Step:
RSA Algorithm:
1) Calculate value of n = p × q, where p and q are prime no.’s
2) calculate Ø(n) = (p-1) × (q-1)
3) consider d as public key such that Ø(n) and d has no common factors.
4) consider e as private key such that (e × d) mod Ø(n) = 1
5) Cipher text c = message i.e. md mod n
6) message = cipher text i.e. ce mod n
Calculation
Given p =13, q= 17, d = 35
Use step 2 and 4 of RSA algorithm to calculate private key.
Ø(n) = (13 – 1) × (17 – 1) = 12 × 16 = 192
Now,
(e × d) mod Ø(n) = 1
(e × 35) mod 192 = 1
e = 11
So, private key of A = 11