Q33,paper 2,j13. Using data p=3, q=11, n=pq, d=7 in RSA algorithm find the cipher text of the given plain text SUZANNE

Using data p=3, q=11, n=pq, d=7 in

RSA algorithm find the cipher text of

the given plain text SUZANNE

(A) BUTAEEZ

(B) SUZANNE

(C) XYZABCD

(D) ABCDXYZ.

Answer A.

Explanation

N=pxq.

N=33.

Phi= (p-1)x(q-1) =20.

Choose d and e such that both are co prime.

Choose e such that 1 < e < phi  and e and n are coprime. Let d=7 .

Compute a value for e such that (d * e) % phi = 1. One solution is e = 3 [(3 * 7) % 20 = 1] so e =3

Ciphertext =(plaintext)³mod n.

S position is 19 th so it can be.

(19*19*19)mod 33= 6859-6831=28

28 th position is of B.

Hence answer is option A.