Identity-based online/offline signcryption for low power devices

Confidentiality and authentication are the basic security requirements for many cryptographic applications. In this paper, we propose an efficient identity-based online/offline signcryption scheme, which is very suitable for low power devices such as smart cards or mobile devices. Our scheme has the following advantages: (i) It does not need to authenticate a public key and fulfills both confidentiality and authentication simultaneously at a lower cost. (ii) Most of computations are carried out offline and online part is very efficient. (iii) It does not require the message and the receiver's identity in the offline stage. The message and the receiver's identity are only needed in the online stage. Compared with the existing schemes, our scheme have the great advantage of the offline storage and ciphertext length.