报告题目：New Lattice Two-Stage Sampling Technique and its Applications to Functional Encryption -Stronger Security and Smaller Ciphertexts

报告人：来齐齐 副教授 陕西师范大学

邀请人：刘振华

腾讯会议：437633156

时间：2021年12月11日（周六）14：30-16：30

报告摘要：Functional Encryption (FE) is a powerful generalization of public-key encryption (PKE), allowing more fine-grained information disclosure to a secret key holder. In FE, a secret key

is associated with a function

(in some class

), and ciphertext Enc

corresponds to some input

from the domain of

. Given a function key

and a ciphertext Enc

, the decryptor can only learn

, through running the decryption algorithm. During the past decade, there has been tremendous progress of FE for various function classes. However, all existing FE for general functions are still not good enough in security and efficiency. Hence, it is interesting and significant to consider how to construct much better FE constructions.

In this work, we focus on FE from lattices. Particularly, this work first proposes a new lattice two-stage sampling technique, generalizing the prior two-stage sampling method of Gentry, Peikert, and Vaikuntanathan (STOC '08). Then, by using our new technique as a key building block, we can significantly improve security and efficiency of the current state of the arts of simulation-based functional encryption. Particularly, our functional encryption achieves (Q,poly) simulation-based semi-adaptive security that allows arbitrary pre- and post-challenge key queries, and has succinct ciphertexts with only an additive O(Q) overhead. Additionally, our two-stage sampling technique can derive new feasibilities of indistinguishability-based adaptively-secure IB-FE for inner products and semi-adaptively-secure AB-FE for inner products, breaking several technical limitations of the recent work by Abdalla, Catalano, Gay,and Ursu (Asiacrypt '20).

个人简介：来齐齐，陕西师范大学计算机科学学院，副教授，硕士生导师。研究方向为后量子安全的公钥密码方案的设计与分析。2015年获得西安电子科技大学密码学专业博士学位，2011年获得西安电子科技大学密码学专业硕士学位。在国际密码学会顶级会议EUROCRYPT、PKC等发表多篇论文。主持国家自然科学基金面上项目和青年项目各1项。