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In a RSA cryptosystem, a participant A uses two prime numbers p = 13 and q =17 to generate her public and private keys. If the public key of A is 35, then the private key of A is ________.
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- 21
- 11
- 31
- 121
Correct Option: B
As given data P = 13, q = 17, e = 35, d = ?
As per RSA Algorithm.
n = P × q = 13 × 17 = 221
By using RSA formula ,
φ(n) = (P – 1) (q – 1) = 12 × 16 = 192.
To find out the private key of A, then take Modulas operater for RSA formula.
(d × e) mod φ(n) = 1
(d × 35) mod (192) = 1
d = 11, Hence, answer is 11.
