Efficient Verifiably Encrypted Signature and Partially Blind Signature from Bilinear Pairings

Verifiably encrypted signatures are used when Alice wants to sign a message for Bob but does not want Bob to possess her signature on the message until a later date. Such signatures are used in optimistic contact signing to provide fair exchange. Partially blind signature schemes are an extension of blind signature schemes that allows a signer to sign a partially blinded message that include preagreed information such as expiry date or collateral conditions in unblinded form. These signatures are used in applications such as electronic cash (e-cash) where the signer requires part of the message to be of certain form. In this paper, we propose a new verifiably encrypted signature scheme and a partially blind signature scheme, both based on bilinear pairings. We analyze the security and efficiency of these schemes and show that they are more efficient than the previous schemes of their kinds.