A camera with a built in microprocessor system programmed to receive an input password and indicium from a host computer. The camera is configured to use the indicium in combination with a conversion formula to mark an original acquired image in a non-destructive manner to form modified image data and add the indicium to an image header. The camera also creates image authentication data for comparison with corresponding data of a questionable second image to determine if the second image is the same as or different from the original image. This process of marking and creating authentication data all occur during acquisition and prior to any image data storage in a medium from which a person could subsequently access data. The camera takes the authentication data and stores it along with the marked image data in memory for subsequent transmission to the host computer. The preferred embodiment of the authentication involves the creation of checksum data, involving the addition of pixel values from each image row and each image column. These sums are then stored in a lookup table for future use in comparing with the result of the same checksum calculation done on questionable image data at a future time. The original image can be viewed only through presentation of the password.