Methods and devices for optimizing rendering of an encrypted 3D graphical object

The graphical characteristics of 3D graphical objects encrypted using format-preserving encryption makes rendering of such objects quite inefficient by non-authorized devices. To optimize the rendering of a three-dimensional graphical object represented by a list of points and a list of surfaces defined by points in the list of points, a device receives the graphical object; encrypts the graphical object using a format-preserving encryption method to obtain an encrypted graphical object; encapsulates the encrypted graphical object to obtain an encapsulated graphical object by adding at least one encapsulation by adding for each encapsulation, to the list of surfaces, a plurality of surfaces that together enclose the encrypted graphical object and, in an embodiment, at least one point to the list of points; and outputs the encapsulated graphical object. Decryption is performed by essentially reversing the encryption.