A P2P content authentication protocol based on Byzantine agreement

One of the main advantages of peer-to-peer (P2P) systems is their capability to offer replicas of the same content at various locations. This allows to access contents even when some nodes are disconnected. However, this high degree of redundancy implies that it is necessary to apply some security mechanisms in order to avoid attacks based on non-authorized content modification. In this paper, we propose a content authentication protocol for pure P2P systems. Under certain restrictions, our scheme provides guarantees that a content is authentic, i.e. it has not been altered, even if it is a replica of the original and the source has lost control over it. Our proposal relies on a set of peers playing the role of a certification authority, for it is unrealistic to assume that appropriate trusted third parties can be deployed in such environments. Finally, we discuss some of its security properties through several attack scenarios.