2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/209429Recently, Nenadić 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.8 pages, 1 figureCryptography and Securitytext