1. A method for privacy-retaining face identification comprising: dividing at least one input face into a first set of patches; providing an assortment of patch profiles for each patch in said first set of patches, each patch profile in said assortment being associated with a unique index thereby to define an assortment of unique indices; for each individual patch in the input face, finding at least one patch profile within said assortment of patch profiles which most resembles said individual patch, thereby to define a first set of indices from among said assortment of unique indices whose corresponding patch profiles most resemble said input face's patches respectively; and using a privacy preserving computation to generate a physical output indicative of a comparison of said input face and at least one target face by comparing first and second functions of said first set of indices and of a second set of indices respectively, said second set of indices corresponding to patch profiles which most resemble a second set of patches into which said target face has been divided.