Earlier this year, Brink awarded grants to Dongjia Zhang and Stratos to support their work on fuzz testing research for Bitcoin Core. Under the guidance of experienced contributor Niklas Gögge, each conducted independent research and experimentation on Fuzzamoto, a snapshot fuzzing tool to test complex and previously difficult-to-test parts of Bitcoin full nodes.
Dongjia Zhang
Dongjia is a Ph.D. researcher specializing in software security and fuzzing, and is the maintainer of LibAFL, a popular fuzzing framework written in Rust. His extensive background in fuzzing research made him well suited to contribute to several of Fuzzamoto’s engineering and testing challenges.
During his research internship, Dongjia had over 40 pull requests merged. His work included:
- Extending Fuzzamoto’s intermediate representation (IR) to support additional Bitcoin P2P protocols, including compact filter messages (BIP158) and bloom filter messages (BIP37).
- Scaling coverage measurement to utilize multiple cores, drastically reducing the time required for coverage analysis.
- Developing a hypervisor feedback mechanism in Fuzzamoto to deliver messages from the underlying hypervisor, giving fuzzers better guidance.
- Prototyping bug benchmarks to help evaluate Fuzzamoto’s effectiveness at identifying real bugs.
- Adding new oracles to detect additional categories of logic bugs.
- Improving CI pipelines and applying lints to support long-term code maintenance.
- Contributing improvements to LibAFL, the underlying fuzzing library that Fuzzamoto depends on.
Dongjia reflected on his experience at Brink:
“My internship at Brink was a perfect opportunity for me to apply my expertise in fuzzing to a real-world scenario. I focused on improving fuzzamoto, which utilizes state-of-the-art snapshot fuzzing technique to fuzz complex and previously un-fuzzable parts of Bitcoin clients. Contributing to the security of bitcoind, which impacts a lot of people, is fulfilling, but more importantly, my experience at Brink was very enjoyable.”
Stratos
Stratos is a vulnerability researcher and approached Bitcoin Core security from a systems and protocol security perspective:
“Coming from a technical background, I feel that someone like me is far more likely to be convinced of the revolutionary tsunami that is Bitcoin, because source code does not lie.”
During his research internship, Stratos contributed to Fuzzamoto by:
- Extending Fuzzamoto’s IR to support additional Bitcoin Core protocol primitives, including addrv2 relay and initial taproot support.
- Creating initial benchmarking work for Fuzzamoto, taking the first concrete steps toward measuring fuzzing effectiveness.
- Adding libbitcoin support, expanding Fuzzamoto’s target reach beyond Bitcoin Core, with that work ongoing.
Stratos also described what the experience showed him about Bitcoin development:
“Although technical curiosity initially drew me to this internship, what impressed me most (and what left me very optimistic about the future) was the amount of energy and resources being devoted behind the scenes to Bitcoin’s present and future. That experience gave me a deep appreciation and respect for the open-source community.”
He expressed appreciation for Niklas Gögge’s technical guidance throughout the project:
“Niklas was an incredible help throughout that period, always available to answer any question I had. It was obvious that he cared deeply about every detail of fuzzamoto, from how a feature should be implemented incrementally to where and how it should be integrated.”
Thank You
Both engineers made meaningful contributions to Fuzzamoto. Their work extended protocol support, improved benchmarking infrastructure, scaled coverage analysis, and broadened target coverage for the testing platform.
We thank Dongjia and Stratos for their contributions and wish them well in their continued work in security research and Bitcoin development.
About Brink
Brink is a Bitcoin research and development centre, founded in 2020 to support independent open source protocol developers and mentor new contributors. Find out more about our grants and fellowship programs, and how to support us.
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