Broadcast encryption with dealership

In this paper, we introduce a new cryptographic primitive called broadcast encryption with dealership. This notion, which has never been discussed in the cryptography literature, is applicable to many realistic broadcast services, for example subscription-based television service. Specifically, the new primitive enables a dealer to bulk buy the access to some products (e.g., TV channels) from the broadcaster, and hence, it will enable the dealer to resell the contents to the subscribers with a cheaper rate. Therefore, this creates business opportunity model for the dealer. We highlight the security consideration in such a scenario and capture the security requirements in the security model. Subsequently, we present a concrete scheme, which is proven secure under the decisional bilinear Diffie-Hellman exponent and the Diffie-Hellman exponent assumptions

Security Framework for Decentralized Shared Calendars

International audienceWe propose a security framework for Decentralized Shared Calendar. The proposed security framework provides confidentiality to replicated shared calendar events and secures the commu- nication between users. It is designed in such a way that DeSCal preserves all of its characteristic features like fault-tolerance, crash recovery, availability and dynamic access control. It has been implemented on iPhone OS.Nous proposons un protocole de sécurité pour des agendas partagés dont la gestion de données est complètement décentralisée. Dans ce protocole, nous assurons à la fois (i) la confidentialité du contenu répliqué et (ii) la sécurité de communication entre les utilisateurs. Comme nous utilisons une réplication complête de données, notre protocole préserve toutes les caractéristiques d'une telle réplication, à savoir : la tolérance aux pannes et la reprise après panne. Pour valider notre solution, nous avons implémenté un prototype sur des mobiles tournant sous le système iPhone OS

SECURITY RESEARCH FOR BLOCKCHAIN IN SMART GRID

Smart grid is a power supply system that uses digital communication technology to detect and react to local changes for power demand. Modern and future power supply system requires a distributed system for effective communication and management. Blockchain, a distributed technology, has been applied in many fields, e.g., cryptocurrency exchange, secure sharing of medical data, and personal identity security. Much research has been done on the application of blockchain to smart grid. While blockchain has many advantages, such as security and no interference from third parties, it also has inherent disadvantages, such as untrusted network environment, lacking data source privacy, and low network throughput.In this research, three systems are designed to tackle some of these problems in blockchain technology. In the first study, Information-Centric Blockchain Model, we focus on data privacy. In this model, the transactions created by nodes in the network are categorized into separate groups, such as billing transactions, power generation transactions, etc. In this model, all transactions are first encrypted by the corresponding pairs of asymmetric keys, which guarantees that only the intended receivers can see the data so that data confidentiality is preserved. Secondly, all transactions are sent on behalf of their groups, which hides the data sources to preserve the privacy. Our preliminary implementation verified the feasibility of the model, and our analysis demonstrates its effectiveness in securing data source privacy, increasing network throughput, and reducing storage usage. In the second study, we focus on increasing the network’s trustworthiness in an untrusted network environment. A reputation system is designed to evaluate all node’s behaviors. The reputation of a node is evaluated on its computing power, online time, defense ability, function, and service quality. The performance of a node will affect its reputation scores, and a node’s reputation scores will be used to assess its qualification, privileges, and job assignments. Our design is a relatively thorough, self-operated, and closed-loop system. Continuing evaluation of all node’s abilities and behaviors guarantees that only nodes with good scores are qualified to handle certain tasks. Thus, the reputation system helps enhance network security by preventing both internal and external attacks. Preliminary implementation and security analysis showed that the reputation model is feasible and enhances blockchain system’s security. In the third research, a countermeasure was designed for double spending. Double spending is one of the two most concerned security attacks in blockchain. In this study, one of the most reputable nodes was selected as detection node, which keeps checking for conflict transactions in two consecutive blocks. Upon a problematic transaction was discovered, two punishment transactions were created to punish the current attack behavior and to prevent it to happen in future. The experiment shows our design can detect the double spending effectively while using much less detection time and resources