On 19/09/16 18:36, Walter Ray-Dulany wrote: <snip/> > Let's see what we've got. > > ( (16**12)*(7**15) ) mod 225 = 208. > > I will leave it as an exercise to check that the decryption of 208 is in > fact 12.
I like a challenge :-) So we got to p=3, q=5, and my encrypted value c=208. Following the Wideskies Pallier decryption algorithm, Step (2): N = p * q = 15 lambda(N) = lcm(p-1,q-1) = 4 Step (3): mu = lambda(N) modinverse N = 4 Step (4): c' = c^lambda(N) mod N^2 = 208^4 mod 225 = 46 Step(5): m' = L(c') = ((c' - 1) / N) mod N = (45 / 15) mod 15 = 3 Step(6): m = (m' * mu) mod N = 12 yay! The fog is slowly clearing, though I'm totally baffled about how I can pick a random zeta during encryption, and it plays no part in the decryption. Regards, Tim