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Fifth Wave of Bitcoin Grants


As we enter the 5th Bitcoin epoch, OpenSats is proud to announce our 5th wave of Bitcoin grants. While Bitcoin continues its journey of increasingly embedding itself into global institutional finance and public markets, we must not forget that behind these notable milestones are hardworking, passionate individuals who dedicate their time and energy to writing and maintaining free and open-source Bitcoin software.

Our goal is to provide sustainable funding for FOSS contributors, especially those who make Bitcoin flourish. Over the last couple of weeks, our board has selected ten more projects for funding.

In alphabetical order, they are:

These grants are sourced from our General Fund, which is funded by generous donors like you. If you would like to support free and open-source projects that help Bitcoin flourish, consider donating to the fund:

We are incredibly grateful for all donations—large and small—and are happy to have received significant donations from The Reynolds Foundation and #startsmall recently, which helped enable these grants.

Without further ado, let us take a closer look at the projects to understand what they are about and how they align with our mission:

Core Lightning Bookkeeper Dashboard

The Core Lightning Bookkeeper Dashboard provides a Graphical User Interface to the Core Lightning (CLN) back-end. Core Lightning is one of the four major Lightning implementations alongside Eclair, Lightning Development Kit (LDK), and Lightning Network Daemon (LND).

The dashboard is inspired by Umbrel’s Lightning app, which in turn was built upon work done by Casa for their Lightning node implementation. This is the power of FOSS on full display: being able to build upon previous work to the benefit of all.

This grant is to support the addition of three new visual elements to the bookkeeper:

  • A balance sheet tracker to show the current and historical balance of sats on the node each day.
  • The "sats flow" to show the changes in debits and credits over time
  • A volume chord schematic to show the flow of sats routed between nodes.

In combination, these features will improve accessibility to the underlying data CLN already captures.

Repository: ElementsProject/cln-application
License: MIT


Cove is a new single-sig mobile wallet optimized for use with hardware signing devices. Cove leverages BDK with the core of the app built in Rust and an interface built with SwiftUI (for iOS) and Jetpack Compose (for Android). The design objective is to make this a first choice for new bitcoiners, making it easy as they move to hardware signing devices—and subsequently to watch-only wallets.

This grant will enable the build of the core wallet along with support for Partially Signed Bitcoin Transactions (PSBTs) via Near Field Communications (NFC), Quick Response codes (QR), and virtual drives for offline signing. In the future, Cove will support coin control, passphrase use, multiple accounts, decoy wallets, and connecting to your own node.

Repository: bitcoinppl/cove
License: MIT

Fedimint On-Chain Wallet

Fedimint is an open-source federated Chaumian eCash mint project used by several eCash projects, including Fedi and Mutiny Wallet. Chaumian eCash provides significant privacy benefits to mint users, and at its core uses the groundbreaking work of cryptographer David Chaum from 1982. Fedimints require no changes to either the Bitcoin base layer or the Lightning protocol.

This grant supports work to improve the liquidity and efficiency of exiting from mints via the on-chain wallet. Fedimint traditionally uses the Lightning Network as the instant settlement and connectivity fabric between mints, but exiting directly to Bitcoin's base layer was always part of Fedimint's design. Work on the on-chain wallet will focus on optimizing these base-layer transactions under load.

Repository: fedimint/fedimint
License: MIT


Krux is open-source firmware that enables anyone to build their own Bitcoin signing device via off-the-shelf parts. It runs on Kendryte K210 devices such as the Maix Amigo or the M5StickV (among others), converting them into air-gapped devices that can sign transactions for multisignature and single-signature wallets.

This grant supports the effort to expand firmware functionality and the range of supported devices, including PCs and Android mobile devices. New features will include the introduction of Krux Apps to enable games, additional OpSec features, and the ability to use the signing device for Nostr.

Repository: selfcustody/krux
License: Apache2 & MIT

Krux Installer

Whilst Krux is an open-source firmware that allows anyone to build their own signing device for Bitcoin transactions, krux-installer is the desktop application that allows anyone to install the Krux firmware in a safe, easy, and transparent way. This makes the use of Krux more accessible and consequently helps adoption and use; GrapheneOS’s deployment of a web-based installer for their OS onto hardware similarly saw upticks in adoption and use for the same reason.

This grant will enable the project to refactor and align the technology between krux and the krux-installer, improving supportability and reducing technical footprint. Additionally, this grant will allow developers to focus on macOS deployment and implement a "Wipe the device" feature to enhance security.

Repository: selfcustody/krux-installer
License: MIT

Lightning Network Protocol Test Framework

The Lightning Network protocol test framework provides a common and reusable framework for easier testing of proposed protocol changes. This framework allows developers to test the impact on other implementations as part of the verification and validation process. It is part of the aptly named Lightning Network Interoperability Initiative, which—you guessed it—aims to improve the interoperability between various Lightning Network implementations.

This grant will be used to turn the test framework into a library, making re-use by each group working on the Lightning Network simpler, and can be used to build and expand a base set of tests that are shared. In this way, each group can contribute to a common test pool for the protocol, including those who have implementation-specific features (such as Pool or AMP).

Repository: rustyrussell/lnprototest
License: MIT


Macadamia is a native iOS wallet written in Swift and SwiftUI for the Cashu Chaumian eCash protocol. The wallet aims to make privacy-preserving eCash use simple, smooth, and stable. Macadamia includes the ability to send eCash on Nostr. It is currently in early-stage beta and is available on Testflight.

This grant supports the separation of wallet and Cashu logic, separating the latter into a stand-alone Swift library with support for mandatory NUTS, and (initially) NUT-07, NUT-09, and NUT-13.

Additional support for more complex Cashu capabilities and better support for mints—including multi-mint multi-path payments—is on the roadmap for future releases.

Repository: zeugmaster/macadamia
License: MIT

Tor Support for BDK & Fedimint

The Bitcoin Development Kit (BDK) provides a library of Bitcoin wallet capabilities for developers to build cross-platform Bitcoin wallets without needing to worry about Bitcoin internals. Fedimint is an open-source Chaumian eCash framework project that leverages BDK, and like BDK is also written in Rust. Fedimint should not be conflated with any commercial efforts building on top of the open-source protocol, such as Fedi.

This grant effort will focus on delivering Tor support for Fedimint clients and adding new gateways and PayJoin support. For BDK, this grant effort is focused on Tor support for the rust-esplora-client, upgrading rust-bitcoin, and building support for pruned nodes.

Both Fedimint and BDK are increasingly being leveraged by other projects in the wider Bitcoin ecosystem, such as BitKey, Mutiny Wallet, and LDK. Consequently, it is important that these building blocks provide a strong level of privacy and security.

Repositories: bitcoindevkit/bdk & fedimint/fedimint
Licenses: MIT/Apache2 & MIT


Utreexo utilizes Merkle trees to provide an alternate structure for access to Bitcoin data, enabling compact state nodes, parallelization of the Initial Block Download (IBD), and thereby wider distribution of functional Bitcoin nodes. This opens the door to browser-based and smaller low-power devices to become Bitcoin nodes—including mobile devices!

This grant supports the activities to complete the P2P tx messaging implementation, write up the four BIPs required for utreexo, and commence building the bridge node implementation within Bitcoin Core. Subsequent work on optimizing performance for IBD, increasing efficiency in the accumulator implementation, and improving library support are to follow.

Repository: utreexo/utreexo
License: MIT

Validating Lightning Signer

Validating Lightning Signer (VLS) is an open-source project with the explicit goal to improve the security of the Lightning Network, by separating "hot" bitcoin keys from operational Lightning nodes. VLS works by storing private keys in a specialized signing device which adds an additional layer of security. Especially for businesses and enterprises this additional security provides important safeguards currently not accessible.

This grant supports the work for VLS focused on support for low-resource signers, tuning for embedded processors, fine-tuning for latency and memory use, and dockerization. Subsequent focus then moves to operation on hardened servers, and validated support for high volume lightning use, i.e. thousands of channels and millions of payments. Future work extends support to LND beyond the initial Core Lightning and LDK implementations, and then to support for Splicing and multi-sig lightning key management.

Repository: lightning-signer/validating-lightning-signer
License: Apache2

This 5th wave of grants to Bitcoin projects follows our earlier announcement in February this year, and last year's announcements in December, August, and July. For more details on the types of projects and people we support, we encourage you to have a look at our grants and reports. If you are a developer working on a project that is aligned with our mission, don't hesitate to apply for funding.