On the Practical and Security Issues of Batch Content Distribution Via Network Coding

File distribution via network coding has received a lot of attention lately. However, direct application of network coding may have security problems. In particular, attackers can inject "faked" packets into the file distribution process to slow down the information dispersal or even deplete the network resource. Therefore, content verification is an important and practical issue when network coding is employed. When network coding is used, it is infeasible for the source of the content to provide all the hash values or signatures required for verification, and hence the traditional "hash-and-sign" methods are no longer applicable. Recently, a new on-the-fly verification technique is proposed by Krohn et al. for rateless erasure codes. However, their scheme requires a large number of hash values to be distributed in advance, and all of them are needed to verify even for a single packet. We propose a new batch delivery and verification scheme that is similar to the classical scenario where the authentication information of a message is embedded with the message and is sufficient for the verification purpose. We investigate how our technique can be applied when random linear network coding is employed, and show that both the computational and the bandwidth overhead can be greatly reduced by using a variant of the random network coding. We further show by simulation that this variant is sufficiently effective in practice.