Abstract: A secure system using a continuously-changing key that depends on the user's body part. A preferred embodiment obtains an image of the user's fingerprint and cements it according to a random generator. Only part of the image and not all of the image is sent at one time. The random segmentation insures that part of the image that is sent continuously varies from time to time. Therefore, an unauthorized receiver can receive only part but not all of the image. That only part of the image which is received will usually not be the same at the second as it is at the first time. Therefore, a received code cannot later be used to fool the system with the same credit card.