Network coding is promising to maximize throughput in various networking systems. Compared to normal network coding operated over large finite fields, XOR network coding has gained an increasing number of applications for its simplicity, especially in wireless networks. However, both types of network coding systems are vulnerable to pollution attacks in which the compromised forwarders inject polluted messages into the systems. Existing solutions to pollution attacks can protect only the normal network coding, but none of them is able to secure XOR network coding. In this paper, we propose an efficient scheme for securing XOR network coding against pollution attacks. Our scheme exploits probabilistic key pre-distribution and message authentication codes (MACs). In our scheme, the source appends multiple MACs to each message, where each MAC can authenticate only a part of the message and the parts authenticated by different MACs are overlapped. Thus, multiple forwarders can collaboratively verify different parts of messages using the MACs with their own shared keys. By carefully controlling the overlapping between the parts authenticated by different MACs, our scheme can filter polluted messages in a few hops with a high probability. To the best of our knowledge, this is the first solution to pollution attacks for XOR network coding. Experimental results show that it is 200 to 1000 times faster than existing ones, hence, it is particularly suitable for resource-constrained wireless networks.

Network coding provides the possibility to maximize network throughput and receives various applications in traditional computer networks, wireless sensor networks and peer-to-peer systems. However, the applications built on top of network coding are vulnerable to pollution attacks, in which the compromised forwarders can inject polluted or forged messages into networks. Existing schemes addressing pollution attacks either require an extra secure channel or incur high computation overhead. In this paper, we propose an efficient signature-based scheme to detect and filter pollution attacks for the applications adopting linear network coding techniques. Our scheme exploits a novel homomorphic signature function to enable the source to delegate its signing authority to forwarders, that is, the forwarders can generate the signatures for their output messages without contacting the source. This nice property allows the forwarders to verify the received messages, but prohibit them from creating the valid signatures for polluted or forged ones. Our scheme does not need any extra secure channels, and can provide source authentication and batch verification. Experimental results show that it can improve computation efficiency up to ten times compared to some existing one. In addition, we present an alternate lightweight scheme based on a much simpler linear signature function. This alternate scheme provides a tradeoff between computation efficiency and security.