Minicrypt Primitives with Algebraic Structure by Dr. Sikhar Patranabis

Location: CSA Seminar Hall (Room No. 254, First Floor)

Department of Computer Science and Automation
Department Seminar

Speaker : Dr. Sikhar Patranabis
Research Associate
Dept. of CSA
IISc

Title : Minicrypt Primitives with Algebraic Structure

Date : Tuesday, October 29, 2019

Time : 4:00 PM

Venue : CSA Seminar Hall (Room No. 254, First Floor)

Abstract

Algebraic structure lies at the heart of much of Cryptomania as we know it. An interesting question is the following: instead of building (Cryptomania) primitives from concrete assumptions, can we build them from simple Minicrypt primitives endowed with additional algebraic structure? In this work, we affirmatively answer this question by adding algebraic structure to the following Minicrypt primitives: one-way functions, weak unpredictable functions and weak pseudorandom functions. The algebraic structure that we consider is group homomorphism over the input/output spaces of these primitives. We show that these structured primitives can be used to construct several Cryptomania primitives in a generic manner. A few examples of such primitives include hash encryption, hinting PRGs, lossy trapdoor functions and maliciously secure OT/MPC in the plain/CRS model.

Our results make it substantially easier to show the feasibility of building many cryptosystems from novel assumptions in the future. In particular, we show how to realize any CDH/DDH-based protocol with certain properties in a generic manner from input-homomorphic weak unpredictable/pseudorandom functions, and hence, from any concrete assumption that implies the existence of these structured primitives.

Our results also allow us to categorize many cryptographic protocols based on which structured Minicrypt primitive implies them. In particular, endowing Minicrypt primitives with increasingly richer algebraic structure allows us to gradually build a wider class of cryptoprimitives. This seemingly provides a hierarchical classification of many Cryptomania primitives based on the “amount” of structure inherently necessary for realizing them.

Biography of the speaker

Sikhar Patranabis received his PhD in Computer Science with a specialization in cryptography from IIT Kharagpur, India. His research interests span all aspects of cryptography, with special focus on cryptographic complexity, encrypted analytics, and the design and implementation of real world cryptographic protocols.

Sikhar is currently visiting the CrIS Lab as a research associate, hosted by Dr. Arpita Patra. He will be joining as a postdoctoral researcher in the Applied Cryptography group at ETH Zürich, hosted by Dr. Kenny Paterson.
Sikhar was an IBM PhD fellow for the academic sessions 2016-17 and 2017-18. Prior to joining the PhD program, he completed his B.Tech from IIT Kharagpur, where he was the recipient of the President of India gold medal.

Host Faculty : Dr. Arpita Patra

ALL ARE WELCOME