Encryption On Surfaces: Meet DASAs

Encryption On Surfaces: Meet DASAs

We are faced with an ever-increasing number of fake goods and spoof devices. So how can we best identify that an object is what it is meant to be? Along with this, if we can identify something uniquely, we could track it journey and pick up key information that could be used for its life cycle understanding. This research is often defined as supporting a PUF — Physically Unclonable Function.

Now a research team at the Chinese Academy of Sciences has come up with a way of creating stimuli-responsive materials for data encryption and anti-counterfeiting. This relates to work related to the study of smart photochromic and luminescent tissues related to the camouflage and cloaking methods found in nature [here][1]:

In the research, they used multi-responsive donor-acceptor Stenhouse adducts (DASAs). DASAs were discovered in 2014 and are photoswitchable compounds that have donors, acceptors, and bridges. These are tuned with light between 450 and 750 nm, but, in previous work, researchers have generally struggled to control their operation.

The paper outlines how previous work on combination logic using DASAs [A, B in Figure 2] has been expanded to drive a state drive system [C in Figure 2], using acceptors and donors [D in Figure 2]. The usage of a state-driven system is required for encryption systems, and where the application of a specific encryption key can drive the encryption method through a number of states in order to produce a defined output. The reverse often involves reversing these states back to the original data — and using the same encryption key. This is known as symmetric key encryption.

Overall the work allows for both a unique encryption key to be entered — the stimuli — and for the DASAs to go through the correct sequence of encryption operations. The selected DASAs including DASA-4, DASA-5, and DASA-7 to DASA-9, and 8 have been constructed to make a figure “8” (A and B in Figure 3). These can be designed so that they can be created with distinct colours and have differing photochromatic behaviours. When an incorrect sequence is applied, it will generate meaningless output data. We can see different routes through the encryption with C in Figure 3.

But what about the production of the DASAs? Well, the authors propose that the materials can be made into a gel and with shape morphing, we can recover the output data. This could be revealed on a finger, plastic bottle or even on glass (Figure 4).

Conclusion

I love being involved in research, as there’s always something that comes along that changes your viewpoint on this and provides new opportunities for advancement. While I don’t understand the chemistry around DASAs, I do understand how encryption could be applied to this field. The strive for PUFs, continues, and if we can link actual devices to cryptographic entities, we will be getting close to creating an Internet of Trusted Things. The next thing will be in how we make the best use of this trusted infrastructure.

If you are interested in how PUFs work and could be linked to devices, try here:

References

[1] Dong, Y., Ling, Y., Wang, D., Liu, Y., Chen, X., Zheng, S., … & Huang, W. (2022). Harnessing molecular isomerization in polymer gels for sequential logic encryption and anticounterfeiting. Science Advances, 8(44), eadd1980.