Abstract: Image data representative of features of a respective plurality images are transformed using a two dimension discrete cosine transform (DCT), and the DCT sign coefficients of the respective DCT transforms for the images are selectively used to generate a highly compressed and secure one-dimension binary data representation of a subject image whose image data has undergone a DCT transform. The binary data representation can be, for example, of a face image and is readily applicable to a passport, a credit card, a driver's license, an ID card, and the like, for use in rapid, secure face authentication.