# PDP schemes parameter generation

For the PDP scheme, I need to generate the following parameter: g is a generator of Q (Q is the set of quadratic residues modulo N (N = pq is the RSA modulus) What algorithm can be used to generate this parameter most effectively?

• All but answered there. – fgrieu May 14 '19 at 9:43
• To summarize the answer: pick $p, q$ to be distinct safe primes ($(p-1)/2, (q-1)/2$ are also prime), then pick an arbitrary $r$ and set $g = r^2 \pmod{pq}$; as long as $\gcd(pq, g-1) = 1$, then $g$ will generate the entire group. If you don't want to bother messing with $r$, you can just note that $g=4$ will work... – poncho May 14 '19 at 13:05