Abstract: Partially blind signatures allow signers to include some common information (the date of issue, the value of electronic coins) negotiated by signers and users. This paper presents an efficient partially blind signatures scheme with provable security in the random oracle model. Our scheme uses a public algorithm to evolve the public keys and private keys which will be used during the partially blind signatures protocol. In such a manner the scheme has the same security as the underlying blind Okamoto-Schnorr signature without bringing out additional workload.