is not the only polynomial that gives GF(28) (see the last part of this question). n this question, you will learn the extended Euclidean algorithm for polynomials. A brief description of this algorithm is given below. Compute the following elements of Z₂[x] (mod x8 + x² + x³ + x + 1); your olynomials must be polynomials of degree at most 7.

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
icon
Related questions
Question




(mod
(4) This question deals with the finite field GF(28), which can be obtained as Z₂[x]
x³+x²+x³+x+1). This is the polynomial the AES cryptosystem uses, but
it is not the only polynomial that gives GF(28) (see the last part of this question).
In this question, you will learn the extended Euclidean algorithm for polynomials.
A brief description of this algorithm is given below.
Compute the following elements of Z₂[x] (mod x³ + x² + x³ + x + 1); your
polynomials must be polynomials of degree at most 7.
(a) (x² + x³ + x² + x²) (x³ + x + 1).
(b) (x³ + x² + 1) + (x³ + x²)
(c) (x² + x + 1) − (x² + x + 1).
(d) (x² + x)(x³ + 1)−¹ (I could have also written this as (x² + x)/(x³ + 1)).
To compute (x³ + 1)−¹ in GF(28), we proceed as in the case of integers.
Step 1. First compute the gcd(x³+1, x³+x²¹+x³+x+1). Here use the Euclidean
algorithm for polynomials. Each step in the Euclidean algorithm is a
long division of polynomials with remainder. At every step, just make
sure that the remainder has a degree less than that of the divisor.
Step 2. As in the case of integers, trace your steps back and find polynomials
s(x) and t(x) such that
(x³ + 1)s(x) + (x³ + x² + x³ + x + 1)t(x) = gcd(x³ + 1, x³ + x² + x³ + x + 1).
(e) GF(28) can also be obtained as Z₂[x] (mod x³ + x² + x6 +x+1). Under this
new polynomial, compute again Parts (a) and (c).
Transcribed Image Text:(mod (4) This question deals with the finite field GF(28), which can be obtained as Z₂[x] x³+x²+x³+x+1). This is the polynomial the AES cryptosystem uses, but it is not the only polynomial that gives GF(28) (see the last part of this question). In this question, you will learn the extended Euclidean algorithm for polynomials. A brief description of this algorithm is given below. Compute the following elements of Z₂[x] (mod x³ + x² + x³ + x + 1); your polynomials must be polynomials of degree at most 7. (a) (x² + x³ + x² + x²) (x³ + x + 1). (b) (x³ + x² + 1) + (x³ + x²) (c) (x² + x + 1) − (x² + x + 1). (d) (x² + x)(x³ + 1)−¹ (I could have also written this as (x² + x)/(x³ + 1)). To compute (x³ + 1)−¹ in GF(28), we proceed as in the case of integers. Step 1. First compute the gcd(x³+1, x³+x²¹+x³+x+1). Here use the Euclidean algorithm for polynomials. Each step in the Euclidean algorithm is a long division of polynomials with remainder. At every step, just make sure that the remainder has a degree less than that of the divisor. Step 2. As in the case of integers, trace your steps back and find polynomials s(x) and t(x) such that (x³ + 1)s(x) + (x³ + x² + x³ + x + 1)t(x) = gcd(x³ + 1, x³ + x² + x³ + x + 1). (e) GF(28) can also be obtained as Z₂[x] (mod x³ + x² + x6 +x+1). Under this new polynomial, compute again Parts (a) and (c).
Expert Solution
trending now

Trending now

This is a popular solution!

steps

Step by step

Solved in 2 steps with 3 images

Blurred answer
Knowledge Booster
Time complexity
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, computer-science and related others by exploring similar questions and additional content below.
Similar questions
  • SEE MORE QUESTIONS
Recommended textbooks for you
Database System Concepts
Database System Concepts
Computer Science
ISBN:
9780078022159
Author:
Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:
McGraw-Hill Education
Starting Out with Python (4th Edition)
Starting Out with Python (4th Edition)
Computer Science
ISBN:
9780134444321
Author:
Tony Gaddis
Publisher:
PEARSON
Digital Fundamentals (11th Edition)
Digital Fundamentals (11th Edition)
Computer Science
ISBN:
9780132737968
Author:
Thomas L. Floyd
Publisher:
PEARSON
C How to Program (8th Edition)
C How to Program (8th Edition)
Computer Science
ISBN:
9780133976892
Author:
Paul J. Deitel, Harvey Deitel
Publisher:
PEARSON
Database Systems: Design, Implementation, & Manag…
Database Systems: Design, Implementation, & Manag…
Computer Science
ISBN:
9781337627900
Author:
Carlos Coronel, Steven Morris
Publisher:
Cengage Learning
Programmable Logic Controllers
Programmable Logic Controllers
Computer Science
ISBN:
9780073373843
Author:
Frank D. Petruzella
Publisher:
McGraw-Hill Education