Cryptography Reference
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choice of cluster size, the system consumes reasonable amount of control cost which
is higher than SN but less than DHT system.
iii)
Under all type of attacks, it showed
the best resilience in terms of coverage and latency. Another interesting observation is
that SN network, even with less network connections, could show better results than
DHT network against the random attack. However its reliability benefit is immediately
cancelled by sophisticated and targeted attackers.
6Analy s
Our evaluation shows that the hybrid network gained the number of reliability benefits
by adding a constant number (two) of SN connections to the DHT network. This re-
sult indicates that the number of connections and the way it connects participants can
seriously impact the reliability of the system. Unfortunately, the number of network
connections is constrained by both system and network resources. Therefore, we want
to explore the design space that can enhance reliability by only improving the way it
connects participants. To that end, we investigate different ways of implementing con-
trol systems by using the same number of connections. More concretely, we extend
DHTs with the fixed number (two) of connections in different ways to observe how
these influence the coverage result. The number of connections is the same one used
from the previous evaluations. Of course, this parameter can have significant impact on
coverage results. However, for all proposals, we want to demonstrate how we can add
connections under the same constraints and maximize the coverage benefits.
To further enhance the system's behavior when attacked, we leverage the benefits of
DHT's internal structure with a modified routing table. This technique, which exploits
finger-table, is implemented for Chord and is also applicable to other DHT systems.
6.1
Chord Connection Types
The Chord maintains two types of logical network connections. One for the
successor
lists
and the other for the
finger table entries
.
- Successor list
maintains the list of neighboring nodes. It is an important param-
eter that influences DHT's reliability and its default size is set to five. Having a
O
(log
n
) size of this connection provably guarantees the stability of the system
which indicates success rate of lookup request.
- Finger table
is a core data structure that implements
O
(log
n
) routing of Chord.
The upper limit of its size is logarithmic to the size of hash space (in the case of
Chord, this is set to 2
160
).
Unlike previous proposals which naıvely added SN connection to DHT connections,
we implement a hybrid network utilizing existing slots of finger tables. SN connections
can be replaced with immediately preceding entries in the finger table. This does not
increase the required state per node or the total number of connections, but this costs
additional hops for lookup activities due to some sub-optimal entries.
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