Many merchants and retail workers are watching their lives play in slow motion when they process credit cards. To combat fraudulent transactions, the retail industry is shifting away from the traditional magnetic stripe toward tiny computer chips embedded inside cards. The chip technology, known as E.M.V. (for Europay, MasterCard and Visa), has been around for decades in Europe. But starting last October in the United States, banks pushed the liability of purchases made with counterfeit credit cards onto merchants.