A nonlinear ring interferometer (NRI) is chosen as a generalized structure model of encryption devices in nonlinear-dynamic cryptology. The suggested concept of chains of transposition points (CTP) allows NRI to be represented as a system, in which optical-physical interactions have the graph structure. For analysis and synthesis of similar systems, route-operator formalism is being proposed. Processes in the NRI are described and the model of a decoder exploiting a chaotic response is synthesized using this formalism. The possible foundations for classification of devices in nonlinear dynamic cryptography and different versions of such devices are given. Some examples of computer simulation of encryption/decryption in the static mode and the mode of dynamic chaos are presented and the effect of model parameters on the degree of communication confidentiality is illustrated. The concept of determined spatial chaos arising in the static mode of a dynamic system is discussed. A relation is found between the CTP and discrete maps.