凜凜 https://i.imgur.com/mLj4PeF.jpg https://i.imgur.com/fIyAnHI.jpg https://i.imgur.com/siRltUq.jpg https://i.imgur.com/2Sx843u.jpg https://i.imgur.com/gNgvfTl.jpg Alice orders a pink car from the car salesmen Bob After seeing the pink car, Alice states that she has never ordered it: How can Bob prove towards a judge that Alice has ordered a pink car? (And that he did not fabricate the order himself) Symmetric cryptography fails because both Alice and Bob can be malicious Can be achieved with public-key cryptography