4. (30 points) In class, we'd seen the stateful variant of CBC mode is IND-CPA insecure. However, the stateful variants of OFB and CTR modes are IND-CPA secure. Write the IND-CPA attack games for the stateful OFB and CTR modes, akin to the one for stateful CBC mode, assuming adversary knows the first IVonce. Briefly point out and explain why the attack games fail. 4. (30 points) In class, we'd seen the stateful variant of CBC mode is IND-CPA insecure. However, the stateful variants of OFB and CTR modes are IND-CPA secure. Write the IND-CPA attack games for the stateful OFB and CTR modes, akin to the one for stateful CBC mode, assuming adversary knows the first IVonce. Briefly point out and explain why the attack games fail