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1. Describe an algorithm for the decryption process for a ciphertext input c = (m,, m,+1). You should use a notation similar to the encryption procedure as described above. 2. Draw a figure for your decryption algorithm.

1. Describe an algorithm for the decryption process for a ciphertext input c = (m,, m,+1). You should use a notation similar to the encryption procedure as described above. 2. Draw a figure for your decryption algorithm.

Database System Concepts
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
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Cryptography. Can you do question 1 & 2 please
Consider a Feistel cipher with r rounds and n = 128 (half the block length); = 256 (the key bit size). Then M = {0, 13256 (the plaintext space), C = {0, 11256 (the ciphertext space), and X= {0, 13256 (the key space). A key scheduling algorithm determines subkeys k₁, k₂ from a key KEK = {0, 13256. Each subkey k, determines a function f {0, 1128 {0, 1}128. Encryption takes r rounds: : Plaintext is m = (mo, m₁) with mo, m₁ = {0, 1}128, Round 1: (mo, m₁)→ (m₁, m₂) with m₂ = mo fi(m₁). Round 2: (m₁, m₂)→ (m2, m3) with m3 = m₁ + f₂(m₂). ⠀ Round r: (m,-1, m,) → (mr, mr+1) with mr+1 = mr-1 fr (m₂). The ciphertext is c = (mr, mr+1). For the Feistel cipher described above: 1. Describe an algorithm for the decryption process for a ciphertext input c = -(m,, m,+1). You should use a notation similar to the encryption procedure as described above. 2. Draw a figure for your decryption algorithm.
Transcribed Image Text:Consider a Feistel cipher with r rounds and n = 128 (half the block length); = 256 (the key bit size). Then M = {0, 13256 (the plaintext space), C = {0, 11256 (the ciphertext space), and X= {0, 13256 (the key space). A key scheduling algorithm determines subkeys k₁, k₂ from a key KEK = {0, 13256. Each subkey k, determines a function f {0, 1128 {0, 1}128. Encryption takes r rounds: : Plaintext is m = (mo, m₁) with mo, m₁ = {0, 1}128, Round 1: (mo, m₁)→ (m₁, m₂) with m₂ = mo fi(m₁). Round 2: (m₁, m₂)→ (m2, m3) with m3 = m₁ + f₂(m₂). ⠀ Round r: (m,-1, m,) → (mr, mr+1) with mr+1 = mr-1 fr (m₂). The ciphertext is c = (mr, mr+1). For the Feistel cipher described above: 1. Describe an algorithm for the decryption process for a ciphertext input c = -(m,, m,+1). You should use a notation similar to the encryption procedure as described above. 2. Draw a figure for your decryption algorithm.
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