1. A method of authenticating, the method comprising: generating, by a second entity, a first repaired image by applying repair parameters, representing one or more repair operations, to a first marked image; sending the repair parameters to a first entity from the second entity; receiving, at the second entity from the first entity, a second repaired image, the second repaired image generated based on the repair parameters sent by the second entity; and authenticating the first entity when the second repaired image, received from the first entity, matches the first repaired image, the second repaired image, received from the first entity, matching the first repaired image when the second repaired image is generated by the first entity using the first marked image and the repair parameters sent by the second entity.