Posted on 4 May 2023

Brink is proud to announce a developer grant for Fabian Jahr. He has joined Brink as a remote grantee to continue his work as a Bitcoin Core developer.

Update: Listen to our discussion with Fabian about his plans on our Twitter Space

About Fabian

Fabian writes of his Bitcoin experience and goals:

Picture of Fabian Jahr

I first contributed to Bitcoin Core in 2019 while participating in the Chaincode Summer Residency. In the preceding year, I was primarily fascinated by the new possibilities enabled by the Lightning Network and was actively involved in some small open-source projects, with a focus on the application layer. Collaborating directly with Bitcoin Core contributors at Chaincode showed me that I could make valuable contributions on the base layer as well. My most significant project to date has been the coinstatsindex, an index in Bitcoin Core that tracks the overall coin supply, a hash of the UTXO set, and other crucial metrics.

I have been enthusiastic about the possibilities that BIP340 Schnorr signatures enable for Bitcoin ever since I learned about them. While recently much attention has been directed towards covenants and related proposals, Schnorr-related innovations can also have a significant impact in making protocols more efficient. I plan to support and extend existing research by implementing batch validation as part of block validation in Bitcoin Core and outlining different paths through which Cross Input Signature Aggregation (CISA) could be integrated at the protocol level and the positive impacts this could have on layer 2 systems as well.

I will continue contributing to Bitcoin Core not only through code but also, and more importantly, through reviews. Slow reviews and a shortage of reviewers are the most significant challenge in Bitcoin Core development. Particularly complex projects necessitate days or even weeks of focused effort to provide competent reviews of concepts and code. This level of dedication is often only achievable for grant recipients, so I consider it my duty to allocate a substantial portion of my time to reviewing, with a primary emphasis on complex projects.

The ASMap feature in Bitcoin Core has already made significant progress, but I also plan to support its adoption by finalizing the process of distributing ASMap mappings with Bitcoin Core releases. This will enable the feature to be used as a default for peer bucketing in Bitcoin Core in the future.

I will also continue to organize and host the monthly Bitcoin Socratic Seminar in Berlin.

A grant from OkCoin allowed me to work full-time on Bitcoin Core during the first half of 2020; otherwise, my contributions were limited to part-time efforts during nights and weekends. I am thrilled to return to working on Bitcoin full-time, collaborate more closely with others at Brink, and be a much more productive contributor as a result.


About Brink

Brink is a Bitcoin research and development centre, founded in 2020 to support independent open source protocol developers and mentor new contributors. If you or your organization is interested in supporting open source Bitcoin development, feel free to email us,

Developers interested in the grant program can apply now.

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