This paper explores the relationships between the hard security concepts of identity and privacy on the one hand, and the soft security concepts of trust and reputation on the other hand. We specifically focus on two vulnerabilities that current trust and reputation systems have: the change of identity and multiple identities problems. As a result, we provide a privacy preserving solution to these vulnerabilities which integrates the explored relationships among identity, privacy, trust and reputation. We also provide a prototype of our solution to these vulnerabilities and an application scenario.

This work has been partially supported by CONSOLIDER-INGENIO 2010 under Grant CSD2007-00022, and projects TIN2008-4446, TIN2009-13839-C03-01 and PROMETEO/2008/051. Jose M. Such has received a Grant from Conselleria d'Empresa, Universitat i Ciencia de la Generalitat Valenciana (BFPI06/096).