Cryptography at the Speed of Light

As the world moves toward All-Photonics Networks, we are reimagining encryption using optical technology – with the goal of delivering high security at the speed of light. 

This represents a huge shift. Right now, computing devices mainly use electronics to process and transmit information – and for encryption and security. But now photonics-based networks – part of the Innovative Optical & Wireless Network (IOWN) technologies – are already in production, using light instead of electrons and improving energy efficiency, speed, and latency. Traditional encryption, based on electronic circuits, is not compatible with photonics. And, even if encryption could be done via optical circuits, cryptographic operations in their present form would cause delays or excessive power consumption – mitigating the advantages of photonics.  

There’s an innovative new solution in development: optical cryptography. 

The Optical Cryptography Challenge 

The idea of optical cryptography was long thought to be impossible. Cryptography involves performing complex mathematical and logical operations on digital data, often in binary form. These operations, crucial for securing communications, have always been carried out electronically. But optics are inherently analog, and analog processes are not naturally suited to digital computations. 

The analog nature of light requires rethinking how cryptographic functions are designed. Unlike digital systems, which can easily represent binary data, optical systems must use the properties of light to perform logical operations. This is not just about substituting electrical signals with optical signals but creating entirely new algorithms. 

This presented a substantial roadblock for NTT Distinguished Researcher Junko Takahashi, who began investigating whether optical cryptographic circuits could be built. 

Pioneering Optical Cryptographic Circuits 

Initially, Takahashi and her team faced skepticism. Cryptographic operations have always been executed using electronic components, so the idea of moving this to optics seemed like an insurmountable hurdle. Even worse, the optical operations devices necessary for cryptography were still under development and not yet ready for practical use. Despite these challenges, the team made a remarkable breakthrough. 

After numerous experiments and tests, in 2022 Takahashi and her team were able to perform a cryptographic function using an optical circuit for the first time. They used an infrared camera to capture images of the optical circuit moving, and in doing so they became the first in the world to conduct a cryptographic function using an optical circuit. 

This was a major leap forward, but it is only the beginning. The optical circuit Takahashi and her team developed still used some electrical components, and the ultimate goal is to create a fully optical cryptographic system that would use light for both processing and communication. 

The Path Toward a Fully Optical Cryptography System 

The research on optical computing elements is still in its infancy, and further applied research relies on development in this area. Fundamental optical computing elements such as memory storage and registers use electrical systems so, for now, researchers are still combining optical circuits with electronic components to achieve operational cryptographic systems. 

Takahashi’s team is now working toward a “photonic disaggregated computing platform” that would be capable of running high-speed cryptographic functions using minimal power, an advancement that could impact the information and communication field. By 2030, their goal is to achieve optical cryptographic systems that will be both faster and more energy-efficient than current digital encryption methods. 

The Future of Optical Cryptography in Space and Beyond 

This work may eventually go beyond cryptography applications here on Earth. Far off in the future, as optical circuits evolve, they could be installed in satellites to operate cryptographic circuits in space. This vision aligns with the broader goals of IOWN, which aims to support not just Earth-based networks but space-based computing environments as well.  

Optical cryptography research is laying the groundwork for a future where encryption is faster, more efficient, and more secure than ever before. As the world moves toward IOWN and beyond, optical cryptography could become the standard for securing communications. 

• Cyber Security