5. a. PI O OI FIGURE Q5a describes dual signature in a Secure Online Transaction (SET) H H Payment Information PIMD OIMD WWW PI OI = Order Information H = Hash function (SHA-1) || = Concatenation || H POMD PIMD= PI message digest OIMD Ol message digest POMD = Payment Order message digest = Encryption (RSA) E KR = Customer's private signature key FIGURE Q5a KR E Dual Signature *********** a. Explain the above process using simple mathematical notations. [4 marks] b. With reference to the above diagram, assess the importance of dual signature in an online transaction involving a purchase of goods or services using a credit card. [6 marks]