One of the most intriguing (yes, it’s a pun) encryption stories (for me) is centuries old and concerns Mary Queen of Scots, from a February 10, 2023 article by Meilan Solly for Smithsonian Magazine, Note: Links have been removed,

Over the course of her 19 years in captivity, Mary, Queen of Scots, wrote thousands of letters to ambassadors, government officials, fellow monarchs and conspirators alike. Most of these missives had the same underlying goal: securing the deposed Scottish queen’s freedom. After losing her throne in 1567, Mary had fled to England, hoping to find refuge at her cousin Elizabeth I’s court. (Mary’s paternal grandmother, Margaret Tudor, was the sister of Elizabeth’s father, Henry VIII.) Instead, the English queen imprisoned Mary, keeping her under house arrest for nearly two decades before ordering her execution in 1587.

Mary’s letters have long fascinated scholars and the public, providing a glimpse into her relentless efforts to secure her release. But the former queen’s correspondence often raises more questions than it answers, in part because Mary took extensive steps to hide her messages from the prying eyes of Elizabeth’s spies. In addition to folding the pages with a technique known as letterlocking, she employed ciphers and codes of varying complexity.

More than 400 years after Mary’s death, a chance discovery by a trio of code breakers is offering new insights into the queen’s final years. As the researchers write in the journal Cryptologia, they originally decided to examine a cache of coded notes housed at the National Library of France as part of a broader push to “locate, digitize, transcribe, decipher and analyze” historic ciphers. Those pages turned out to be 57 of Mary’s encrypted letters, the majority of which were sent to Michel de Castelnau, the French ambassador to England, between 1578 and 1584. All but seven were previously thought to be lost.

Interspersed with a collection of early 16th-century Italian papers, the documents were written in mysterious symbols that offered no clues “as to their sender, recipients or date,” lead author George Lasry, a computer scientist and cryptographer based in Israel, tells Smithsonian magazine. It was only when the scholars spotted the word “Walsingham”—the last name of Elizabeth’s spymaster, Francis Walsingham—that they realized the letters’ significance.

“This was the ‘bingo moment,’” Lasry says. “We were very excited.”

Before getting too excited, the trio set out to confirm whether the letters were already known to historians. While they found copies of a few in British archives, “50 or so are new to historians—and a real gold mine for them,” says Lasry. In total, the letters contain 50,000 words of deciphered material.

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Fascinating, non?

An October 10, 2024 news item on Nanowerk sheds light (more wordplay) on a contemporary approach to encryption,

Seoul National University(SNU) College of Engineering announced that a joint research team led by Professor Ki Tae Nam from the Department of Materials Science and Engineering at SNU and Professor Junil Choi from the Korea Advanced Institute of Science and Technology (KAIST) has developed a novel visible light communication encryption technology with high security using chiral nanoparticles.

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A September 30, 2024 Seoul National University (SNU) press release (also on EurekAlert but published on October 10, 2024), which originated the news item, describes the research in more detail,

Just as a lighthouse provides a guiding beam in the vast darkness of the sea, light-based information transmission has been a crucial means of communication throughout human history. Recently, next-generation communication technology based on visible light, which possesses high frequencies and linearity, has gained attention. It offers advantages such as integration with lighting systems and is free from the electromagnetic interference associated with conventional communication networks. With high security and fast transmission speeds, visible light communication is particularly suitable for local communication systems, especially in military operations involving vehicles, drones, and personnel.

In addition to intensity and wavelength (color), light can carry a vast amount of information through polarization. For instance, 3D movies use polarized filters to deliver two different polarized images to the viewer’s eyes, creating a sense of depth. Recently, efforts have been made to improve the security and performance of visible light communication, including the incorporation of technologies related to polarization, such as quantum information communication based on the superposition of polarization.

The SNU-KAIST joint research team focused on how light polarization can be significantly modulated through interaction with nanomaterials. In this study, they developed an innovative visible light communication encryption technology based on new materials. The core of this technology lies in chiral nanomaterials, which exhibit a symmetric structure when viewed in a mirror but do not overlap. These materials can significantly adjust the tilt of the polarization axis or its rotational properties. Having previously published two papers in 2018 and 2022 in the prestigious journal Nature on “the synthesis and optical device application of chiral nanoparticles with world-class polarization control performance,” the research team has now introduced a visible light communication encryption technology that cannot be replicated or intercepted without detailed information about the nanoparticles.

The chiral nanoparticles used in this technology are created by twisting their crystal structure using biomolecules like proteins and DNA, which possess natural chirality. The optical properties of these nanoparticles cannot be replicated without complete sequence information of the biomolecules used in their synthesis. Therefore, chiral nanoparticles function like fingerprints or unclonable keys in visible light communication, allowing only the receiver with the actual nanoparticles to correctly decode the information. This encryption technology is expected to have significant utility in secure point-to-point communication systems, such as those used in military operations involving drones.

Furthermore, the research team developed a spatiotemporal polarization control device capable of transmitting encrypted polarization information. By combining quantum nanorods, which efficiently emit polarized light, with nanowire materials that provide rotational properties to the light, they used 3D printing to fabricate a polarization control device with hundreds of micrometers of spatial resolution and nanoseconds of temporal resolution, allowing all polarization states to be represented without restriction. The transmitting unit can encrypt and transmit polarization information in a form suited to the polarization control properties of the nanoparticles using this device. This technology is expected to be the foundation for mass production of devices that can control spatiotemporal polarization without being constrained by form factor.

Professor Ki Tae Nam from SNU’s Department of Materials Science and Engineering said, “This research, which actively combines new material technologies with communication technologies, played a crucial role in developing the world’s first and only visible light communication encryption technology. We expect this technology to not only contribute to national defense but also be commercialized rapidly in industrial fields like display technology.” Professor Junil Choi from KAIST’s School of Electrical Engineering added, “This outstanding research result was achieved through joint efforts between material science and electrical engineering experts. In the future, we aim to further develop visible light communication technology based on nanoparticles to create communication systems that are fundamentally impossible to eavesdrop on.” Co-first author Jeong Hyun Han also stated, “We anticipate that this encryption system will act as a platform with great scalability and impact in the field of optical information transmission based on polarization.”

This research was supported by the Future Defense Technology Development Program of the Agency for Defense Development, the Basic Research Laboratory Program of the National Research Foundation of Korea, and private support from LG Display. The research outcome, which has been recognized for its significance, was published in the prestigious multidisciplinary journal Nature Communications on September 27 [2024].

Here’s a link to and a citation for the paper,

Spatiotemporally modulated full-polarized light emission for multiplexed optical encryption by Jiawei Lv, Jeong Hyun Han, Geonho Han, Seongmin An, Seung Ju Kim, Ryeong Myeong Kim, Jung‐El Ryu, Rena Oh, Hyuckjin Choi, In Han Ha, Yoon Ho Lee, Minje Kim, Gyeong-Su Park, Ho Won Jang, Junsang Doh, Junil Choi & Ki Tae Nam. Nature Communications volume 15, Article number: 8257 (2024) DOI: https://doi.org/10.1038/s41467-024-52358-7 Published: 27 September 2024

This paper is open access.