Stream ciphers and PRGs: We saw that one can build a secure stream cipher directly from a PRG. After learning about weaknesses found in RC4, Alice wants to encrypt a message for Bob using a stream cipher built from two candidate PRGs, call them G, and G,. The goal is that if either is a secure PRG, the resulting cipher is a secure stream cipher. Which of the following options will provide semantically secure encryption? If so, explain why. If not, explain a distinguishing attack a. Encrypt(m, k) = m G1(k) V G2 (k) b. Encrypt(m, k)-me G,(k)G (k) c. Encrypt(m, k)-[m Gi(k)] ll [m G2 (k)] (where V is a bitwise OR) (whereis a bitwise exclusive-OR) ( where is a concatenation )