India is the largest democracy by population and has one of the largest deployments of e-voting in the world for national elections. However, the e-voting machines used in India are not end-to-end (E2E) verifiable. The inability to verify the tallying integrity of an election by the public leaves the outcome open to disputes. E2E verifiable e-voting systems are commonly regarded as the most promising solution to address this problem, but they had not been implemented or trialed in India. It was unclear whether such systems would be usable and practical to the Indian people. Previous works such as Helios require a set of tallying authorities (TAs) to perform the decryption and tallying operations, but finding and managing TAs can prove difficult. This paper presents a TA-free E2E verifiable online voting system based on the DRE-ip protocol. In collaboration with the local authority of New Town, Kolkata, India, we conducted an online voting trial as part of the 2022 Durga Puja festival celebration, during which residents of New Town were invited to use mobile phones to vote for their favorite pujas (festival decorations) in an E2E verifiable manner. 543 participants attended the Durga Puja trial and 95 of them provided feedback by filling in an anonymous survey after voting. Based on the voter feedback, participants generally found the system easy to use. This was the first time that an E2E online voting system had been built and tested in India, suggesting its feasibility for non-statutory voting scenarios.

Hashed Timelock Contract (HTLC) in Lightning Network is susceptible to agriefing attack. An attacker can block several channels and stall payments by mounting this attack. A state-of-the-art countermeasure, Hashed Timelock Contract with Griefing-Penalty (HTLC-GP) is found to work under the classical assumption of participants being either honest or malicious but fails for rational participants. To address the gap, we introduce a game-theoretic model for analyzing griefing attacks inHTLC. We use this model to analyze griefing attacks inHTLC-GPand conjecture that it is impossible to design an efficient protocol that will penalize a malicious participant with the current Bitcoin scripting system. We study the impact of the penalty on the cost of mounting the attack and observe thatHTLC-GPisweakly effectivein disincentivizing the attacker in certain conditions. To further increase the cost of attack, we introduce the concept ofguaranteed minimum compensation, denoted as$\zeta $, and modifyHTLC-GPinto$\mathrm {HTLC{-}GP}^{\zeta }$. By experimenting on several instances of Lightning Network, we observe that the total coins locked in the network drops to 28% for$\mathrm {HTLC{-}GP}^{\zeta }$, unlike inHTLC-GPwhere total coins locked does not drop below 40%. These results justify that$\mathrm {HTLC{-}GP}^{\zeta }$is better thanHTLC-GPto counter griefing attacks.

The Traveling Tournament Problem(TTP) is a combinatorial optimization problem where we have to give a scheduling algorithm which minimizes the total distance traveled by all the participating teams of a double round-robin tournament maintaining given constraints. Most of the instances of this problem with more than ten teams are still unsolved. By definition of the problem the number of teams participating has to be even. There are different variants of this problem depending on the constraints. In this problem, we consider the case where number of teams is a multiple of four and a team can not play more than two consecutive home or away matches. Our scheduling algorithm gives better result than the existing best result for number of teams less or equal to 32.

Jamming resistance is crucial for reliable wireless communication. Most of the existing schemes offering counter-measures of jamming depend on the use of a secret key shared between the communicating devices. This secret key is used to generate a random hopping sequence. The message-sender and the message-receiver hop over different wireless channels depending upon this generated sequence. But such anti-jamming mechanisms fail in broadcast communication scenarios where the number of receivers do not remain the same. There are other strategies like Uncoordinated Frequency Hopping (UFH). But this scheme has a major disadvantage that under this scheme a sender and a receiver need to hop randomly over a number of channels and they can only communicate a message only if they meet over the same channel at any instant. This limitation makes communication under UFH very slow. We propose two schemes for unicast wireless communication in presence of a jammer. Our scheme is applicable to such scenarios where one party sends messages to one recipients through wireless channels. This scheme does not require any secret keys shared between the communicating devices or users. Despite that, the communicating parties can hop over the available wireless channels and thus evading the jammer. We used combinatorial design for designing these channel hopping schemes. These schemes guaranty that in any time slot the sender and the receiver must meet on some channel every time.

We propose a new grid-group deployment scheme in wireless sensor networks. We use combinatorial designs for key predistribution in sensor nodes. The deployment region is divided into square regions. The predistribution scheme has the advantage that all nodes within a particular region can communicate with each other directly and nodes which lie in a different regions can communicate via special nodes called agents which have more resources than the general nodes. The number of agents in a region is always three, whatever the size of the network. We give measures of resiliency taking the Lee distance into account. Apart from considering the resiliency in terms of fraction of links broken, we also consider the resiliency as the number of nodes and regions disconnected when some sensor are compromised. This second measure, though very important, had not been studied so far in key predistribution schemes which use deployment knowledge. We find that the resiliency as the fraction of links compromised is better than existing schemes. The number of keys preloaded in each sensor node is much less than all existing schemes and nodes are either directly connected or connected via two hop paths. The deterministic key predistribution schemes result in constant-time computation overhead for shared key discovery and path key establishment.

Summarising recent results, we emphasise the importance of studying the. properties of multiples of primitive polynomials and their products in connection with fast correlation attacks on LFSR-based stream cipher systems. These results may serve as an important tool for future design of stream cipher systems with LFSR as a main design block. Also the security of such existing systems needs to be reviewed in light of these results. Finding an efficient polynomial time algorithm to get the least degree t-nomial multiple of the primitive polynomials and their products is still an open problem.