  Dealing with pollution attacks in inter-session network coding is challenging
due to the fact that sources, in addition to intermediate nodes, can be
malicious. In this work, we precisely define corrupted packets in inter-session
pollution based on the commitment of the source packets. We then propose three
detection schemes: one hash-based and two MAC-based schemes: InterMacCPK and
SpaceMacPM. InterMacCPK is the first multi-source homomorphic MAC scheme that
supports multiple keys. Both MAC schemes can replace traditional MACs, e.g.,
HMAC, in networks that employ inter-session coding. All three schemes provide
in-network detection, are collusion-resistant, and have very low online
bandwidth and computation overhead.
