Seminars

View all Seminars  |  Download ICal for this event

Asymptotically Free Broadcast in Constant Expected Time via Packed VSS

Series: IISc-CRYPTO Seminars

Speaker: Shravani Patil Ph.D student Department Computer Science and Automation IISc, Bangalore

Date/Time: Nov 03 17:00:00

Location: Microsoft Teams - ON-LINE

Abstract:
Broadcast is an essential primitive for secure computation. We focus in this paper on optimal resilience (i.e., when the number of corrupted parties t is less than a third of the computing parties n), and with no setup or cryptographic assumptions.

While broadcast with worst case t rounds is impossible, it has been shown [Feldman and Micali STOC88, Katz and Koo CRYPTO06] how to construct protocols with expected constant number of rounds in the private channel model. However, those constructions have large communication complexity, specifically O(n2L + n6log n) expected number of bits transmitted for broadcasting a message of length L. This leads to a significant communication blowup in secure computation protocols in this setting.

In this paper, we substantially improve the communication complexity of broadcast in constant expected time. Specifically, the expected communication complexity of our protocol is O(nL + n4log n). For messages of length L = Ω(n3log n), our broadcast has no asymptotic overhead (up to expectation), as each party has to send or receive O(n3log n) bits. We also consider parallel broadcast, where n parties wish to broadcast L bit messages in parallel. Our protocol has no asymptotic overhead for L = Ω(n2log n), which is a common communication pattern in perfectly secure MPC protocols. For instance, it is common that all parties share their inputs simultaneously at the same round, and verifiable secret sharing protocols require the dealer to broadcast a total of O(n2log n) bits.

As an independent interest, our broadcast is achieved by a packed verifiable secret sharing, a new notion that we introduce. We show a protocol that verifies O(n) secrets simultaneously with the same cost of verifying just a single secret. This improves by a factor of n the state-of-the-art.

Speaker Bio:
Shravani Patil is a Ph.D student at Computer Science and Automation department at IISc, Bangalore working under the guidance of Dr. Arpita Patra. Her broad area of research is Secure Multi-party Computation, primarily focussing on information theoretically secure protocols for secure computation and broadcast. Microsoft teams link: https://teams.microsoft.com/l/meetup-join/19%3ameeting_OWVkNDEwNGUtMDQ3ZC00NzFmLWI5YzUtYmM4Yzc0ZTI5MGZk%40thread.v2/0?context=%7b%22Tid%22%3a%226f15cd97-f6a7-41e3-b2c5-ad4193976476%22%2c%22Oid%22%3a%22f8aaf4da-ac16-401f-a953-eeb416835728%22%7d

Host Faculty: Prof. Arpita Patra