Samiran Bag

Retricoin: Bitcoin based on compact proofs of retrievability

Bitcoin [24] is a fully decentralized electronic cash system. The generation of the proof-of-work in Bitcoin requires large amount of computing resources. However, this huge amount of energy is wasted as one cannot make something useful out of it. In this paper, we propose a scheme called Retricoin which replaces the heavy computational proof-of-work of Bitcoin by proofs of retrievability that have practical benefits. To guarantee the availability of an important but large file, we distribute the segments of the file among the users in the Bitcoin network. Every user who wants to mine Bitcoins must store a considerable portion of this file and prove her storage to other peers in the network using proofs of retrievability. The file can be constructed at any point of time from the users storing their respective segments untampered. Retricoin is more efficient than the existing Permacoin scheme [23] in terms of storage overhead and network bandwidth required to broadcast the proof to the Bitcoin network. The verification time in our scheme is comparable to that of Permacoin and reasonable for all practical purposes. We also design an algorithm to let the miners in a group (or pool) mine collectively.

100% connectivity for location aware code based KPD in clustered WSN: merging blocks

Key management in wireless sensor networks (WSN) is a challenging task because of the stringent resource available to the nodes. As such key predistribution (KPD) is regarded as one of the best option for key management in WSN. This work analyzes an existing work by Simonova et al. that makes use of deployment knowledge where the deployment zone consists of clusters of nodes. Transversal design (TD) based KPD scheme of Lee and Stinson is used to distribute the keys in these clusters. However Simonova et al. points out that any KPD could have been used. This leads the current authors to investigates the applicability of Ruj and Roys Reed Solomon (RS) code based KPD , similar to the TD based KPD in distributing the key in each cluster. Much like the TD based KPD, the RS code based KPD does not offer full connectivity among nodes in the clusters amounting to lack of full connectivity in the amalgamated network. Full connectivity among nodes in each cluster and thus the entire network can be achieved by a deterministically merging strategy using exactly two nodes. This merging strategy is certainly better than a random approach by Chakrabarti et al. where the exact number of nodes being merged is not specified and does not ensure full connectivity. Since the scheme of Simonova et al. uses too many keys after amalgamation, a modified approach using Cluster Head (CH) is proposed to provide full communication in the network. Comparative study establishes the proposed Cluster Head design perform better than the KPD of Simonova et al. while proving the efficiency of the merging strategy.

A new key predistribution scheme for general and grid-group deployment of wireless sensor networks

Key predistribution for wireless sensor networks has been a challenging field of research because stringent resource constraints make the key predistribution schemes difficult to implement. Despite this, key predistribution scheme is regarded as the best option for key management in wireless sensor networks. Here, the authors have proposed a new key predistribution scheme. This scheme exhibits better performance than existing schemes of its kind. Moreover, our scheme ensures constant time of key establishment between two nodes. We provide some bounds on the resiliency of this scheme.Next, we use this new key predistribution scheme in a grid-group deployment of sensor nodes. The entire deployment zone is broken into square regions. The sensor nodes falling within a single square region can communicate directly. Sensor nodes belonging to different square regions can communicate by means of special nodes deployed in each of the square region. We measure the resiliency in terms of fraction of links disconnected as well as fraction of nodes and regions disconnected. We show that our key predistribution scheme when applied to grid-group deployment performs better than standard models in existence.

Highly Resilient Key Predistribution Scheme Using Transversal Designs and Reed Muller Codes For Wireless Sensor Network

Resource constraints of the nodes make security protocols difficult to implement. Thus key management is an important area of research in Wireless Sensor Networks (WSN). Key predistribution (kpd) which involves preloading keys in sensor nodes, has been considered as the best solution for key management when sensor nodes are battery powered and have to work unattended. This paper proposes a method to fix some loophole in an existing key predistribution scheme thereby enhancing the security of messages exchanged within a WSN. Here we use a model based on Reed Muller Codes to establish connectivity keys between sensor nodes. The model is then utilized to securely establish communication keys and exchange messages in a WSN designed on basis of two schemes using transversal designs for key predistribution. The combination of the key predistribution scheme and the connectivity model gives rise to highly resilient communication model with same connectivity between nodes as the chosen key predistribution scheme.

Key Predistribution in 3-Dimensional Grid-Group Deployment Scheme

We propose one deterministic key distribution schemes for wireless sensor networks, where the nodes are deployed in a 3 dimensional grid like structure.We use combinatorial designs for key predistribution in sensor nodes. Here the deplyment region is a 3-D grid. The whole deployment region is divided into smaller cubic zones. 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 depend upon the construction.

Two channel hopping schemes for jamming resistant wireless communication

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.

Jamming Resistant Schemes for Wireless Communication: A Combinatorial Approach

Jamming resistant communication mechanism is essential for reliable wireless communication. In this paper, we propose two channel hopping protocols using combinatorial designs for alleviating jamming attacks. One of these protocols is for unicast communication model and the other is aimed for multicast communication model. To the best of our knowledge, this is the first paper which uses combinatorial designs as a tool to solve the anti-jamming communication problem. Our protocols guarantee that the sender and receiver rendezvous within a finite amount of time to exchange information. In our protocol, each sender and receiver has a secret hopping sequence, instead of pairwise secret codes. Our unicast-communication protocol ensures that no two pairs of nodes collide over a single channel at the same time. Besides, the channels used by node-pairs for communication keep changing after every session making it infeasible for the adversary to anticipate the common channel to be used by a particular pair of nodes. We show these protocols using combinatorial designs performs better than existing anti-jamming protocol.

On the Application of Clique Problem for Proof-of-Work in Cryptocurrencies

In this work we propose a scheme that could be used as an alternative to the existing proof of workPoW scheme for mining in Bitcoin P2P network. Our scheme ensures that the miner must do at least a non-trivial amount of computation for solving the computational problem put forth in the paper and thus solving a PoW puzzle. Here, we have proposed to use the problem of finding the largest clique in a big graph as a replacement for the existing Bitcoin PoW scheme. In this paper, we have dealt with a graph having

SECURITY ENHANCED KEY PREDISTRIBUTION SCHEME USING TRANSVERSAL DESIGNS AND REED MULLER CODES FOR WIRELESS SENSOR NETWORKS

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