Cryptanalysis of the RSA-CEGD protocol
  Recently, Nenadi\'c et al. (2004) proposed the RSA-CEGD protocol for certified delivery of e-goods. This is a relatively complex scheme based on verifiable and recoverable encrypted signatures (VRES) to guarantee properties such as strong fairness and non-repudiation, among others. In this paper, we demonstrate how this protocol cannot achieve fairness by presenting a severe attack and also pointing out some other weaknesses. 
Juan M. E. Tapiador, Almudena Alcaide, Julio C. Hernandez-Castro,   Arturo Ribagorda