Signatures for Network Coding

In communication networks, files commonly are separated into data packets and transmitted from the source node to a prescribed set of destination nodes by a method known as “store and forward”, in which data packets received are stored and then forwarded to the next node. Network coding has been proposed to replace the traditional “store and forward” model, and to improve the throughput and robustness of networks. With linear network coding, instead of copying and forwarding, intermediate nodes compute linear combinations of previously received information, and create and transmit a new packet to the next nodes. However, some malicious intermediate nodes may modify the data of packets and the recipients not can distinguish the corrupted packets from uncorrupted ones. This is known as a “pollution attack”. Homomorphic hashings and homomorphic signatures were proposed to provide cryptographic protection against pollution attacks. First, we present Krohn et al.’s homomorphic hashing schemes for rateless erasure codes. This paper presented six homomorphic signature schemes for network coding including three pairing-based homomorphic signature schemes, three RSA-based homomorphic signature schemes, and a signature scheme using a vector orthogonal to the message linear subspace. We then discuss and compare the memory and communication overhead of five of these homomorphic signature schemes. Finally, we point out flaws with some of these schemes, even though some security analysis has been presented, and we present solutions to prevent such attacks.