Consider the following public-key encryption scheme. The public key is (p,g, h) and the private key is x, generated exactly as in the El Gamal encryption scheme. In order to encrypt a bit b, the sender does the following: If b = 0, then choose Y ER Zp-1 and compute cu = g and c2 = h'. The ciphertext is (C1, C2) If b = 1, then choose y, z ER Zp-1, compute ci gy and c2 = g , and set the ciphertext equal to (C1, C2). Show that it is possible to decrypt efficiently given knowledge of x. Prove that this encryption scheme is CPA-secure if the decisional Diffie- Hellman problem is hard. Consider the following public-key encryption scheme. The public key is (p,g, h) and the private key is x, generated exactly as in the El Gamal encryption scheme. In order to encrypt a bit b, the sender does the following: If b = 0, then choose Y ER Zp-1 and compute cu = g and c2 = h'. The ciphertext is (C1, C2) If b = 1, then choose y, z ER Zp-1, compute ci gy and c2 = g , and set the ciphertext equal to (C1, C2). Show that it is possible to decrypt efficiently given knowledge of x. Prove that this encryption scheme is CPA-secure if the decisional Diffie- Hellman problem is hard