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Sixteenth Wave of Bitcoin Grants

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    OpenSats
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  • avatar
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    Arvin
    Twitter
    @arvin

OpenSats is pleased to announce the sixteenth wave of grants from our General Fund, supporting seventeen open-source projects across the Bitcoin ecosystem. This round includes ten first-time project grants and seven grant renewals.

The projects in this wave strengthen Bitcoin's ecosystem at several layers. They improve script tooling and developer libraries, apply formal methods to critical cryptographic code, and advance ecash infrastructure that mint operators can run themselves. Additional grants support self-custodial wallets, DIY signing hardware and installer software, alternative node and mining software, and education programs that help new developers become contributors.

The first-time project grants highlighted in this wave are:

Grant renewals have been awarded to:

These grants are made possible by donations to our General Fund. To help sustain free and open-source Bitcoin development, please consider setting up a recurring donation.

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Let's take a closer look at the projects in this wave and how they will make an impact on the Bitcoin ecosystem.

Advancing Formal Verification for Bitcoin Cryptography

Advancing Formal Verification for Bitcoin Cryptography is a research effort by developer remix7531 on the cryptographic building blocks that secure Bitcoin software. The project focuses on RustCrypto's sha2 and k256 crates and on multi-scalar multiplication for the secp256k1 curve, a key operation for batch signature verification in Bitcoin. Remix7531 applies proof assistants and formal methods to construct machine-checked proofs for critical cryptographic routines and to connect them to Rust and C implementations.

This grant will support formal verification on these RustCrypto crates and on multi-scalar multiplication for the secp256k1 curve. The project will use the HAX toolchain with F* to prove panic freedom and functional correctness and to rule out overflows, failed bounds checks and non-terminating loops. It will also develop precise specifications and proofs for multi-scalar multiplication and will compare proof assistants for verifying performance-critical C implementations. The resulting code, proofs, and technical reports will be released under a free software license and will serve as a blueprint for future formal verification of Bitcoin cryptographic libraries.

Repositories: /remix7531
License: MIT

BitcoinerLAB and RewindBitcoin

BitcoinerLAB is a TypeScript toolkit by developer Landabaso for building Bitcoin applications with descriptors and Miniscript. It provides modules for address and transaction construction, signers and blockchain backends, and it integrates with bitcoinjs-lib for use in existing JavaScript codebases. Thousands of public repositories depend on BitcoinerLAB, including Ledger APIs, Bitcoin Keeper, LN Markets, and RewindBitcoin.

RewindBitcoin is another project by Landabaso. It is a self-custody mobile wallet for iOS and Android that applies vault-style spending controls. It uses timelocks, pre-signed transactions, and an emergency spending path to protect funds in situations of theft or coercion.

This grant will support BitcoinerLAB and RewindBitcoin. For BitcoinerLAB, work will include Taproot Miniscript support in TypeScript, broader hardware wallet integration through a general signer API, and a cleared backlog of features such as MuSig-style multisig, CPFP, and RBF in the coin selector, plus new documentation and use-case guides. Planned work on RewindBitcoin will explore Pay-to-Anchor and TRUC-based rescue flows, add hardware wallet support on top of that design, and improve coin control, labeling, fee management, and overall UX. These projects aim to create stronger Miniscript foundations for TypeScript developers and a practical vault wallet for people facing real risks of theft or coercion of their Bitcoin.

Repositories: /bitcoinerlab; /rewindbitcoin
Licenses: MIT; GPL-3.0

BTCaaron and Mastering Taproot

The btcaaron project is a lightweight Python toolkit by developer aaron-recompile for Bitcoin Layer 1 development with a focus on Taproot. It runs on testnet and supports Legacy, SegWit, and Taproot address types, UTXO scanning, transaction construction, signing, and broadcasting for testnet flows. It also exposes a Taproot-native API for building script trees, key-path and script-path spends, and automatic witness construction for common spend paths.

Mastering Taproot is Aaron Zhang's open-access developer guide to Taproot, with full Python code samples,testnet transactions, and step-by-step stack execution, published in English and Chinese as a reproducible online book. The text uses clear examples, control block diagrams, and verifiable transaction IDs so readers can inspect and replay every construction.

This grant will support btcaaron and Mastering Taproot. Planned work for btcaaron includes a refactored core structure, new helpers for Taproot script-path spending, PSBT v2 support, multi-leaf Taproot construction utilities and visualization and simulation features for Taproot scripts, along with a 1.0 release for testnet and regtest workflows. Planned work for Mastering Taproot includes finalizing the English manuscript, expanding runnable examples, releasing Chinese translations of key chapters, and publishing tutorial videos, walkthroughs, and workshop materials for Bitcoin scripting education. The goal is a cohesive toolkit and curriculum that lowers the barrier for new Bitcoin developers, especially in Chinese-speaking communities, and accelerates practical Taproot experimentation.

Repositories: /btcaaron; /mastering-taproot
Licenses: MIT; CC BY-SA 4.0

Cashu Dev Kit (CDK)

Although we have supported the CDK project in the past, this additional grant supports developer Asmo for his work on CDK operability across cloud environments. Cashu Dev Kit is the core Rust toolkit for operating Cashu mints and services. It supports Postgres for storage, Prometheus for metrics, and provides Docker images for common environments, including ARM64. Asmo triages bugs, reviews pull requests, and adds features for operators and integrators. His work includes the Prometheus exporter and Grafana dashboard, improvements to Postgres and FFI support, and the Blink payment processor backend.

With this grant, Asmo will turn CDK into a cloud-native infrastructure for Cashu mints. The roadmap expands Prometheus metrics to cover database and payment activity and feeds them into Orchard dashboards for mint operators. He plans to build a Cashu Kubernetes Controller that manages CDK mints and Orchard on Kubernetes clusters and handles rolling upgrades, configuration secrets, health probes, backups, and restores. Logging will move to structured JSON formats, and configuration will be simplified and documented so deployments stay predictable at different scales. Build pipelines will migrate to self-hosted GitHub runners, and CDK will publish several image profiles for minimal, base, standalone, and cloud deployments. In parallel, Asmo will prototype secure deployments on Amazon Nitro Enclaves and extend gRPC-based payment backends such as cdk-blink-payment-processor to support BOLT12, on-chain payments, and additional providers including Stripe, Strike, and LNbits.

Repository: cashubtc/cdk
License: MIT

Cashu TS and Coco

Cashu TS is a TypeScript library for building Cashu wallets and applications. Maintained by returning grantee Egge, lead developer of npub.cash, cashu-ts wraps the Cashu protocol and NUTs into a reusable wallet toolkit so developers can connect to mints, mint and melt ecash, and manage tokens without reimplementing low-level logic. The library is widely used in the Cashu ecosystem and powers web, mobile, and backend integrations in projects ranging from wallets to merchant tools.

Coco builds on cashu-ts and adds networking, storage, key management, and a unified API so developers can embed a full Cashu wallet in browsers, Node.js, and React Native with minimal connective code.

With this grant, Egge will keep cashu-ts aligned with new Cashu NUTs and protocol changes and complete its ongoing API migration while maintaining stability for existing dependents. He plans to refine documentation and examples so application teams can adopt new features without friction. He will also push Coco toward its first stable release and add missing protocol features such as automatic key handling for locked and BOLT12 mint quotes, tools for managing balances across multiple mints, multi-nut payments that combine funds from several mints for one invoice, and payment request flows with nostr integration. The goal is a pair of libraries that keep TypeScript Cashu support robust and give developers a toolkit for integrating ecash into new applications.

Repositories: /cashu-ts; /coco
License: MIT

Krux-Installer

We have supported the krux-installer project in the past, and this additional support goes to developer joazinhom for his work on the installer and its platform reach. Krux is open-source firmware that turns inexpensive Kendryte K210 devices into air-gapped Bitcoin signing devices, and Krux-installer is the desktop application that flashes and upgrades this firmware on supported hardware. The installer replaces complicated command-line tools with a guided GUI so non-technical users can install and update Krux from official releases on their own devices.

With this grant, joazinhom will work on modernizing Krux-installer and expanding its platform support by refactoring the codebase, migrating dependency management from Poetry to UV, and adding a device registry system that reduces duplication when onboarding new devices. He will move the build system to the BeeWare/Briefcase framework to produce native installers for Android and Flatpak-based desktops and to create a sustainable pattern for future platforms. In the final phase, he will focus on testing and stabilizing these builds, fixing touch and installation issues, and improving overall reliability for users flashing and upgrading Krux devices.

Repository: /krux-installer
License: MIT

Libbitcoin

Libbitcoin is a C++ Bitcoin development toolkit and an alternative full node implementation. It provides a modular node, server, and explorer stack together with cross-platform libraries for building Bitcoin applications. The project began in 2011 and produced the first independently implemented Bitcoin full node separate from Bitcoin Core, and it remains under active maintenance with work toward a version 4 release that emphasizes faster initial block download and better scaling with modern hardware.

This grant will support work on libbitcoin v4 by developer pmienk. Planned work targets an early preview of the v4 node, followed by a full release of the node, explorer, and server components. The focus includes further optimization of initial block download, performance scaling across available CPU, disk, and network resources, integration and testing of the consolidated stack, and improvements to documentation for operators and developers. The goal is a well-engineered Bitcoin node, server, and explorer that provides an independent implementation of the protocol and a practical toolkit for downstream applications.

Repositories: /libbitcoin
License: AGPL-3.0

Noah

Noah is a self-custodial mobile wallet for Ark, a Layer 2 protocol, developed by returning grantee Hampus Sjöberg, creator of Blixt Wallet. Noah runs on Android and iOS and uses Ark's virtual transaction outputs (VTXOs), so users see a single balance that can send and receive over Lightning and on-chain. The wallet connects to Second's Ark client Bark and removes channel setup, liquidity management, and backup complexity while keeping users in control of their keys. A working alpha already supports sending and receiving payments and builds on years of experience operating Blixt as a non-custodial Lightning wallet.

With this grant, Hampus will work on reliable Ark round syncing using silent push notifications, Lightning Address and future BIP-353 support, expanded LNURL features, and a seed-based encrypted backup system. He will also add receive flows that let the app accept payments while it is offline. The roadmap adds auxiliary Lightning and nostr integrations such as the LNURL protocol suite, WebLN, Nostr Wallet Connect, payments via nostr profiles, and Tor support for privacy. Alongside Noah, Blixt will shift toward a power-user wallet with planned features including BOLT12 support tied to the upcoming lnd release, offline receive, faster chain sync, desktop builds for Windows and Linux, Lightning/on-chain swaps, LSP-spec support, and interface improvements.

Repository: /noah
License: MIT

Rust-Bitcoin

Through this grant, we continue our support for rust-bitcoin projects by providing additional funding to developer mpbagot for his work on the library, which provides Rust types and utilities for serializing, parsing, and executing Bitcoin protocol messages, blocks, transactions, scripts, keys, addresses, and PSBTs in Rust applications. The library sits at the center of the rust-bitcoin organization together with crates such as rust-secp256k1, bitcoin_hashes, rust-miniscript, and client libraries for Bitcoin Core, and it underpins projects like Bitcoin Dev Kit, Lightning Dev Kit, electrs and Fedimint.

This grant will support work on upcoming releases of the main bitcoin crate and related primitives, bug fixes, expanded test coverage, documentation improvements, and refactoring across the crate set. Bagot will continue his existing cleanup patches and will take on larger tasks aimed at stable 1.0 releases of key crates in the ecosystem. The goal is a well-tested, well-documented, and CC0-licensed Rust Bitcoin stack with stable APIs for downstream projects.

Repository: /rust-bitcoin
License: CC0 1.0

Stratum V2

Our support for Stratum V2 continues with a new grant to developer Lucas Balieiro for his work on the Stratum V2 Reference Implementation (SRI), focusing on stability, testing, and developer tooling. SRI is the Rust reference implementation of the Stratum V2 mining protocol and provides core libraries and pool and miner applications for encrypted, decentralized pooled mining. It powers roles such as pool servers, miners, and job declaration clients and serves as the main open-source codebase for adopters of Stratum V2 in production mining setups.

With this grant, Balieiro will improve SRI's testing infrastructure and adopter experience. Planned work includes expanding the continuous testing tool for long-running cross-implementation sessions, raising low-level crate test coverage from roughly 25% toward 40%, and updating documentation alongside new tests. He will build a unified command-line interface for launching SRI applications, add Docker support and binary releases for easier deployment, and streamline CI workflows to integrate the new testing tools. The roadmap also covers compatibility testing with other Stratum V2 stacks and community work, such as mentoring contributors and running educational sessions with the Brazilian Bitcoin community.

Repository: /stratum
License: Apache-2.0/MIT

The projects in this wave share a focus on practical Bitcoin infrastructure that people can run and verify themselves. They move core libraries, wallet tooling, ecash systems, and mining software toward greater security and usability for both developers and end users. They strengthen self-custody, improve reliability for operators, and expand pathways for new contributors.

As with all OpenSats grants, funding decisions follow a mission-aligned review process grounded in clear criteria. Our ability to fund this work depends on donations to our General Fund. If you would like to help sustain these projects and future grants, please consider setting up a recurring donation.

Give Monthly 🧡

If you are building free and open-source Bitcoin software, we encourage you to apply for funding.

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