Multi-Recipient Signcryption for Secure Wireless Group Communication

Secure group communication is significant for wireless and mobile computing. Overheads can be reduced efficiently when a sender sends multiple messages to multiple recipients using multi-recipient signcryption schemes. In this paper, we proposed the formal definition and security model of multi-recipient signcryption, presented the definition of reproducible signcryption and proposed security theorems for randomness reusing based multi-recipient signcryption schemes. We found that a secure reproducible signcryption scheme can be used to construct an efficient multi-recipient signcryption scheme which has the same security level as the underlying base signcryption scheme. We constructed a multi-recipient scheme which is provable secure in random oracle model assuming that the GDH problem is hard, based on a new BLS-type signcryption scheme. Overheads of the new scheme are only (n+1)/2n times of traditional ways when a sender sends different messages to n distinct recipients. It is more efficient than other known schemes. It creates a possibility for the practice of the public key cryptosystem in ubiquitous computing

An Improved User Authentication Protocol for Hierarchical Wireless Sensor Networks using Elliptic Curve Cryptography

In wireless sensor network, most of the queries are issued at the base station or gateway node the network. However, there are some critical WSN applications where real-time data are needed. But data at base station may not be real-time because of communication delay or periodic nature of data collection. So, real-time data can be accessed from the sensor nodes directly on demand. Before allowing the user to access real-time data from the sensor node, authentication of user must be ensured. But user authentication in case of wireless sensor network is a very critical task, as sensor nodes are deployed in unattached environment and are prone to possible hostile network attacks. Any authentication protocol in WSN must be designed keeping the fact that sensor nodes have limited computing power, memory, energy and communication capabilities. In this thesis, an improved user authentication protocol based on Elliptic Curve Cryptography (ECC) has been introduced for hierarchical wireless sensor networks (HWSN). This thesis shows that the ECC based protocol is suitable for wireless sensor networks, where higher security is demanded. Besides this the proposed scheme provides mutual authentication and a secret session key for communication between the user and the cluster head. It also provides an option for addition or replacement of cluster head in the network whenever there is a need. Then a comparative study of the proposed scheme with various existing is presented