Fair Exchange of Digital Signatures using RSA-based CEMBS and Offline STTP

TL;DR

This paper introduces RSA-based fair exchange protocols utilizing CEMBS and an offline semi-trusted third party to ensure secure, fair digital signature exchanges with confidentiality protections.

Contribution

It proposes three novel RSA-based fair exchange protocols leveraging CEMBS and an offline STTP, enhancing security and fairness in digital signature exchanges.

Findings

Three new fair exchange protocols are developed.

Protocols ensure confidentiality and fairness in signature exchange.

The role of STTP is limited to enhance security.

Abstract

One of the essential security services needed to safeguard online transactions is fair exchange. In fair exchange protocols two parties can exchange their signatures in a fair manner, so that either each party gain the other's signature or no one obtain anything useful. This paper examines security solutions for achieving fair exchange. It proposes new security protocols based on the "Certified Encrypted Message Being Signature" (CEMBS) by using RSA signature scheme. This protocol relies on the help of an "off-line Semi-Trusted Third Party" (STTP) to achieve fairness. They provide with confidential protection from the STTP for the exchanged items by limiting the role and power of the STTP. Three different protocols have been proposed. In the first protocol, the two main parties exchange their signatures on a common message. In the second protocol, the signatures are exchanged on two different messages. While in the third one, the exchange is between confidential data and signature.