New light-based encryption technology

Researchers at the Darmstadt University of Technology have created an encryption system based on the polarization of light. The data is encoded directly in the angle of polarization, a technique impossible to decipher without a reference light ray.

Cryptographic techniques must constantly evolve in order not to be made obsolete by technological advances. Researchers at Darmstadt University of Technology have successfully created a new encryption method using the properties of unpolarized light. The technique is called Ghost Polarization Communication (GPC) or phantom polarization communication.

Light is composed of a magnetic field and an electric field. With polarized light, like lasers, the orientation of the electric field is fixed. Conversely, for non-polarized light, the magnetic field fluctuates randomly. The researchers were therefore interested in using these fluctuations as a generator of random numbers.

The message is hidden in the polarization of light
The data communicated is encoded in a light ray, using a delay blade to change the angle of polarization. The recipient receives at the same time a second unmodified reference light ray. The message is then deciphered by comparing the polarization angles of the two rays. Without this reference, it is not possible to decipher the message.

The researchers said the current test was a first demonstration of feasibility. For now, the transmission speed is too slow for practical use. However, the team used components already commercially available (sources and optical fibers). Once their method is more refined, they hope that it can be directly connected to existing systems.

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