Question

For p = 11 and q = 19 and choose d=17. Apply RSA algorithm where Cipher message=80 and thus find the plain text.

(a) 54

(b) 43

(c) 5

(d) 24

This question was addressed to me in an interview.

This interesting question is from Knapsack/ Merkle in chapter Public Key Cryptography and RSA of Cryptograph & Network Security

Answer 1

Right option is (c) 5

Explanation: n = pq = 11 × 19 = 209.

                            C=M^e mod n ;  C=5^17 mod 209 ; C = 80 mod 209.