A distributed decision log for meetings within a consortium of organizations
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Typ
Examensarbete för masterexamen
Program
Publicerad
2021
Författare
Jonsson, Niklas
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
When conducting meetings within a consortium of organizations, a method of recording
key aspects like participation and decisions so that they can be agreed upon by
all parties is needed. A decision log based on a distributed ledger; a data store
that is shared on equal terms between the organizations, would remove the need to
trust a central authority, and if the data structure of the ledger is a cryptographically
chained log, the entries are immutable and secure against tampering. Using
a Byzantine fault tolerant (BFT) consensus algorithm when reaching agreement on
the state of the data store would further increase the security of the system by
making it tolerant against malicious behavior from some of the organizations.
The introduction of smart contracts has broadened the field of use cases where
distributed ledgers are considered. However, poor performance compared to other
systems due to the high complexity of their consensus algorithms is often a limiting
factor. While providing the desired functionality, the performance of a system such
as this has to be sufficient to be usable; users have to see the response of their actions
in near real-time and the meeting cannot be significantly delayed.
A prototype system based on these methods was designed and developed, and
evaluated in terms of usability. Two metrics were defined to quantify the usability,
response time and overhead. Response time was defined as the delay between a user
action and its response and overhead was defined as the time added to a meeting by
the system when recording the outcome of a decision. The results were measured
at different scales in terms of meeting participants, network delay and number of
nodes participating in the consensus method.
It was found that the performance impact of using a distributed ledger with
a BFT consensus algorithm is considerable. The response time remained at sufficiently
low levels, between 1.4 and 3.4 seconds. However, due to the high message
complexity of BFT consensus methods, the overhead of the system was too high
for the system to be considered practical; between 12 and 110 seconds for a single
decision. A high number of users especially affected the overhead negatively, but
the number of participating organizations and the amount of network delay also had
a significant effect.
In conclusion, distributed ledgers in combination with Byzantine fault tolerance
provides a high level of trust and security to a system, but performance is a big
issue that limits the reasonable uses of the technologies. If a system is designed
with these technologies, special care has to be taken to keep the rate of events low
so that the performance remains sufficient.
Beskrivning
Ämne/nyckelord
distributed systems , distributed consensus , distributed ledger technology , blockchain , Byzantine fault tolerance