Review on variants of reliable and security aware peer to peer content distribution using network coding

Content distribution system can transmit large files rapidly between multiple users, and it has become the most widely used in internet. Network coding is a technique which can enhance the performance and reliability of P2P networks. P2P content distribution networks can suffer from malicious participants that corrupt content. Existing systems verify distributed blocks of file with conventional encryption techniques and hash functions. However, these techniques do not apply well to more well-designed schemes that use network coding techniques for efficient content distribution. In such networks, it is necessary that some security mechanisms will be applied with the aim of avoiding attacks based on non authorized content modifications. Some threats like pollution attack, entropy attack, jamming attack degrade the performance of content delivery in P2P networks. To identify the polluted blocks is difficult and needs the use of homomorphic hashing functions, whose implementation is expensive. This paper review a security scheme for network coding that reduces the cost of verifying blocks on the way before decoding while efficiently preventing the propagation of malicious blocks. In this scheme, users not only cooperate to distribute the content, but users also cooperate to protect themselves against malicious users by informing affected nodes when a malicious block is found. In this paper we analyze and study such cooperative security schemes.