Cooperative Security for Network Coding File Distribution
Abstract: Peer-to-peer content distribution networks can suffer from
malicious participants that corrupt content. Current systems verify
blocks with traditional cryptographic signatures and hashes. However,
these techniques do not apply well to more elegant schemes that use
network coding techniques for efficient content distribution.
Architectures that use network coding are prone to jamming attacks
where the introduction of a few corrupted blocks can quickly result in a
large number of bad blocks propagating through the system. Identifying
such bogus blocks is difficult and requires the use of homomorphic
hashing functions, which are computationally expensive.
This paper presents a practical security scheme for network coding
that reduces the cost of verifying blocks on-the-fly while efficiently pre-
venting the propagation of malicious blocks. In our scheme, users not
only cooperate to distribute the content, but (well-behaved) users also
cooperate to protect themselves against malicious users by informing
affected nodes when a malicious block is found. We analyze and study
such cooperative security scheme and introduce elegant techniques to
prevent DoS attacks. We show that the loss in the efficiency caused by
the attackers is limited to the effort the attackers put to corrupt the
communication, which is a natural lower bound in the damage of the
system. We also show experimentally that checking as low as 1-5% of
the received blocks is enough to guarantee low corruption rates.
