Adaptive-CCA on OpenPGP Revisited

E-mail system has become one of the most important and popular Internet services. Instead of using traditional surface mail, we have the alternative of employing e-mail system which provides a reliable and efficient message delivery. However, in the electronic era, privacy, data integrity, and authentication requirements turn out to be especially unavoidable. Secure e-mail system specifications and software developments have been widely discussed in the past decade. Among which OpenPGP is a widespread and well known specification, and PGP becomes a famous implementation. But only limited security analyses on both theoretical and practical aspects about secure e-mail system has been considered previously. In this paper, new chosen ciphertext attacks against the latest version of OpenPGP are proposed with detailed analysis. Furthermore, a new vulnerability due to system version backward compatibility will be pointed out.