The University of SydneyPage 49Public-key certification–motivation: Trudy plays pizza prank on Bob–Trudy creates e-mail order: Dear Pizza Store, Please deliver to me four pepperoni pizzas. Thank you, Bob–Trudy signs order with her private key–Trudy sends order to Pizza Store–Trudy sends to Pizza Store her public key, but says it’s Bob’s public key–Pizza Store verifies signature; then delivers four pepperoni pizzas to Bob–Bob doesn’t even like pepperoni–What allowed this prank a successful one?