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.

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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