Certificate-based fair exchange protocol of signatures from pairings

Chunxiang Gu, Yuefei Zhu, Yajuan Zhang

Zuhua Shao

Ming Chen, Kaigui Wu, Jie Xu

Changgen Peng

Fair exchange protocol is an important security protocol in E-commerce.A certificateless verifiably encrypted signature scheme is constructed based on certificateless cryptosystem.And based on verifiably encrypted signature scheme,a new certificateless fair exchange protocol is designed.The proposed protocol reduces the cost of the key-escrow and certificate management,and meets the validity,fairness,timeliness and optimization.

Zuhua Shao, Yipeng Gao

This paper proposes the first optimistic protocol to accomplish the fair exchange of standard Schnorr signatures in the chosen-key model, in which each participant is allowed to choose his Schnorr key pair freely without showing his knowledge of the private key. Besides solving the authentication problem of public keys, the protocol relaxes excessive trust on the adjudicator since the adjudicator needs to be trusted only by the signer. The protocol is secure against three types of inside adversaries under the DL assumption in the random oracle model. It suits much more the actual circumstances of the Internet.

Feng Bao, Robert Huijie Deng, Wenbo Mao

We present protocols for fair exchange of electronic data (digital signatures, payment and confidential data) between two parties A and B. Novel properties of the proposed protocols include: 1) offline trusted third party (TTP), i.e., TTP does not take part in the exchange unless one of the parties behaves improperly; 2) only three message exchanges are required in the normal situation; 3) true fair exchange, i.e., either A and B obtain each other's data or no party receives anything useful; no loss can be incurred to a party no matter how maliciously the other party behaves during the exchange. This last property is in contrast to previously proposed protocols with offline TTP ([1] and [21]), where a misbehaving party may get another party's data while refusing to send his document to the other party, and the TTP can provide affidavits attesting to what happened during the exchange. To our knowledge, the protocols presented here are the first exchange protocols which use offline TTP and at the same time guarantee true fair exchange of digital messages. We introduce a novel cryptographic primitive, called the Certificate of Encrypted Message Being a Signature (CEMBS), as the basic building block of the fair exchange protocols. It is used to prove that an encrypted message is a certain party's signature on a public file, without revealing the signature. We also give two examples to show in detail how the certificate can be constructed.