arXiv subjects

Dipanwita Roy Chowdhury

Publications and source records attributed to Dipanwita Roy Chowdhury.

5 recordsLinked to original sources

arXiv2026

EnThM: Energy Theft Mitigation in Smart Grids using Hierarchical Verification of Metering Data

The advent of digital technologies has revolutionized traditional power distribution networks, transforming them into smart grids that are more reliable, efficient, and sustainable. Despite these advancements, electricity theft remains a significant threat to the effective operation of large electrical networks. To address this issue, we propose EnThM, a lightweight and communication-efficient scheme for real-time mitigation of power theft in smart grid systems. Our approach uses the hierarchical structure of the smart grid infrastructure to verify the authenticity of the metering data at multiple levels of the power distribution network. Our work focuses primarily on issues related to cryptographic security. The verification process involves statistically modeling the cumulative averages of the power usage data and applying rule-based checks on the aggregated power consumption at each level, while accounting for seasonal and daily consumption variations. The proposed method has been tested on benchmark consumption data, yielding high accuracy, efficient implementation, and real-time applicability.

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arXiv2024

Modeling Linear and Non-linear Layers: An MILP Approach Towards Finding Differential and Impossible Differential Propagations

Symmetric key cryptography stands as a fundamental cornerstone in ensuring security within contemporary electronic communication frameworks. The cryptanalysis of classical symmetric key ciphers involves traditional methods and techniques aimed at breaking or analyzing these cryptographic systems. In the evaluation of new ciphers, the resistance against linear and differential cryptanalysis is commonly a key design criterion. The wide trail design technique for block ciphers facilitates the demonstration of security against linear and differential cryptanalysis. Assessing the scheme's security against differential attacks often involves determining the minimum number of active SBoxes for all rounds of a cipher. The propagation characteristics of a cryptographic component, such as an SBox, can be expressed using Boolean functions. Mixed Integer Linear Programming (MILP) proves to be a valuable technique for solving Boolean functions. We formulate a set of inequalities to model a Boolean function, which is subsequently solved by an MILP solver. To efficiently model a Boolean function and select a minimal set of inequalities, two key challenges must be addressed. We propose algorithms to address the second challenge, aiming to find more optimized linear and non-linear components. Our approaches are applied to modeling SBoxes (up to six bits) and EXOR operations with any number of inputs. Additionally, we introduce an MILP-based automatic tool for exploring differential and impossible differential propagations within a cipher. The tool is successfully applied to five lightweight block ciphers: Lilliput, GIFT64, SKINNY64, Klein, and MIBS.

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arXiv2023

Security Analysis of WG-7 Lightweight Stream Cipher against Cube Attack

Welch--Gong (WG) is a hardware-oriented LFSR-based stream cipher. WG-7 is a version of the eStream submission Welch--Gong, used for RFID encryption and authentication purposes. It offers 80-bit cryptographic security. In modern days, almost all ciphers achieve the security by exploiting the nonlinear feedback structure. In this paper, we investigate the security of the nonlinear feedback-based initialization phase of the WG-7 stream cipher using the conventional bit-based division property of cube attack, by considering the cipher in a non-blackbox polynomial setting. In our work, we mount the cube attack using mixed-integer-linear-programming(MILP) models. The results of our attack enable us to recover the secret key of WG-7 after 20 rounds of initialization utilizing $2^{10}$ keystream bits in $2^{73}$ time. We show that our proposed attack takes significantly lower data complexity. To the best of our knowledge, our attack is the first one that investigates the security of the nonlinear feedback-based initialization phase of WG-7 cipher.

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arXiv2023

Efficient Algorithms for Modeling SBoxes Using MILP

Mixed Integer Linear Programming (MILP) is a well-known approach for the cryptanalysis of a symmetric cipher. A number of MILP-based security analyses have been reported for non-linear (SBoxes) and linear layers. Researchers proposed word- and bit-wise SBox modeling techniques using a set of inequalities which helps in searching differential trails for a cipher. In this paper, we propose two new techniques to reduce the number of inequalities to represent the valid differential transitions for SBoxes. Our first technique chooses the best greedy solution with a random tiebreaker and achieves improved results for the 4-bit SBoxes of MIBS, LBlock, and Serpent over the existing results of Sun et al. [25]. Subset addition, our second approach, is an improvement over the algorithm proposed by Boura and Coggia. Subset addition technique is faster than Boura and Coggia [10] and also improves the count of inequalities. Our algorithm emulates the existing results for the 4-bit SBoxes of Minalpher, LBlock, Serpent, Prince, and Rectangle. The subset addition method also works for 5-bit and 6-bit SBoxes. We improve the boundary of minimum number inequalities from the existing results for 5-bit SBoxes of ASCON and SC2000. Application of subset addition technique for 6-bit SBoxes of APN, FIDES, and SC2000 enhances the existing results. By applying multithreading, we reduced the execution time needed to find the minimum inequality set over the existing techniques.

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arXiv2009

A Secure and Efficient Protocol for Group Key agreement in Heterogeneous Environment

Secure group communication in heterogeneous environment is gaining popularity due to the advent of wireless and ubiquitous computing. Although a number of protocols for group key agreement have been proposed, most of them are not applicable in heterogeneous environment where a number of computationally limited nodes coexist with one or more computationally efficient nodes. Among the few existing protocols, where some fail to satisfy the key agreement properties, some are unable to handle the agreement for dynamic group. In this work, we propose a constant round group key agreement protocol for heterogeneous environment using polynomial interpolation. The protocol ensures both communication and computation efficiency by shifting the major computation load on powerful users, achieves true contributory key agreement property and dynamic handling of user join and leave. The security of the protocol has been analyzed under formal model. The comparison result shows considerable improvement in protocol efficiency compared to the existing ones.

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