An important aspect of security and defense is information gathering, dissemination, processing,and analysis. Central to this is the encryption and decryption of messages for storage and transmission. Although public-key cryptosystems are the state of the art currently, there is a place for private-key systems in cases where hardware implementation permits very high through puts. Optical implementation is a candidate for this. Optics has some very promising scalability advantages over purely electronic systems as, in principle, the size of the key can be increased without increasing the encryption or decryption time..
