Speaker:Tian Chengliang is an associate professor at College of Computer Science & Technology of Qingdao University. He obtained bachelor’s and master’s degree from Northwest University, obtained doctor's degree from Shandong University in July 2013, and engaged in post-doctoral research in the State Key Laboratory of Information Security at Institute of Information Engineering CAS from July 2013 to August 2015. In September 2015, he joined the College of Computer Science & Technology of Qingdao University. He was a visiting scholar of Kansas University from December 2018 to December 2019. Currently, he is mainly engaged in the research of lattice-based cryptography and privacy protection in cloud computing/edge computing, and he is presiding over four research projects, including the National Natural Science Youth Fund project etc. He has published more than 10 papers in high level journals including IEEE TSC, Information Science, Science China: Information Sciences etc.

Date:May 13, 2020

Time:9:00

Location: Welcome to ZOOM meeting, ID:3023985327

Abstract:

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.

Inviter:Prof. Zhuang Jincheng

Edited by:Xu Zeyu