International Association
for Cryptologic Research

Proxy signature is a kind of digital signature, in which a user called original signer can delegate his signing rights to another user called proxy signer and the proxy signer can sign messages on behalf of the original signer. Certificateless proxy signature (CLPS) means proxy signature in the certificateless setting in which there exists neither the certificate management issue as in traditional PKI nor private key escrow problem as in Identity-based setting. Up to now, a number of CLPS schemes have been proposed, but some of those schemes either lack formal security analysis or turn out to be insecure and others are less efficient because of using costly operations including bilinear pairings and map-to-point hashing on elliptic curve groups. In this paper, we formalize the definition and security model of CLPS schemes. We then construct a pairing-free CLPS scheme from the standard ECDSA and prove its security in the random oracle model under the discrete semi-logarithm problem’s hardness assumption as in the provable security result of ECDSA.