A material distribution apparatus, comprising a material server including a data introduction processor operable to introduce data into material to be distributed with the effect that the introduced data is at least difficult to perceive in the material, and a material impairment processor operable to introduce a reversible impairment into the material. A communications network distributes the impaired material to at least one client processor which includes an impairment reversing processor operable to reverse the impairment of the material to produce client restored material.