Pratyay Mukherjee
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pratyay85.bsky.social
Pratyay Mukherjee
@pratyay85.bsky.social
99 followers 62 following 29 posts
Principal Researcher @ Hashgraph | Interested in Cryptography and Security | https://pratyay.net/
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pratyay85.bsky.social
Great program #Nordicrypt_2025
claudiorlandi.bsky.social Claudio Orlandi @claudiorlandi.bsky.social · Jun 25
The program for the next NordiCrypt (30/06/2025) is online sites.google.com/view/nordicr...
June 25, 2025 at 3:03 PM
Reposted by Pratyay Mukherjee
eprint.ing.bot
Scalable Multiparty Computation from Non-linear Secret Sharing (Sanjam Garg, Abhishek Jain, Pratyay Mukherjee, Mingyuan Wang) ia.cr/2025/1007
Abstract. A long line of work has investigated the design of scalable secure multiparty computation (MPC) protocols with computational and communication complexity independent of the number of parties (beyond any dependence on the circuit size). We present the first unconditionally-secure MPC protocols for arithmetic circuits over {} with total computation 𝒪(|C|log|F|), where |C| and |F| denote the circuit and field size, respectively. Prior work could either achieve similar complexity only in {}, or required highly structured circuits, or expensive circuit transformations. To obtain our results, we depart from the prior approach of share packing in linear secret-sharing schemes; instead, we use an “unpacking” approach via {} secret sharing.
June 2, 2025 at 2:11 PM
pratyay85.bsky.social
New work on Verifiable Randomness
eprint.ing.bot ePrint Updates @eprint.ing.bot · May 21
InstaRand: Instantly Available and Instantly Verifiable On-chain Randomness (Jacob Gorman, Lucjan Hanzlik, Aniket Kate, Pratyay Mukherjee, Pratik Sarkar, Sri AravindaKrishnan Thyagarajan) ia.cr/2025/896
Abstract. Web3 applications, such as on-chain gaming, require unbiased and publicly verifiable randomness that can be obtained quickly and cost-effectively whenever needed. Existing services, such as those based on Verifiable Random Functions (VRF), incur network delays and high fees due to their highly interactive nature. FlexiRand [CCS 2023] addressed these problems by hiding the output of the VRF and using that as a seed to derive many randomnesses locally. These randomnesses are instantly available for usage. However, these randomnesses can not be verified independently (or instantly) without disclosing the seed, leaving scope for malicious actors to cheat. To solve this problem, we introduce a new notion, called instantly-verifiable VRF (iVRF), which enables the generation of many randomnesses from one VRF output seed, such that each of them is verifiable independently - this enables the first solution to cost − effectively generate randomnesses, such that they are instantly available and also independently/instantly verifiable. To instantiate we propose a generic construction called InstaRand - it combines any (possibly distributed) VRF at the server’s end with another VRF at the client’s end to construct an iVRF. Our specific instantiation uses the BLS-based GLOW-DVRF [Euro S&P 2021] at the server’s end and the DDH-based VRF of Goldberg et al. [RFC 2023] at the client’s end. We use the universal composability framework to analyze the security. Moreover, due to its generality, InstaRand can be instantiated with any post-quantum secure VRF to yield a post-quantum secure iVRF. Our experiments demonstrate that our instantiation of InstaRand is highly practical. The client incurs a one − time cost to generate the seed (server’s VRF output) by querying the GLOW-dVRF servers once. Once the seed is set up, the client locally generates the pseudorandom value on demand in 0.18 ms, avoiding the client-server round-trip delay. Each value can be independently verified in 0.22 ms. This yields a 400× improvement in terms of output generation and 20× improvement in verification cost over existing solutions. Image showing part 2 of abstract.
May 24, 2025 at 2:36 PM
pratyay85.bsky.social
Overleaf is down! Quintessential single point of failure!
May 14, 2025 at 6:33 AM
pratyay85.bsky.social
The AI fix feature on @overleaf.com is pretty cool actually, I am loving it so far :-)

(and it's not insanely expensive either)
April 14, 2025 at 7:18 AM
pratyay85.bsky.social
Why Bhutan is on the red list? 😶 #travelban
March 16, 2025 at 4:24 AM
pratyay85.bsky.social
Full version at eprint.iacr.org/2024/1713.pdf
February 26, 2025 at 1:16 PM
pratyay85.bsky.social
We instantiate the HE with class-group encryption, for which we show the crucial additional properties hold.

n/n
February 26, 2025 at 1:15 PM
pratyay85.bsky.social
In this work, we propose a technique by using homomorphic encryption (HE) with certain properties, which translates any sigma-ZKP for algebraic relation to support straight-line extraction, without repeating.

4/n
February 26, 2025 at 1:15 PM
pratyay85.bsky.social
For UC security of the entire scheme, the underlying ZKP must have a straight-line extractability. Existing techniques to achieve straight-line extractability rely on repeating the proof multiple times.

3/n
February 26, 2025 at 1:15 PM
pratyay85.bsky.social
Straightline extraction is a crucial property of ZKP, which is essential for UC security. E.g., an optimized threshold BLS signature may employ a non-interactive ZKP for partial verification (instead of pairing) to attest that Hash(msg) and g_2 have the same exponent (Chaum-Pederson proof).

2/n
February 26, 2025 at 1:15 PM
pratyay85.bsky.social
New paper PKC'25!

Joint work with Megan Chen (BU), Pousali Dey (ISI), Chaya Ganesh (IISC), Pratik Sarkar (Supra) and Swagata Sasmal (ISI)

1/n
February 26, 2025 at 1:15 PM
pratyay85.bsky.social
New paper on ePrint on Tracebale CCA-secure Encryptions!
eprint.ing.bot ePrint Updates @eprint.ing.bot · Feb 25
CCA-Secure Traceable Threshold (ID-based) Encryption and Application (Rishiraj Bhattacharyya, Jan Bormet, Sebastian Faust, Pratyay Mukherjee, Hussien Othman) ia.cr/2025/341
Abstract. A recent work by Boneh, Partap, and Rotem [Crypto’24] introduced the concept of traceable threshold encryption, in that if t or more parties collude to construct a decryption box, which performs decryptions, then at least one party’s identity can be traced by making a few black-box queries to the box. This has important applications, e.g., in blockchain mempool privacy, where collusion yields high financial gain through MEVs without any consequence - the possibility of tracing discourages collusion. Nevertheless, their definitions leave room for exploitation as they only achieve CPA security and do not consider inconsistency in decryption via different participating sets. This paper proposes stronger definitions of traceable threshold encryption, which supports CCA-security and consistency. Our main approach considers identity-based variants of traceable encryption (which we also define). It converts that to a CCA-secure construction, adapting two generic transformations, first using a one-time signature and then a fingerprinting code. We put forward two efficient instantiations of our identity-based scheme with different merits: our first construction is based on Boneh-Franklin IBE [Crypto’01] and has constant size ciphertexts but quadratic size public keys - this is proven secure based on XDH and BDDH. Our second construction is based on Boneh-Boyen IBE [Eurocrypt’04]. It supports both constant-size ciphertexts and constant-size public keys - this is proven secure based on a variant of the uber assumption over bilinear pairings. Our concrete analysis shows that the first construction’s ciphertext is much (~6x) smaller than the second construction. Finally, we extend the definitions to support consistency and achieve it by adjoining an efficient, non-interactive proof of correct encryption. Image showing part 2 of abstract.
February 26, 2025 at 1:07 PM
pratyay85.bsky.social
Kolkata Crypto Day (took place on 8th Dec at ISI Kolkata) slides are up!

sites.google.com/d/1Lz8Mff3Uj...
Google Drive: Sign-in
Access Google Drive with a Google account (for personal use) or Google Workspace account (for business use).
sites.google.com
February 13, 2025 at 7:09 AM
pratyay85.bsky.social
New work on ePrint!
eprint.ing.bot ePrint Updates @eprint.ing.bot · Feb 7
VITARIT: Paying for Threshold Services on Bitcoin and Friends (Lucjan Hanzlik, Aniket Kate, Easwar Vivek Mangipudi, Pratyay Mukherjee, Sri AravindaKrishnan Thyagarajan) ia.cr/2025/174
Abstract. Blockchain service offerings have seen a rapid rise in recent times. Many of these services realize a decentralized architecture with a threshold adversary to avoid a single point of failure and to mitigate key escrow issues. While payments to such services are straightforward in systems supporting smart contracts, achieving fairness poses challenges in systems like Bitcoin, adhering to the UTXO model with limited scripting capabilities. This is especially challenging without smart contracts, as we wish to pay only the required threshold of t + 1 out of the n servers offering the service together, without any server claiming the payment twice. In this paper, we introduce VITARIT 1, a novel payment solution tailored for threshold cryptographic services in UTXO systems like Bitcoin. Our approach guarantees robust provable security while facilitating practical deployment. We focus on the t-out-of-n distributed threshold verifiable random function (VRF) service with certain properties, such as threshold BLS signatures, a recently highlighted area of interest. Our protocol enables clients to request verifiable random function (VRF) values from the threshold service, triggering payments to up to t + 1 servers of the distributed threshold VRF. Our efficient design relies on simple transactions using signature verification scripts, making it immediately applicable in Bitcoin-like systems. We also introduce new tools and techniques at both the cryptographic and transaction layers, including a novel signature-VRF exchange protocol for standard constructions, which may be of independent interest. Addition- ally, our transaction flow design prevents malicious servers from claiming payments twice, offering broader implications for decentralized payment systems. Our prototype implementation shows that in the two-party interaction, the client takes 126.4 msec, and the server takes 204 msec, demonstrating practicality and deployability of the system Image showing part 2 of abstract.
February 7, 2025 at 10:58 AM
pratyay85.bsky.social
Yeah, I was wearing one ;)
December 30, 2024 at 5:41 PM
pratyay85.bsky.social
I love this idea!
thisone0verhere.bsky.social Jonathan Edward Durham @thisone0verhere.bsky.social · Dec 19
I recommend no fewer than 4 copies of any beloved book. A paperback for traveling and lending to friends, an eBook for reading with greasy snack fingers, an audio book so you know how the characters' names are actually pronounced, and a pristine hardcover to be buried with you like a pharaoh
December 20, 2024 at 3:40 AM
Reposted by Pratyay Mukherjee
smartcryptology.bsky.social
Submission deadline approaching for the IACR Communications in Cryptology (CiC).

Don’t miss your chance to contribute to this diamond open access journal.

Deadline: January 13, 2025 (AoE)

Details and submission guidelines: cic.iacr.org/callforpapers

#cryptography #iacr
December 13, 2024 at 10:18 AM
pratyay85.bsky.social
Thank you! Also hope you enjoyed the boat ride :-) #Asiacrypt2024
andreavbasso.bsky.social Andrea Basso @andreavbasso.bsky.social · Dec 11
It worked out well in the end (even if some people had to find a place that sells button downs last minute), thanks for organizing!
December 13, 2024 at 3:26 AM
pratyay85.bsky.social
Paul Kocher will deliver an IACR Distinguished Lecture tomorrow at #Asiacrypt2024
December 10, 2024 at 3:24 PM
pratyay85.bsky.social
Yeah, it was a last minute change unfortunately :-( sorry for any inconvenience (though, I have seen people not following it strictly), hope it worked ok?
December 10, 2024 at 11:33 AM
pratyay85.bsky.social
#Asiacrypt2024 Rump Session submission is open now...
asiacrypt.iacr.org/2024/rumpses...
December 10, 2024 at 11:28 AM
pratyay85.bsky.social
Adi's place?
December 9, 2024 at 4:38 AM
pratyay85.bsky.social
#Asiacrypt2024 (Important Change): The welcome reception will take place at the Calcutta Rowing Club (15, Dhakuria, Rabindra Sarobar, Kolkata, West Bengal 700029). Be aware that the venue *dress code* prohibits slippers/flip-flops/open chappals and shirts without collars
December 7, 2024 at 6:50 AM