Efficient ID-based Threshold Signature Schemes without Pairings

The focus of this paper is to design an efficient and secure solution addressing the key escrow problem in ID-based signature schemes, i.e., the Private Key Generator (PKG) knows the user’s private key, which damages the essential requirement–“non-repudiation” property of signature schemes. In this paper, we proposed two ID-based threshold signature schemes, which both reach Girault’s trusted level 3, and in which there exists only one PKG in our ID-based threshold signature schemes. In particular, the second scheme has another good property: it does not require trusting any particular party at any time. Compared with the previous schemes, our schemes do not need to compute pairings, which make them be more efficient than those schemes. Furthermore, our ID-based signature schemes increase the availability of the signing agency and the difficulty for the adversary to learn the private key.