At the time Ash Wednesday was written there was no practical application of optical refraction as a means of secure encryption that the author is aware of. So it remains today, although there has certainly been research on the subject, notably in a paper published in the scientific journal Nature Communications, April 7, 2023. That paper can be accessed here.
The fictional CIPHER key (Commercial & Industrial Phased Energy Refraction) is imagined as a molded crystal-like structure (like quartz crystals, pictured) but with a randomized internal density matrix (so not a true crystal). After manufacture, the refracted laser pulse’s properties would be empirically matched to a receiver responding to that precise output alone which, when coupled with the key, would form a secure mechanism. Since the proposed density matrix would be infinitely variable (instead of a finite combination of 0s and 1s), the coming of quantum computing would not be the threat to encryption by light refraction that it is to existing digital encryption.
In the CIPHER key, the only things being ‘encrypted’ are the laser pulse’s properties post-refraction—it is just a lock. Zhang et al.’s Nature Communications paper proposes to encrypt data, something much more ambitious and applicable broadly in computer network and telecommunications traffic. But the underlying principle is, like the CIPHER key, an “…optical security strategy…which fully exploits the abundant degrees of freedom of light as well as the spatial dislocation as key parameters“
Given the overarching theme of Ash Wednesday, it is interesting to note that all the authors of this paper are members of research institutions operating under the aegis of the Chinese Academy of Sciences.
ASH WEDNESDAY