题 目: Improved Analysis on Ding et al.'s Outsourcing Protocols of Modular Exponentiations

主讲人：田呈亮，青岛大学计算机科学技术学院副教授

时 间：2020年5月20日 9:00

地 点：ZOOM云会议ID：3023985327

摘 要: We investigate the problem of securely outsourcing the modular exponentiations in cryptography to an untrusted server, and analyze the security and the efficiency of three privacy-preserving outsourcing protocols for exponentiations proposed in JCSS 2017. Based on lattice basis reduction techniques, we present heuristic polynomial-time and ciphertext-only attacks on these protocols which shows that the recommended parameters of their protocols can not assure the input privacy of the exponents. Meanwhile, according to different sizes of the problem in practice, we revise the parameter selection strategy in the original protocols to circumvent our attacks. Finally, we analyze the efficiency of the revised protocols with security parameters. Our theoretical analysis and experimental results demonstrate that, in practice, the outsourcing protocol of single modular exponentiation is invalid, the protocol of simultaneous modular exponentiations could suffer from poor efficiency and the protocol of multiple modular exponentiations becomes more efficient as the number of exponentiations increases.

主讲人简介：田呈亮，青岛大学计算机科学技术学院副教授，本硕毕业于西北大学，2013年7月于山东大学获得博士学位，2013.7-2015.8于中国科学院信工所信息安全国家重点实验室从事博士后研究。2015年9月加入青岛大学计算机科学技术学院，其中2018.12-2019.12美国堪萨斯大学访问学者。目前主要从事格密码学以及云计算/边缘计算中隐私保护问题研究，现主持国家自然科学青年基金、“十三五”国家密码发展基金、山东省自然科学基金青年项目、青岛市源头创新计划项目青年专项等纵向科研项目4项，以第一作者或通讯作者在IEEE TSC，Information Sciences, Science China:Information Sciences等国内外高水平计算机科学期刊发表SCI检索论文10余篇。