Consider the following variant of el gamal encryption. let p = 2q + 1, let g be the group of squares modulo p (so g is a subgroup of z ∗ p of order q), and let g be a generator of g. the private key is (g, g, q, x) and the public key is (g, g, q, h), where h = g x and x ∈ zq is chosen uniformly. to encrypt a message m ∈ zq, choose a uniform r ∈ zq, compute c1 : = g r mod p and c2 : = h r + m mod p, and let the ciphertext be hc1, c2i. is this scheme cpa-secure? prove your answer.