The authors introduce EyeDecrypt, a novel technology for privacy-preserving human-computer interaction. EyeDecrypt allows only authorized users to decipher data shown on a public display, such as an electronic screen or printed material; in the former case, the authorized user can then interact with the system (e.g., by pressing buttons), without revealing the details of the interaction to others who may be watching. The user views data on a closely-held personal device, such as a pair of smart glasses with a camera and heads-up display, or a Smartphone. The decrypted data is displayed as an image overlay on the personal device - a form of augmented reality. The user's inputs are protected through randomization.