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

This question was addressed to me in an interview for job.

My question is taken from Overview in chapter Cryptography Overview, TCP/IP and Communication Networks of Cryptograph & Network Security

Answer 1

The correct answer is (b) m(x)=x^8+x^4+x^3+x+1

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