The study and analysis of the state-of-the-art on security in Peer-to-Peer (P2P) networks gives us many important insights regarding the lack of practical security mechanisms in such fully decentralized and highly dynamic networks. The major problems range from the absence of content authentication mechanisms, which address and assure the authenticity and integrity of the resources shared by networking nodes, to access control proposals, which provide authorization services. In particular, the combination of both, authentication and access control, within well-known P2P file sharing systems may involve several advances in the content replication and distribution processes. The aim of this thesis is to define, develop and evaluate a secure P2P content distribution scheme for file sharing scenarios. The proposal will be based on the use of digital certificates, similar to those used in the provision of public key authenticity. To carry out this proposal in such an environment, which does not count on a hierarchy of certification authorities, we will explore the application of non-conventional techniques, such as Byzantine agreement protocols and schemes based on ?proof-of-work.? Это и многое другое вы найдете в книге Secure Content Access and Replication in Peer-to-Peer Networks: A Certificate-based Approach (Esther Palomar)