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MLCerts -- Source Code

Hallucinating Certificates: Differential Testing of TLS Certificate Validation Using Generative Language Models (ICSE 2026)

Talha Paracha, Kyle Posluns, Kevin Borgolte, Martina Lindorfer, David Choffnes

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aux.pdf provides additional supplementary material for the paper.

Certificate Datasets

Raw PEM certificates used in differential testing can be downloaded here.

• 12 synthetic certificate datasets.
• MLCerts 1M dataset.
• Frankencerts 8M dataset.
• Transcert 30K dataset.

Differential Testing Framework

The code is available in /differential-testing/ directory. A Docker image for running the framework is available here.

Language Models

The code, documentation and saved models are available together for download here. A Docker image for CPU-based certificate generation is available here.

Code for Paper Results

Please refer to /paper-code/ directory.

We use IPython Notebooks for producing paper results. The scripts used for different purposes are indexed below:

1. Certificate corpus analysis: Tables 1 and 3
2. Graphs/Graph-DiscrepanciesVSCoverage: Figure 2
3. Graphs/Graph-Matrix: Figure 3
4. Graphs/Graph-Temperature: Figure 4
5. Graphs/Graph-CertCountVSDiscrepanvies: Figure 5
6. Zlint for 00000s + Diversity Comparison Zlint: Figure 6 and 5.3.2 analysis
7. Library checkpointing: Figure 7
8. Discrepancy analysis + Library logs analysis : 5.3.1 analysis

For all notebooks, the output information should be intact to help avoid re-running code.

BibTeX

Please cite our paper if you rely on the artifacts for your work.

@inproceedings{icse2026-hallucinating-certificates,
  title     = {{Hallucinating Certificates: Differential Testing of TLS Certificate Validation Using Generative Language Models}},
  author    = {Paracha, Talha and Posluns, Kyle and Borgolte, Kevin and Lindorfer, Martina and Choffnes, David},
  booktitle = {Proceedings of the 48th IEEE/ACM International Conference on Software Engineering (ICSE)},
  date      = {2026-04},
  edition   = {48},
  editor    = {Mezini, Mira and Zimmermann, Thomas},
  location  = {Rio de Janeiro, Brazil},
  publisher = {Association for Computing Machinery (ACM)/Institute of Electrical and Electronics Engineers (IEEE)}
}