Consider 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 = (P + Ko) 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?
Consider 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 = (P + Ko) 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?
Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
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![2 Consider 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?](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fa0096840-9b7a-43a2-b949-2a26be038979%2F50a282f0-ef63-42ba-aa53-3d77545f5883%2Ffz2s78o_processed.jpeg&w=3840&q=75)
Transcribed Image Text:2 Consider 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?
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