Chip & PIN only solves part of the problem: authenticating that you are you. You could still be a deadbeat. There are three parties involved: the merchant, you

Chip & PIN only solves part of the problem: authenticating that you are you. You could still be a deadbeat. There are three parties involved: the merchant, you, and the bank. You are ordering the bank to transfer funds to the merchant. Naturally, the bank has a say in the matter. After all, you might or not be able to afford the shiny Maybach. To keep out hackers, the whole interaction needs to be strongly encrypted. That requires the merchant, you, and the bank to be able to communicate securely. Mag stripes are not secure. But your phone, provided you are not a complete ditz, offers hope. Merchant presents bill to your phone. You approve (or not — maybe you stole the phone and don't know the code). Merchant presents your approval to the bank. The bank approves or declines, and the transaction completes or it doesn't. Eavesdroppers can intercept the encrpted interactions but can't replay them with any effect other than to raise alarms. Why isn't something like the above already in place? Because it will cost a bundle to convert, and current credit card fraud rates are at the single-digit basis point level. Actually, the reason improvements like chip and pin are not prevalent in the US is that the US has historically had better datacomm than other places, so the need to authenticate offline was less urgent. At least, that's the excuse I've heard.