Polymer banknotes are the trend for printed currency and have been adopted by more than fifty countries worldwide. However, over the past years, the quantity of polymer counterfeits has been increasing, so has the quality of counterfeits. This shows that the initial advantage of bringing a new polymer technology to fight against counterfeiting is reducing. To maintain one step ahead of counterfeiters, we propose a novel anti-counterfeiting technique called Polymer Substrate Fingerprinting (PSF). Our technique is built based on the observation that the opacity coating, a critical step during the production of polymer notes, is a stochastic manufacturing process, leaving uneven thickness in the coating layer and the random dispersion of impurities from the ink. The imperfections in the coating layer result in random translucent patterns when a polymer banknote is back-lit by a light source. We show these patterns can be reliably captured by a commodity negative-film scanner and processed into a compact fingerprint to uniquely identify each banknote. Using an extensive dataset of 6,200 sample images collected from 340 UK banknotes, we show that our method can reliably authenticate banknotes, and is robust against rough daily handling of banknotes. Furthermore, we show the extracted fingerprints contain around 900 bits of entropy, which makes it extremely scalable to identify every polymer note circulated globally. As compared with previous or existing anti-counterfeiting mechanisms for banknotes, our method has a distinctive advantage: it ensures that even in the extreme case when counterfeiters have procured the same printing equipment and ink as used by a legitimate government, counterfeiting banknotes remains infeasible because of the difficulty to replicate a stochastic manufacturing process.

中文翻译：

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基于聚合物基材指纹识别的聚合物钞票防伪


聚合物纸币是印刷货币的趋势，已被全球五十多个国家采用。然而，近年来，聚合物假冒产品的数量不断增加，假冒产品的质量也不断提高。这表明引入新的聚合物技术来打击假冒的最初优势正在减弱。为了领先造假者一步，我们提出了一种称为聚合物基底指纹识别（PSF）的新型防伪技术。我们的技术是基于这样的观察而建立的：不透明涂层是聚合物钞票生产过程中的关键步骤，它是一个随机的制造过程，导致涂层厚度不均匀以及墨水中的杂质随机分散。当聚合物钞票受到光源背光照射时，涂层中的缺陷会导致随机的半透明图案。我们证明，这些图案可以通过商品负片扫描仪可靠地捕获，并处理成紧凑的指纹，以唯一地识别每张钞票。使用从 340 张英国纸币收集的 6,200 个样本图像组成的广泛数据集，我们表明我们的方法可以可靠地验证纸币，并且对于纸币的日常粗暴处理具有鲁棒性。此外，我们还发现提取的指纹包含大约 900 位熵，这使得识别全球流通的每张聚合物纸币具有极强的可扩展性。 与以前或现有的纸币防伪机制相比，我们的方法具有独特的优势：即使在造假者采购了与合法政府相同的印刷设备和墨水的极端情况下，伪造纸币仍然是不可能的，因为复制随机制造过程的难度。