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PIYUSH KUMAR SHARMA

Email: piyushs at iiitd dot ac dot in

I am a PhD student in Computer Science and Engineering (CSE) department at Indraprastha Institute of Information Technology, Delhi (IIITD). I am advised by Dr. Sambuddho Chakravarty (IIITD). I also collaborate with Dr. H.B. Acharya (Rochester Institute of Technology, New York).
I will be working as a postdoc with Dr. Claudia Diaz at COSIC, KU Leuven later this year.
My research interests broadly lie in Security, Privacy, Systems and Networks.

Recent News

July 2020

2 papers presented at PoPETS 2020

November 2020                           

Successfully passed the PhD Comprehensive exam

Committee Members:
External: Prof. Angelos Keromytis (Georgia Tech, USA)
Internal: Dr. Arun Balaji Buduru (IIIT Delhi, India),
Dr. Vinayak Naik (BITS Pilani, Goa campus,India)

February 2021

Will be joining KU, Leuven as a post-doc

Will be working with Prof. Claudia Diaz, who heads the Privacy Technologies team at COSIC.

February 2021                         

Paper accepted at AsiaCCS 2021 

Research Projects

SiegeBreaker: SDN Based Practical Decoy Routing System [PETS 2020]

Decoy Routing, the use of routers (rather than end hosts) as proxies, shows great promise as an anti-censorship mechanism. To use a Decoy Router, the user sends specially crafted packets, apparently to an uncensored website. En route, the packets encounter the Decoy Router (beyond the network boundaries of the censor), which identifies them (using a covert cryptographic handshake), decrypts their content, and proxies them to their true destination. However, Decoy Routing requires routers able to perform complicated operations (detecting secret handshakes, decrypting packets, etc). This requirement is a major challenge: commercial routers are limited in flexibility, and existing Decoy Router implementations (on commodity servers) are unsuitable for carrier-grade deployments.

In this project we aim to build a practical Decoy Routing prototype, SiegeBreaker. SiegeBreaker is built on an SDN architecture, and divides the responsibilities for Decoy Routing among three entities – the SDN switch that simply forwards packets, the SDN controller that identifies the secret handshake, and a hidden proxy server to which the switch eventually forwards the clients’ request (at the controller’s behest), which then communicates to the censored site. In other words, neither does the switch/router perform any additional computations like identification of covert handshake packets, and nor does the proxy server deal with the cross-traffic (flows that do not require Decoy Routing).

Accessing The Censored Web By Utilizing Instant Messaging Channels [AsiaCCS 2021]

Recent anti-censorhip systems have relied on a common blocking resistance strategy i.e., incurring collateral damage to the censoring regimes, if they attempt to restrict such systems. However, despite being promising, systems built on such strategies pose additional challenges, viz., deployment limitations, cost overheads, poor QoS etc. These challenges prevent their wide scale adoption.

Thus, we propose a new anti-censorship system, Camoufler, that overcomes aforementioned challenges, while still maintaining similar blocking resistance. Camoufler leverages Instant Messaging (IM) platforms to tunnel client's censored content. This content (encapsulated inside IM traffic) is transported to the Camoufler server (hosted in a free country), which proxies it to the censored website. However, the eavesdropping censor would still observe regular IM traffic being exchanged between the IM peers. Thus, utilizing IM channels as-is for transporting traffic provides unobservability, while also ensuring good QoS, due to its inherent properties such as low-latency message transports. Moreover, it does not pose new deployment challenges. Performance evaluation of Camoufler, implemented on five popular IM apps indicate that it provides sufficient QoS for web browsing. E.g., the median time to render the homepages of Alexa top-1k sites was recorded to be about 3.6s, when using Camoufler implemented over Signal IM application.

Anonymous End-to-End Voice Calling [PETS 2020] 

Anonymous VoIP calls over the Internet holds great significance for privacy-conscious users, whistle-blowers and political activists alike. Prior research deems popular anonymization systems like Tor unsuitable for providing the requisite performance guarantees that real-time applications like VoIP need. Their claims are backed by studies that may no longer be valid due to constant advancements in Tor. Moreover, we believe that these studies lacked the requisite diversity and comprehensiveness. Thus, conclusions from these studies, led them to propose novel and tailored solutions. However, no such system is available for immediate use. Additionally, operating such new systems would incur significant costs for recruiting users and volunteered relays, to provide the necessary anonymity guarantees.

It thus becomes an imperative that the exact performance of VoIP over Tor be quantified and analyzed, so that the potential performance bottlenecks can be amended. We thus conducted an extensive empirical study across various in-lab and real world scenarios to shed light on VoIP performance over Tor.

Analyzing and Evading Censorship Mechanisms in India [IMC 2018]
(Work in collaboration with Dr. Devashish Gosain)

In this work we present a detailed study of the Internet censorship in India. We consolidated a list of potentially blocked websites from various public sources to assess censorship mechanisms used by nine major ISPs.

To begin with, we demonstrate that existing censorship detection tools such as OONI are inaccurate. We thus developed various techniques and heuristics to correctly assess censorship and study the underlying mechanism involved in these ISPs. At every step we corroborated our finding manually to test the efficacy of our approach, a step largely ignored by others. We fortify our findings by adjudging the coverage and consistency of censorship infrastructure, broadly in terms of average number of network paths and requested domains the infrastructure surveils.

Our results indicate a clear disparity among the ISPs, on how they install censorship infrastructure. For instance, in Idea network we observed the censorious middleboxes on over 90% of our tested intra-AS paths whereas for Vodafone, it is as low as 2.5%. We conclude our research by devising our own anti-censorship strategies, that does not depend on third party tools (like proxies, Tor and VPNs etc.). We managed to anti-censor all blocked websites in all ISPs under test.

On the Defendability of National Cyberspace [LCN 2020]
(Work in collaboration with Dr. Devashish Gosain)

National governments know the Internet as both a blessing and a headache. On the one hand, it unlocks great economic and strategic opportunity. On the other hand, government, military, or emergency-services become vulnerable to scans (Shodan), attacks (DDoS from botnets like Mirai), etc., when made accessible on the Internet. How hard is it for a national government to effectively secure its entire cyberspace? We approach this problem from the view that a coordinated defense involves monitors and access control (firewalls etc.) to inspect traffic entering or leaving the country, as well as internal traffic. In several case studies, we consistently find a natural Line of Defense — a small number of Autonomous Systems (ASes) that intercept most (> 95%) network paths in the country. We conclude that in many countries, the structure of the Internet actually makes it practical to build a nation-scale cordon, to detect and filter cyber attacks.

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PUBLICATIONS


[+] Camoufler: Accessing The Censored Web By Utilizing Instant Messaging Channels [pdf]
      Piyush Kumar Sharma, Devashish Gosain, Sambuddho Chakravarty
      To appear in proceedings of ACM AsiaCCS 2021.

[+] The Road Not Taken: Re-thinking the Feasibility of Voice Calling Over Tor [pdf][video]
      Piyush Kumar Sharma, Shashwat Chaudhary*, Nikhil Hassija*, Mukulika Maity, and Sambuddho Chakravarty
      In Proceedings of Privacy Enhancing Technologies Symposium (PETS) 2020. (* Equal contribution of authors)

[+] SiegeBreaker: An SDN Based Practical Decoy Routing System [pdf][video
      Piyush Kumar Sharma, Devashish Gosain, Himanshu Sagar, Chaitanya Kumar, Aneesh Dogra, Vinayak Naik, H.B.
      Acharya, and Sambuddho Chakravarty
      In Proceedings of Privacy Enhancing Technologies Symposium (PETS) 2020.

[+] Maginot Lines and Tourniquets : On the Defendability of National Cyberspace [pdf]
      Devashish Gosain, Madhur Rawat, Piyush Kumar Sharma, H.B Acharya
      In proceedings of Local Computer Networks (LCN) 2020.

[+] Where The Light Gets In: Analyzing Web Censorship Mechanisms in India. [pdf]
      Tarun Kumar Yadav*, Akshat Sinha*, Devashish Gosain*, Piyush Kumar Sharma, Sambuddho Chakravarty
      In proceedings of ACM Internet Measurement Conference (IMC) 2018. (*Shared First Authorship).

[+] SiegeBreaker : SDN Based Decoy Routing System [pdf]
      Piyush Kumar Sharma, Chaitanya Kumar, Aneesh Dogra, Vinayak Naik, H.B. Acharya, Sambuddho Chakravarty
      WIP published in ACSAC 2017.

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