Question

The public key of given user, in an RSA encryption system is e = 57 and n = 3901. What is the value of  Euler’s totient function ϕ(n) for calculating the private key of the user?

(a) 4369

(b) 3772

(c) 871

(d) 7892

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Answer 1

The correct choice is (b) 3772

To elaborate: Given that n=3901 and e=31. We know that n = p∗q where p and q are prime numbers, which gives 3901 = 47*83. Now, ϕ(n) is Euler’s totient function i.e., ϕ(n) = (p−1)∗(q−1)

ϕ(n) = (47−1)∗(83−1)

ϕ(n) = 46*82 = 3772.