Abstract
Certified e-mail is a particular case of fair exchange. TTPs play an important role in this kind of protocols and their reliability and security is a problem that needs to be addressed. In order to enhance the trust in non-repudiation services we propose TTPs that provide verifiable services, so users will get evidence of the TTPs operations. In this paper we will design a new certified e-mail protocol where the user confidence on what is happing when he invokes the TTP is enhanced.