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arXiv · 2405.07848

Positional-Unigram Byte Models for Generalized TLS Fingerprinting

Hector A. Valdez·Sean McPherson
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Abstract

We use positional-unigram byte models along with maximum likelihood for generalized TLS fingerprinting and empirically show that it is robust to cipher stunting. Our approach creates a set of positional-unigram byte models from client hello messages. Each positional-unigram byte model is a statistical model of TLS client hello traffic created by a client application or process. To fingerprint a TLS connection, we use its client hello, and compute the likelihood as a function of a statistical model. The statistical model that maximizes the likelihood function is the predicted client application for the given client hello. Our data driven approach does not use side-channel information and can be updated on-the-fly. We experimentally validate our method on an internal dataset and show that it is robust to cipher stunting by tracking an unbiased $f_{1}$ score as we synthetically increase randomization.

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Hector A. Valdez, Sean McPherson. 2024-05-13. Positional-Unigram Byte Models for Generalized TLS Fingerprinting. https://arxiv.org/abs/2405.07848

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