{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,11]],"date-time":"2026-04-11T01:39:06Z","timestamp":1775871546136,"version":"3.50.1"},"reference-count":24,"publisher":"Association for Computing Machinery (ACM)","issue":"3","license":[{"start":{"date-parts":[[2019,7,31]],"date-time":"2019-07-31T00:00:00Z","timestamp":1564531200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/www.acm.org\/publications\/policies\/copyright_policy#Background"}],"funder":[{"name":"Singapore MOE","award":["SUTDT12017004"],"award-info":[{"award-number":["SUTDT12017004"]}]},{"DOI":"10.13039\/501100001321","name":"National Research Foundation","doi-asserted-by":"crossref","award":["NRF2014EWT-EIRP002-026"],"award-info":[{"award-number":["NRF2014EWT-EIRP002-026"]}],"id":[{"id":"10.13039\/501100001321","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["61429301 and 61833015"],"award-info":[{"award-number":["61429301 and 61833015"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"name":"SUTD-ZJU IDEA","award":["201805"],"award-info":[{"award-number":["201805"]}]},{"DOI":"10.13039\/501100001475","name":"Nanyang Technological University","doi-asserted-by":"crossref","award":["Start-up Grant"],"award-info":[{"award-number":["Start-up Grant"]}],"id":[{"id":"10.13039\/501100001475","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":["dl.acm.org"],"crossmark-restriction":true},"short-container-title":["ACM Trans. Cyber-Phys. Syst."],"published-print":{"date-parts":[[2019,7,31]]},"abstract":"<jats:p>Many clock synchronization protocols based on message passing, e.g., the Network Time Protocol (NTP), assume symmetric network delays to estimate the one-way packet transmission time as half of the round-trip time. As a result, asymmetric network delays caused by either network congestion or malicious packet delays can cause significant synchronization errors. This article exploits sinusoidal voltage signals of an alternating current (AC) power grid to limit the impact of the asymmetric network delays on these clock synchronization protocols. Our extensive measurements show that the voltage signals at geographically distributed locations in a city are highly synchronized. Leveraging calibrated voltage phases, we develop a new clock synchronization protocol that we call Grid Time Protocol (GTP), which allows direct measurement of one-way packet transmission times between its slave and master nodes, subject to an analytic condition that can be easily verified in practice. The direct measurements render GTP resilient against asymmetric network delays under this condition. A prototype implementation of GTP maintains sub-millisecond synchronization accuracy for two nodes tens of kilometers apart in the presence of malicious packet delays. The result has been demonstrated for both Singapore and Hangzhou, China. Simulations driven by real network delay measurements between Singapore and Hangzhou under both normal and congested network conditions also show the synchronization accuracy improvement by GTP. We believe that GTP is suitable for grid-connected distributed systems that are currently served by NTP but desire higher resilience against unfavorable network dynamics and packet delay attacks.<\/jats:p>","DOI":"10.1145\/3342048","type":"journal-article","created":{"date-parts":[[2019,8,9]],"date-time":"2019-08-09T12:22:28Z","timestamp":1565353348000},"page":"1-26","update-policy":"https:\/\/doi.org\/10.1145\/crossmark-policy","source":"Crossref","is-referenced-by-count":3,"title":["Resilient Clock Synchronization Using Power Grid Voltage"],"prefix":"10.1145","volume":"3","author":[{"given":"Dima","family":"Rabadi","sequence":"first","affiliation":[{"name":"Institute for Infocomm Research (I2R), A*STAR, Connexis South Tower, Singapore"}]},{"given":"Rui","family":"Tan","sequence":"additional","affiliation":[{"name":"Nanyang Technological University, Nanyang Avenue, Singapore"}]},{"given":"David K. Y.","family":"Yau","sequence":"additional","affiliation":[{"name":"Singapore University of Technology and Design, Singapore"}]},{"given":"Sreejaya","family":"Viswanathan","sequence":"additional","affiliation":[{"name":"Advanced Digital Sciences Centre, Singapore"}]},{"given":"Hao","family":"Zheng","sequence":"additional","affiliation":[{"name":"Zhejiang University, Hangzhou, P.R. China"}]},{"given":"Peng","family":"Cheng","sequence":"additional","affiliation":[{"name":"Zhejiang University, Hangzhou, P.R. China"}]}],"member":"320","published-online":{"date-parts":[[2019,8,9]]},"reference":[{"key":"e_1_2_1_1_1","unstructured":"2019. NTP Security Analysis. Retrieved from: https:\/\/www.eecis.udel.edu\/&sim;mills\/security.html.  2019. NTP Security Analysis. Retrieved from: https:\/\/www.eecis.udel.edu\/&sim;mills\/security.html."},{"key":"e_1_2_1_2_1","volume-title":"Networking and Online Games: Understanding 8 Engineering Multiplayer Internet Games","author":"Armitage Grenville","unstructured":"Grenville Armitage , Mark Claypool , and Philip Branch . 2006. Networking and Online Games: Understanding 8 Engineering Multiplayer Internet Games . Wiley . Grenville Armitage, Mark Claypool, and Philip Branch. 2006. Networking and Online Games: Understanding 8 Engineering Multiplayer Internet Games. Wiley."},{"key":"e_1_2_1_4_1","doi-asserted-by":"publisher","DOI":"10.1145\/844128.844143"},{"key":"e_1_2_1_5_1","doi-asserted-by":"publisher","DOI":"10.1145\/958491.958508"},{"key":"e_1_2_1_6_1","doi-asserted-by":"publisher","DOI":"10.1109\/TMC.2013.43"},{"key":"e_1_2_1_7_1","volume-title":"Network Security: Know It All: Know It All. Morgan Kaufmann.","author":"Joshi James","year":"2008","unstructured":"James Joshi . 2008 . Network Security: Know It All: Know It All. Morgan Kaufmann. James Joshi. 2008. Network Security: Know It All: Know It All. Morgan Kaufmann."},{"key":"e_1_2_1_8_1","doi-asserted-by":"publisher","DOI":"10.1109\/TC.1987.5009516"},{"key":"e_1_2_1_9_1","volume-title":"Power System Stability and Control","author":"Kundur Prabha","unstructured":"Prabha Kundur . 1994. Power System Stability and Control . McGraw-Hill . Prabha Kundur. 1994. Power System Stability and Control. McGraw-Hill."},{"key":"e_1_2_1_10_1","doi-asserted-by":"publisher","DOI":"10.1109\/TSG.2010.2053392"},{"key":"e_1_2_1_11_1","volume-title":"Proceedings of the Conference on IEEE 1588","author":"Lee Kang B.","unstructured":"Kang B. Lee and J. Eldson . 2004. Standard for a precision clock synchronization protocol for networked measurement and control systems . In Proceedings of the Conference on IEEE 1588 , Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems. Kang B. Lee and J. Eldson. 2004. Standard for a precision clock synchronization protocol for networked measurement and control systems. In Proceedings of the Conference on IEEE 1588, Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems."},{"key":"e_1_2_1_12_1","doi-asserted-by":"publisher","DOI":"10.1145\/1999995.2000012"},{"key":"e_1_2_1_13_1","doi-asserted-by":"publisher","DOI":"10.1145\/3199676"},{"key":"e_1_2_1_14_1","doi-asserted-by":"publisher","DOI":"10.1145\/2348543.2348584"},{"key":"e_1_2_1_15_1","doi-asserted-by":"publisher","DOI":"10.1109\/TSG.2011.2116162"},{"key":"e_1_2_1_16_1","doi-asserted-by":"publisher","DOI":"10.1145\/1031495.1031501"},{"key":"e_1_2_1_17_1","doi-asserted-by":"publisher","DOI":"10.1109\/ISPCS.2012.6336612"},{"key":"e_1_2_1_18_1","doi-asserted-by":"publisher","DOI":"10.1145\/3052973.3053020"},{"key":"e_1_2_1_19_1","doi-asserted-by":"publisher","DOI":"10.1145\/1644038.1644060"},{"key":"e_1_2_1_20_1","doi-asserted-by":"publisher","DOI":"10.1109\/CRIS.2009.5071498"},{"key":"e_1_2_1_21_1","doi-asserted-by":"publisher","DOI":"10.1007\/11935308_4"},{"key":"e_1_2_1_22_1","volume-title":"Proceedings of the International Symposium on Precision Clock Synchronization for Measurement, Control and Communication (ISPCS\u201909)","author":"Ullmann Markus","unstructured":"Markus Ullmann and M. Vogeler . 2009. Delay attacks implication on NTP and PTP time synchronization . In Proceedings of the International Symposium on Precision Clock Synchronization for Measurement, Control and Communication (ISPCS\u201909) . Markus Ullmann and M. Vogeler. 2009. Delay attacks implication on NTP and PTP time synchronization. In Proceedings of the International Symposium on Precision Clock Synchronization for Measurement, Control and Communication (ISPCS\u201909)."},{"key":"e_1_2_1_23_1","doi-asserted-by":"publisher","DOI":"10.1109\/RTSS.2016.023"},{"key":"e_1_2_1_24_1","doi-asserted-by":"publisher","DOI":"10.1145\/3195182"},{"key":"e_1_2_1_25_1","volume-title":"Proceedings of the PES General Meeting.","author":"Wang Lei","year":"2008","unstructured":"Lei Wang , Javier Fernandez , Jon Burgett , Richard W. Conners , and Yilu Liu . 2008 . An evaluation of network time protocol for clock synchronization in wide area measurements . In Proceedings of the PES General Meeting. Lei Wang, Javier Fernandez, Jon Burgett, Richard W. Conners, and Yilu Liu. 2008. An evaluation of network time protocol for clock synchronization in wide area measurements. In Proceedings of the PES General Meeting."}],"container-title":["ACM Transactions on Cyber-Physical Systems"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/dl.acm.org\/doi\/10.1145\/3342048","content-type":"unspecified","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/dl.acm.org\/doi\/pdf\/10.1145\/3342048","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,6,18]],"date-time":"2025-06-18T00:43:25Z","timestamp":1750207405000},"score":1,"resource":{"primary":{"URL":"https:\/\/dl.acm.org\/doi\/10.1145\/3342048"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,7,31]]},"references-count":24,"journal-issue":{"issue":"3","published-print":{"date-parts":[[2019,7,31]]}},"alternative-id":["10.1145\/3342048"],"URL":"https:\/\/doi.org\/10.1145\/3342048","relation":{},"ISSN":["2378-962X","2378-9638"],"issn-type":[{"value":"2378-962X","type":"print"},{"value":"2378-9638","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,7,31]]},"assertion":[{"value":"2018-03-01","order":0,"name":"received","label":"Received","group":{"name":"publication_history","label":"Publication History"}},{"value":"2019-02-01","order":1,"name":"accepted","label":"Accepted","group":{"name":"publication_history","label":"Publication History"}},{"value":"2019-08-09","order":2,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}]}}