Brink is excited to announce that Martin Zumsande has (re)joined Brink to continue his work on Bitcoin Core including P2P networking, validation, testing, and review! Martin will focus on researching address relay propagation, improving block download reliability, closing a privacy leak in wallet transaction rebroadcast, and expanding validation fuzz testing, in addition to continued code review.

Welcoming back Martin Zumsande

Martin Zumsande has joined Brink to continue his work on Bitcoin Core

Reproducing rare bugs found during fuzz testing is hard because software can run slightly differently every time. Bedrock is a hypervisor that controls that randomness, so given the same inputs a program runs identically on every execution. Niklas outlines an approach and a solution, bedrock, for this problem of determinism. He focuses on the challenge of emulating time and pausing a VM at an exact instruction count, something CPUs aren't designed to do.

Introducing Bedrock: A Deterministic Hypervisor

Bedrock: A general solution to achieving full determinism in software testing by building a deterministic hypervisor to emulate time and trigger vi...

The result is an open source tool, bedrock: an experimental hypervisor purpose-built for deterministic software testing.

GitHub

GitHub - oss-garage/bedrock: Experimental Hypervisor Purpose-Built for Deterministic Software Testing

Experimental Hypervisor Purpose-Built for Deterministic Software Testing - oss-garage/bedrock

Toby Sharp joined Brink engineers to present Hornet, an executable specification for Bitcoin consensus. In his presentation, he discussed: * “The code is the spec” * How Hornet differs from libbitcoinkernel * Properties of a good specification * The 35 semantic rules that define block validity * A declarative C++ implementation of the rules * A custom UTXO database designed for Bitcoin * Approaches to block validation * Ideas of a domain specific language (DSL) for consensus * Differential and adversarial testing * Q&A with the audience

Toby Sharp on Hornet, an executable specification for Bitcoin consensus

Toby Sharp presents Hornet, an executable specification for Bitcoin consensus.

Brink has always funded remote engineers, since our inception. Our London office is there for those who want an in-person space to collaborate, but it's always been optional. In fact, most of the engineers we've funded over the years have worked remotely. The mix shifts over time. Right now it's 5 in office and 4 remote. Wherever you are and whatever lets you do your best work on Bitcoin is what we're here to support.

Two research interns, Dongjia Zhang and Stratos, recently wrapped up their 3 months of work on fuzz testing for Bitcoin Core. Under the guidance of Niklas Gögge, each conducted independent research & experimentation on Fuzzamoto. Dongjia is a Ph.D. researcher specializing in software security and fuzzing, and is the maintainer of LibAFL, a popular fuzzing framework. His extensive background in fuzzing made him well suited to contribute to several of Fuzzamoto’s engineering and testing challenges. Stratos is a vulnerability researcher and approached Bitcoin Core security from a systems and protocol security perspective. 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. Read more on their achievements during the internship:

Fuzz Testing Research Interns: Dongjia Zhang and Stratos

A summary of Dongjia Zhang and Stratos

Thank you Dongjia and Stratos for your contributions!

We published Brink's annual financial and organizational report for the community. Feedback and questions welcome.

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