the Wikipedia page. You can find some ciphertext produced with the Vigenère cipher under a certain key on our course website at: https://cseweb.ucsd.edu/classes/fa21/cse107-a/resources/hw1/ciphertext. We have also provided sample decryption code at: https://cseweb.ucsd.edu/classes/fa21/cse107-a/resources/hw1/decrypt.py. Encrypting a plaintext letter with a key letter A results in no change, encrypting with a key letter B results in an increment by one place in the alphabet, encrypting with a key letter C results in an increment by two places, and so on. Assume that the original plaintext contains only uppercase letters (A-Z) and no spaces or punctuation. For example, encrypting the plaintext ATTACKATDAWN with the key BLAISE results in the followwing

For this problem, solve by hand or write a program (perhaps in Python). If you write a program, please submit the code as a second submission file, as described above. Problem 2 ! This problem involves cryptanalyzing a Vigenère cipher, which you may read about on Wikipedia: https://en.wikipedia.org/wiki/Vigen%C3%A8re_cipher. Vigenère ciphers can generally be de- ciphered using Kasiski examination, which is discussed on the Wikipedia page. You can find some ciphertext produced with the Vigenère cipher under a certain key on our course website at: https://cseweb.ucsd.edu/classes/fa21/cse107-a/resources/hw1/ciphertext. We have also provided sample decryption code at: https://cseweb.ucsd.edu/classes/fa21/cse107-a/resources/hw1/decrypt.py. Encrypting a plaintext letter with a key letter A results in no change, encrypting with a key letter B results in an increment by one place in the alphabet, encrypting with a key letter C results in an increment by two places, and so on. Assume that the original plaintext contains only uppercase letters (A-Z) and no spaces or punctuation. For example, encrypting the plaintext ATTACKATDAWN with the key BLAISE results in the followwing

Computer Networking: A Top-Down Approach (7th Edition)
Computer Networking: A Top-Down Approach (7th Edition)
7th Edition
ISBN:9780133594140
Author:James Kurose, Keith Ross
Publisher:James Kurose, Keith Ross
Chapter1: Computer Networks And The Internet
Section: Chapter Questions
Problem R1RQ: What is the difference between a host and an end system? List several different types of end...
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For this problem, solve by hand or write a program (perhaps in Python). If you write a program, please submit the code as a second submission file, as described above. Problem 2 ! This problem involves cryptanalyzing a Vigenère cipher, which you may read about on Wikipedia: https://en.wikipedia.org/wiki/Vigen%C3%A8re_cipher. Vigenère ciphers can generally be de- ciphered using Kasiski examination, which is discussed on the Wikipedia page. You can find some ciphertext produced with the Vigenère cipher under a certain key on our course website at: https://cseweb.ucsd.edu/classes/fa21/cse107-a/resources/hw1/ciphertext. We have also provided sample decryption code at: https://cseweb.ucsd.edu/classes/fa21/cse107-a/resources/hw1/decrypt.py. Encrypting a plaintext letter with a key letter A results in no change, encrypting with a key letter B results in an increment by one place in the alphabet, encrypting with a key letter C results in an increment by two places, and so on. Assume that the original plaintext contains only uppercase letters (A-Z) and no spaces or punctuation. For example, encrypting the plaintext ATTACKATDAWN with the key BLAISE results in the following ciphertext: Plaintext АТТАСКАTDAWN Key Ciphertext BETIUOBEDIOR BLAISEBLAISE The goal for this part of the homework is to figure out what key was used to encrypt your ciphertext. (a) What is the key? (E, free to reference sections of your submitted code, but please write your explanation in clear English sentences. How did you recover the key? Explain your methodology at a high level. Feel
Transcribed Image Text:For this problem, solve by hand or write a program (perhaps in Python). If you write a program, please submit the code as a second submission file, as described above. Problem 2 ! This problem involves cryptanalyzing a Vigenère cipher, which you may read about on Wikipedia: https://en.wikipedia.org/wiki/Vigen%C3%A8re_cipher. Vigenère ciphers can generally be de- ciphered using Kasiski examination, which is discussed on the Wikipedia page. You can find some ciphertext produced with the Vigenère cipher under a certain key on our course website at: https://cseweb.ucsd.edu/classes/fa21/cse107-a/resources/hw1/ciphertext. We have also provided sample decryption code at: https://cseweb.ucsd.edu/classes/fa21/cse107-a/resources/hw1/decrypt.py. Encrypting a plaintext letter with a key letter A results in no change, encrypting with a key letter B results in an increment by one place in the alphabet, encrypting with a key letter C results in an increment by two places, and so on. Assume that the original plaintext contains only uppercase letters (A-Z) and no spaces or punctuation. For example, encrypting the plaintext ATTACKATDAWN with the key BLAISE results in the following ciphertext: Plaintext АТТАСКАTDAWN Key Ciphertext BETIUOBEDIOR BLAISEBLAISE The goal for this part of the homework is to figure out what key was used to encrypt your ciphertext. (a) What is the key? (E, free to reference sections of your submitted code, but please write your explanation in clear English sentences. How did you recover the key? Explain your methodology at a high level. Feel
{0, 1, ...,9}. Consider the symmetric encryption scheme in M[1]M[2]M[3]M[4] € Zfo is a four-digit string, a key T Perm(Z10) is a random permutation on Z10, and the ciphertext C = C[1]C[2]C[3]C[4] = E¬(M) E z{o is computed Problem 1 Let Z10 L which a message M as follows: Alg E(M) For i = 1,...,4 do P[i] + (M[i] + i) mod 10 C[i] + T(P[i]) Return C (a) Specify a decryption algorithm D such that SE = (K, E,D) is a symmetric encryp- tion scheme (Lecture 2 Slide 2) meeting the correct decryption requirement (Lecture 2 Slide 3). Is this scheme a substitution cipher as per the definition of Lecture 2 Slides 13, (b) 14? Why or why not? Is this encryption scheme perfectly secure as per the definition of Lecture 2 Slide (c) 47? Why or why not?
Transcribed Image Text:{0, 1, ...,9}. Consider the symmetric encryption scheme in M[1]M[2]M[3]M[4] € Zfo is a four-digit string, a key T Perm(Z10) is a random permutation on Z10, and the ciphertext C = C[1]C[2]C[3]C[4] = E¬(M) E z{o is computed Problem 1 Let Z10 L which a message M as follows: Alg E(M) For i = 1,...,4 do P[i] + (M[i] + i) mod 10 C[i] + T(P[i]) Return C (a) Specify a decryption algorithm D such that SE = (K, E,D) is a symmetric encryp- tion scheme (Lecture 2 Slide 2) meeting the correct decryption requirement (Lecture 2 Slide 3). Is this scheme a substitution cipher as per the definition of Lecture 2 Slides 13, (b) 14? Why or why not? Is this encryption scheme perfectly secure as per the definition of Lecture 2 Slide (c) 47? Why or why not?
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