A magnetic interface card appears to be a payment card conventionally provided with an electromagnetic stripe and magnetic data tracks. A magnetic emissive element is disposed in the magnetic interface card body under the magnetic data tracks that can emit a variety of ISO-7813 track-2 data strings. A photo-sensor is included to receive a series of optically encoded flashes from a personal trusted device (PTD) smartphone screen that securely communicate one-time-use account information and operational parameters from a financial transaction server. The large installed base of legacy point-of-sale magnetic card readers can continue to be used without any hardware or software modifications, and card security is improved by the change to one-time-use access numbers.