Robust T-out-of-N proxy signature based on RSA cryptosystems

Proxy signature allows one user to delegate his signing capacity to other people. No proxy signature scheme based on the widespread RSA cryptosystem was proposed until 2003. However, the first RSA-based (t, n) threshold proxy signature scheme suffers from some drawbacks: (1) the original signer's private key can be derived and () the delegates' identities need to be chosen carefully. In this paper, we will propose an improved RSA-based (t, n) threshold proxy signature scheme with free-will identities and without the hell) of the trusted combiner. Moreover, the proposed scheme ensures the proxy signers' partial anonymity to provide the real proxy signers' privacy for safety, and no proxy signing key will be retrieved by the cooperation of the proxy signers.