Question

Which function can be used in AES multiplication

(a) m(x)=x^7+x^4+x^3

(b) m(x)=x^8+x^4+x^3+x+1

(c) m(x)=x^8+x^3+x^2+x+1

(d) m(x)=x^8+x^5+x^3+x

The question was posed to me by my school teacher while I was bunking the class.

This intriguing question comes from The AES Algorthm in division Advanced Encryption Algorithm and Block Cipher Operation of Cryptograph & Network Security

Answer 1

Correct choice is (b) m(x)=x^8+x^4+x^3+x+1

To explain I would say: m(x)=x^8+x^4+x^3+x+1 stands for 100011011 which is an irreducible polynomial. Others are not irreducible polynomials.