Schemes for Digital Signing Key Sharing

In the paper, we propose a new cryptographic notion, signing key sharing. Based on the notion, we present various types of signing key sharing schemes, such as proxy signature schemes, schemes for generating and sharing a signing key among a group, and (t,n) -threshold group proxy signature scheme. We also investigate the security conditions, the signer authentication and signer nonrepudiation of the proposed schemes. We find that the signer authentication can be altered into the signing key granting authentication and the signer nonrepudiation can be altered into the group nonrepudiation.