Using RSA with p = 13, q = 5 and e = 7, the value of d and the cipher value of '6' with key (e, n) are

1. A7, 4
2. B7, 1
3. C7, 46
4. D55, 1

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Correct answer: C. 7, 46

Explanation

n = 65, φ(n) = 48. d = 7⁻¹ mod 48 = 7 (since 49 ≡ 1). C = 6⁷ mod 65: 6² = 36, 6⁴ ≡ 61, 6⁷ = 61 × 36 × 6 ≡ 46.