4- [10pts] Given is a protocol in which the sender performs the following operation: where M is the message, H is a hash function, E is an encryption algorithm, Il' denotes simple concatenation, and k, k2 are secret keys which are only known to the sender and the receiver. Assume that the sender and the receiver knows concatenation and deconcatenation structure. a. Provide a step-by-step description (e.g., with an itemized list) of what the receiver does upon reception of y b. For the following questions, the statement is either correct or wrong. Circle yes or no. Justify your answer i. An attacker can alter the Message M, (YES ANO) ii. Given protocol does not provide authentication. (YES/ ii. Signature cannot be repudiated. (YES)/ NO) Lo 4- [10pts] Given is a protocol in which the sender performs the following operation: where M is the message, H is a hash function, E is an encryption algorithm, Il' denotes simple concatenation, and k, k2 are secret keys which are only known to the sender and the receiver. Assume that the sender and the receiver knows concatenation and deconcatenation structure. a. Provide a step-by-step description (e.g., with an itemized list) of what the receiver does upon reception of y b. For the following questions, the statement is either correct or wrong. Circle yes or no. Justify your answer i. An attacker can alter the Message M, (YES ANO) ii. Given protocol does not provide authentication. (YES/ ii. Signature cannot be repudiated. (YES)/ NO) Lo