arXiv subjects

Kannan Srinathan

Publications and source records attributed to Kannan Srinathan.

6 recordsLinked to original sources

arXiv2026

Audit-or-Cast: Enforcing Honest Elections with Privacy-Preserving Public Verification

Electronic voting systems must balance public verifiability with voter privacy and coercion resistance. Existing cryptographic protocols typically achieve end-to-end verifiability by revealing vote distributions, relying on trusted clients, or enabling transferable receipts - design choices that often compromise trust or privacy in real-world deployments. We present ACE, a voting protocol that reconciles public auditability with strong privacy guarantees. The protocol combines a publicly verifiable, tally-hiding aggregation mechanism with an Audit-or-Cast challenge that enforces cast-as-intended even under untrusted client assumptions. Tallier-side re-randomization eliminates persistent links between voters and public records, yielding information-theoretic receipt-freeness assuming at least one honest tallier. We formalize the security of ACE and show that it simultaneously achieves end-to-end verifiability, publicly tally-hiding results, and strong receipt-freeness without trusted clients.

cs.CR↗

arXiv2022

Interlude: Balancing Chaos And Harmony For Fair and Fast Blockchains

Blockchains lie at the heart of Bitcoin and other cryptocurrencies that have shown great promise to revolutionize finance and commerce. Although they are gaining increasing popularity, they face technical challenges when it comes to scaling to support greater demand while maintaining their desirable security properties. In an exciting line of recent work, many researchers have proposed various scalable blockchain protocols that demonstrate the potential to solve these challenges. However, many of these protocols come with the assumptions of honest majority and symmetric network access which may not accurately reflect the real world where the participants may be self-interested or rational. Secondly, these works show that their protocol works in an ideal environment where each party has equal access to the network whereas different parties have varying latencies and network speeds. These assumptions may render the protocols susceptible to security threats in the real world, as highlighted by the literature focused on exploring game-theoretic attacks on these protocols. We propose a scalable blockchain protocol, Interlude, which comes with the typical security guarantees while focusing on game-theoretic soundness and network fairness. The novelty of Interlude is that it has a relatively simple design consisting of a sequence of parallel blocks containing disjoint transaction sets that can be mined quickly followed by a series block that is slow to mine and gives the honest parties in the network time to synchronize. Thus, between the chaos of parallel blocks, our blockchain protocol masquerades an interlude moment of harmony in series blocks that synchronize the network.

cs.CR↗

arXiv2015

Retrieving and Routing Quantum Information in a Quantum Network

In extant quantum secret sharing protocols, once the secret is shared in a quantum network (\textsc{qnet}) it can not be retrieved back, even if the dealer wishes that her secret no longer be available in the network. For instance, if the dealer is part of two \textsc{qnet}s, say $\mathcal{Q}_1$ and $\mathcal{Q}_2$ and subsequently finds that $\mathcal{Q}_2$ is more reliable than $\mathcal{Q}_1$, the dealer may wish to transfer all her secrets from $\mathcal{Q}_1$ to $\mathcal{Q}_2$. In this work we address this problem by designing a protocol that enables the source/dealer to bring back the information shared in the network, if desired. Unlike classical revocation, no-cloning-theorem automatically ensures that the secret is no longer shared in the network. The implications of our results are multi-fold. One interesting implication of our technique is the possibility of routing qubits in asynchronous \textsc{qnets}. By asynchrony we mean that the requisite data/resources are intermittently available (but not necessarily simultaneously) in the \textsc{qnet}. For example, we show that a source $S$ can send quantum information to a destination $R$ even though (a) $S$ and $R$ share no quantum resource, (b) $R$'s identity is {\em unknown}\/ to $S$ initially, (c) $S$ herself can be $R$ at a later date and/or in a different location to bequeath her information and (d) the path chosen for routing the secret may hit a dead-end due to resource constraints. Another implication of our technique is the possibility of using {\em insecure}\/ resources. For instance, it may safely store its private information with a neighboring organization without revealing data to the host and losing control over retrieving the data. Putting the two implications together, namely routing and secure storage, it is possible to envision applications like quantum mail (qmail) as an outsourced service.

quant-ph↗

arXiv2013

Efficient Range Reporting of Convex Hull

We consider the problem of reporting convex hull points in an orthogonal range query in two dimensions. Formally, let $P$ be a set of $n$ points in $\mathbb{R}^{2}$. A point lies on the convex hull of a point set $S$ if it lies on the boundary of the minimum convex polygon formed by $S$. In this paper, we are interested in finding the points that lie on the boundary of the convex hull of the points in $P$ that also fall with in an orthogonal range$[x_{lt},x_{rt}]\times{}[y_b, y_t]$. We propose a $O(n \log^{2} n) $ space data structure that can support reporting points on a convex hull inside an orthogonal range query, in time $O(\log^{3} n + h)$. Here $h$ is the size of the output. This work improves the result of (Brass et al. 2013) \cite{brass} that builds a data structure that uses $O(n \log^{2} n)$ space and has a $O(\log^{5} n + h)$ query time. Additionally, we show that our data structure can be modified slightly to solve other related problems. For instance, for counting the number of points on the convex hull in an orthogonal query rectangle, we propose an $O(n \log^{2}n)$ space data structure that can be queried upon in $O(\log^{3} n)$ time. We also propose a $O(n \log^{2} n) $ space data structure that can compute the $area$ and $perimeter$ of the convex hull inside an orthogonal range query in $O(\log^{3} n$) time.

cs.CG↗

arXiv2013

Exploring the Role of Logically Related Non-Question Phrases for Answering Why-Questions

In this paper, we show that certain phrases although not present in a given question/query, play a very important role in answering the question. Exploring the role of such phrases in answering questions not only reduces the dependency on matching question phrases for extracting answers, but also improves the quality of the extracted answers. Here matching question phrases means phrases which co-occur in given question and candidate answers. To achieve the above discussed goal, we introduce a bigram-based word graph model populated with semantic and topical relatedness of terms in the given document. Next, we apply an improved version of ranking with a prior-based approach, which ranks all words in the candidate document with respect to a set of root words (i.e. non-stopwords present in the question and in the candidate document). As a result, terms logically related to the root words are scored higher than terms that are not related to the root words. Experimental results show that our devised system performs better than state-of-the-art for the task of answering Why-questions.

cs.CL↗

arXiv2012

A New Look at Composition of Authenticated Byzantine Generals

The problem of Authenticated Byzantine Generals (ABG) aims to simulate a virtual reliable broadcast channel from the General to all the players via a protocol over a real (point-to-point) network in the presence of faults. We propose a new model to study the self-composition of ABG protocols. The central dogma of our approach can be phrased as follows: Consider a player who diligently executes (only) the delegated protocol but the adversary steals some private information from him. Should such a player be considered faulty? With respect to ABG protocols, we argue that the answer has to be no. In the new model we show that in spite of using unique session identifiers, if $n < 2t$, there cannot exist any ABG protocol that composes in parallel even twice. Further, for $n \geq 2t$, we design ABG protocols that compose for any number of parallel executions. Besides investigating the composition of ABG under a new light, our work also brings out several new insights into Canetti's Universal Composability framework. Specifically, we show that there are several undesirable effects if one deviates from our dogma. This provides further evidence as to why our dogma is the right framework to study the composition of ABG protocols.

cs.CR↗