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 multirecipient 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.