
supporting it. Dictionaries may turn into disadvantage,
if they are hard to maintain and update. Currently the
process of the creation of data set collection was manual,
but there are ongoing researches, attempting to automatize
it in the future. [30].
Classification tools usually require to be trained on a
particular data set consisting of benign traffic, which must
be updated regularly to ensure novelty data. Especially
hard to maintain and update is the collection of malware
samples [2c03].
5. Conclusion
Encryption of data is crucial when aiming to protect
the privacy of users. In modern networks, the TLS proto-
col is the current encryption standard for data transferred
over the Internet. Although it is used to mask the plain text
information from the application layer, TLS also provides
a set of unique observable parameters that allow many
conclusions to be made about both the client and the server
[1].
In this paper we have reviewed the three most widely
spread/diverse techniques used for TLS fingerprinting,
starting with the simplest one – Network-based HTTPS
Client identification – essentially divided into two ap-
proaches, which are both based on the extraction of the the
most varied components from the TLS session initializa-
tion messages and writing them down in a database. The
second one being the JA3/JA3S that is partially based on
the Network-based identification as it upgrades it through
memory optimization, hashing the values into 32-character
unique fingerprint, making it quicker for malware software
to be recognized. The last and most complicated method
is the creation of a fingerprint using homogeneous Markov
chains (either first or second order) so as to simulate
the time-varying message sequence that occurs during the
TLS session initialization. Vital characteristic trait of this
method is that conducted on the server side and focuses
mainly on detecting abnormal TLS sessions and improv-
ing discrimination practices. All of these techniques can
identify clients with high accuracy while sustaining their
privacy. A comparison based on the statistical accuracy
of these techniques is hard to derive, because experiments
with each one of them has been done individually, over
different amounts of time, using different traffic samples.
In the future it would be interesting to conduct an
experiment to test how these three techniques would per-
form under the same set of conditions (e.g. time window,
network and servers).
Overall, TLS fingerprinting is a subsection of passive
client identification and traffic. There are other methods
for client fingerprinting, that may partially incorporate
the TLS technology (for example OS fingerprinting [31],
web browser fingerprinting, website fingerprinting, signal
fingerprinting, cookies [32]) that are efficient as well.
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Seminar IITM WS 19/20,
Network Architectures and Services, April 2020 19 doi: 10.2313/NET-2020-04-1_04