{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,17]],"date-time":"2025-10-17T14:18:41Z","timestamp":1760710721861,"version":"3.41.0"},"reference-count":27,"publisher":"Association for Computing Machinery (ACM)","issue":"1","license":[{"start":{"date-parts":[[2021,9,29]],"date-time":"2021-09-29T00:00:00Z","timestamp":1632873600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/www.acm.org\/publications\/policies\/copyright_policy#Background"}],"funder":[{"name":"NSF","award":["CRII-1849739"],"award-info":[{"award-number":["CRII-1849739"]}]}],"content-domain":{"domain":["dl.acm.org"],"crossmark-restriction":true},"short-container-title":["J. Emerg. Technol. Comput. Syst."],"published-print":{"date-parts":[[2022,1,31]]},"abstract":"<jats:p>\n            <jats:bold>Electronic cash<\/jats:bold>\n            (\n            <jats:bold>e-Cash<\/jats:bold>\n            ) is a digital alternative to physical currency such as coins and bank notes. Suitably constructed, e-Cash has the ability to offer an anonymous offline experience much akin to cash, and in direct contrast to traditional forms of payment such as credit and debit cards. Implementing security and privacy within e-Cash, i.e., preserving user anonymity while preventing counterfeiting, fraud, and double spending, is a non-trivial challenge. In this article, we propose major improvements to an e-Cash protocol, termed PUF-Cash, based on\n            <jats:bold>physical unclonable functions<\/jats:bold>\n            (\n            <jats:bold>PUFs<\/jats:bold>\n            ). PUF-Cash was created as an offline-first, secure e-Cash scheme that preserved user anonymity in payments. In addition, PUF-Cash supports remote payments; an improvement over traditional currency. In this work, a novel multi-trusted-third-party exchange scheme is introduced, which is responsible for \u201cblinding\u201d Alice\u2019s e-Cash tokens; a feature at the heart of preserving her anonymity. The exchange operations are governed by machine learning techniques which are uniquely applied to optimize user privacy, while remaining resistant to identity-revealing attacks by adversaries and trusted authorities. Federation of the single trusted third party into multiple entities distributes the workload, thereby improving performance and resiliency within the e-Cash system architecture. Experimental results indicate that improvements to PUF-Cash enhance user privacy and scalability.\n          <\/jats:p>","DOI":"10.1145\/3441139","type":"journal-article","created":{"date-parts":[[2021,9,29]],"date-time":"2021-09-29T19:16:42Z","timestamp":1632943002000},"page":"1-26","update-policy":"https:\/\/doi.org\/10.1145\/crossmark-policy","source":"Crossref","is-referenced-by-count":2,"title":["Enhancing Privacy in PUF-Cash through Multiple Trusted Third Parties and Reinforcement Learning"],"prefix":"10.1145","volume":"18","author":[{"given":"Georgios","family":"Fragkos","sequence":"first","affiliation":[{"name":"University of New Mexico, New Mexico, United States"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Cyrus","family":"Minwalla","sequence":"additional","affiliation":[{"name":"Bank of Canada, Ottawa, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Eirini Eleni","family":"Tsiropoulou","sequence":"additional","affiliation":[{"name":"University of New Mexico, New Mexico, United States"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jim","family":"Plusquellic","sequence":"additional","affiliation":[{"name":"University of New Mexico, New Mexico, United States"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"320","published-online":{"date-parts":[[2021,9,29]]},"reference":[{"key":"e_1_2_1_1_1","doi-asserted-by":"publisher","DOI":"10.1109\/MDT.2013.2247459"},{"key":"e_1_2_1_2_1","doi-asserted-by":"publisher","DOI":"10.1109\/CCC.2009.42"},{"key":"e_1_2_1_3_1","doi-asserted-by":"publisher","DOI":"10.1145\/2213977.2213983"},{"key":"e_1_2_1_4_1","first-page":"99","article-title":"On a measure of divergence between two statistical populations defined by their probability distributions","volume":"35","author":"Bhattacharyya A.","year":"1943","unstructured":"A. Bhattacharyya . 1943 . On a measure of divergence between two statistical populations defined by their probability distributions . Bulletin of the Calcutta Mathematical Society 35 (1943), 99 \u2013 109 . A. Bhattacharyya. 1943. On a measure of divergence between two statistical populations defined by their probability distributions. Bulletin of the Calcutta Mathematical Society 35 (1943), 99\u2013109.","journal-title":"Bulletin of the Calcutta Mathematical Society"},{"key":"e_1_2_1_5_1","doi-asserted-by":"publisher","DOI":"10.5555\/188105.188172"},{"key":"e_1_2_1_6_1","volume-title":"Physical unclonable function (PUF)-based e-cash transaction protocol (PUF-Cash). Cryptography 3","author":"Calhoun Jeff","year":"2019","unstructured":"Jeff Calhoun , Cyrus Minwalla , Charles Helmich , Fareena Saqib , Wenjie Che , and Jim Plusquellic . 2019. Physical unclonable function (PUF)-based e-cash transaction protocol (PUF-Cash). Cryptography 3 ( 2019 ), Article 3, 21\u00a0pages. Jeff Calhoun, Cyrus Minwalla, Charles Helmich, Fareena Saqib, Wenjie Che, and Jim Plusquellic. 2019. Physical unclonable function (PUF)-based e-cash transaction protocol (PUF-Cash). Cryptography 3 (2019), Article 3, 21\u00a0pages."},{"key":"e_1_2_1_7_1","doi-asserted-by":"publisher","DOI":"10.1007\/11426639_18"},{"key":"e_1_2_1_8_1","doi-asserted-by":"publisher","DOI":"10.1109\/SP.2007.15"},{"volume-title":"Advances in Cryptology","author":"Chaum David","key":"e_1_2_1_9_1","unstructured":"David Chaum . 1983. Blind signatures for untraceable payments . In Advances in Cryptology . Springer US , Boston, MA , 199\u2013203. David Chaum. 1983. Blind signatures for untraceable payments. In Advances in Cryptology. Springer US, Boston, MA, 199\u2013203."},{"key":"e_1_2_1_10_1","doi-asserted-by":"publisher","DOI":"10.5555\/646753.704915"},{"key":"e_1_2_1_11_1","volume-title":"Analysis of entropy in a hardware-embedded delay PUF. Cryptography 1, 1","author":"Che Wenjie","year":"2017","unstructured":"Wenjie Che , Venkata\u00a0 K. Kajuluri , Mitchell Martin , Fareena Saqib , and Jim Plusquellic . 2017. Analysis of entropy in a hardware-embedded delay PUF. Cryptography 1, 1 ( 2017 ). DOI:https:\/\/doi.org\/10.3390\/cryptography1010008 10.3390\/cryptography1010008 Wenjie Che, Venkata\u00a0K. Kajuluri, Mitchell Martin, Fareena Saqib, and Jim Plusquellic. 2017. Analysis of entropy in a hardware-embedded delay PUF. Cryptography 1, 1 (2017). DOI:https:\/\/doi.org\/10.3390\/cryptography1010008"},{"key":"e_1_2_1_12_1","volume-title":"Leveraging distributions in physical unclonable functions. Cryptography 1, 3","author":"Che Wenjie","year":"2017","unstructured":"Wenjie Che , Venkata\u00a0 K. Kajuluri , Fareena Saqib , and Jim Plusquellic . 2017. Leveraging distributions in physical unclonable functions. Cryptography 1, 3 ( 2017 ). Wenjie Che, Venkata\u00a0K. Kajuluri, Fareena Saqib, and Jim Plusquellic. 2017. Leveraging distributions in physical unclonable functions. Cryptography 1, 3 (2017)."},{"key":"e_1_2_1_13_1","volume-title":"A privacy-preserving, mutual PUF-based authentication protocol. Cryptography 1, 1","author":"Che Wenjie","year":"2016","unstructured":"Wenjie Che , Mitchell Martin , Goutham Pocklassery , Venkata\u00a0 K. Kajuluri , Fareena Saqib , and Jim Plusquellic . 2016. A privacy-preserving, mutual PUF-based authentication protocol. Cryptography 1, 1 ( 2016 ), Article 3, 17\u00a0pages. DOI:https:\/\/doi.org\/10.3390\/cryptography1010003 10.3390\/cryptography1010003 Wenjie Che, Mitchell Martin, Goutham Pocklassery, Venkata\u00a0K. Kajuluri, Fareena Saqib, and Jim Plusquellic. 2016. A privacy-preserving, mutual PUF-based authentication protocol. Cryptography 1, 1 (2016), Article 3, 17\u00a0pages. DOI:https:\/\/doi.org\/10.3390\/cryptography1010003"},{"volume-title":"Proc. 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