News.hust.edu.cn On October 26, Nano Letters, an authoritative journal of nanoscience published a research paper online titled Highly Secure Physically Unclonable Cryptographic Primitives Based on Interfacial Magnetic Anisotropy (DOI:10.1021/acs.nanolett.8b03338), which was produced by Professor You Long, professor of the School of Optical and Electronic Information, and his team. Chen Huiming, a 2016 postgraduate student of the School of Optical and Electronic Information, Guo Zhe, a postdoctoral student, and Song Min, a lecturer from Hubei University, are the co-first author of the paper, and Professor You Long is the corresponding author.

In this paper, the relationship between the magnetic anisotropy of Ta/CoFeB/MgO vertical heterojunction film, a commonly used magnetic material, and the thickness of MgO is studied. It is found that a variation of MgO’s thickness at sub-nanometer level may cause a great change in the magnetic performance of the heterojunction, which stems from the competition between the demagnetization field and the anisotropy field of the CoFeB/MgO interface. Due to the inhomogeneity of argon ion etching, the MgO thickness of the abovementioned heterojunction film varies randomly in various places when the film is being etched. This random change cannot be controlled artificially or duplicated, so the variation is considered the magnetic “fingerprint” of the device. The random change can be accurately detected through the anomalous Hall Effect. Random keys extracted from the physical non-clonal function (PUF) component array prepared using the random change are highly secure and stable, and the change can be well applied in the field of information encryption.

What is innovative about this research is that it has solved the problem that the traditional silicon-based PUF can be easily cracked. Due to the delay feature of the transistor, the traditional silicon-based PUF can be easily learned and cracked by machine. The previously proposed PUF component based on conventional magnetic random access memory (MRAM) usually needs a stronger current or an external magnetic field to capture its randomness. The scheme proposed by You Long’s team does not require a stronger current or an external magnetic field, which greatly reduces the integration complexity and power consumption of the component. In addition, the spin PUF is different from the frequently used conventional digital PUF and through a comparison algorithm, the extracted value of stimulated magnetoresistance can produce a much longer key than the traditional binary digital PUF, which greatly improves system security.

The research is funded by the National Natural Science Foundation’s general programsand innovative group programs, as well as by the central universities’ special funds for basic research.