Security analysis and improvement of a tag encoding authentication scheme for network coding

A tag encoding authentication scheme for network coding proposed by Wu et al was claimed to defend pollution attacks efficiently. However, we find that the scheme easily incurs multi-generation pollution attacks, where an adversary may be able to recover the main secret key of the source with high probability during multi-generation transmitting, and the scheme also cannot resist against inter-generation pollution attacks. Using a dynamic source secret key technology that the key can be updated with the change of generation identifier, an improved scheme is then presented, which can counteract these security defects without any efficiency compromise.