The next-generation communication network driven by optical technology will be achieved in the sixth-generation mobile communication system (6G) of the Innovative Optical and Wireless Network (IOWN) era promoted by NTT.However, a problem of concern here is cryptographic technology.For example, even if optical circuits can be achieved, cryptographic operations in their present form would generate delays or excessive power consumption preventing the advantages of optical technology from being fully used.To solve this problem, NTT is researching technology for replacing the complex processing of cryptographic operations traditionally performed by electronic circuits with optical cryptographic operations.In this article, we talk with NTT Distinguished Researcher Junko Takahashi who devised an "optical-operations technique" supporting the IOWN era and implemented "optical cryptographic circuits."We hear about the present state of research in optical cryptographic technology and the future outlook for this research.