New answers tagged chosen-ciphertext-attack
1
I'll assume this is not homework.
It's actually quite simple:
Pick a random value $r$
Compute $s = r^2 \bmod n$, and submit $s$ to the Rabin decryptor
Since $s$ is a Quadratic Residue, the Rabin decryptor will return some value $t = \sqrt{s} \bmod n$.
Now, $s$ has four square roots (assuming $n$ has two prime factors and you didn't happen to pick an $r$ ...
Top 50 recent answers are included