Encryption of an image is achieved through application of a homomorphic encryption function to produce cipher images for each image. Encryption is performed individually on subvalues of a pixels intensity value, wherein the pixels intensity value can be described as a sum of the smaller numerical sub-values. The encrypted values for each sub-value form encrypted images that can be transferred or stored on insecure media. Separate encryption approaches can be applied to individual sets of the numerical sub-values to improve security.