A secure electronic cash based on a certificateless group signcryption scheme

Many certificateless schemes have been proposed for different purposes, but as for as their applications in any electronic cash schemes there is still a lot of potential for strengthening the security aspect, and this paper is an attempt towards this. In this paper we propose a new type certificateless scheme which is applied for group oriented signcryption rather than a signature without using bilinear pairing, then a new E-cash system has been presented based on the proposed scheme. The salient feature of the proposed scheme is that any signcrypter of a group can signcrypt a document with the group manager and send it to the verifier. The verifier verifies the authenticity of the signcrypted text by using the group’s public parameters and cannot link a signcrypted text to the corresponding signcrypter. However, even the group manager or any signcrypter of that group alone cannot produce a valid signcrypted text. In case of any legal dispute, such as no repudiation of the signature, the group manager has the ability to reveal the identity of the signcrypter. The proposed scheme is secure against the indistinguishably chosen cipher text attack (IND-CCA). Unlinkability, unforgeability and traceability and its security are based on the two computationally hard problems, the Computational Diffie–Hellman Problem (CDHP) and Discrete Logarithmic Problem (DLP). The new scheme’s security analysis clearly suggests that it is very reliable to be used in security vulnerable applications in real life.