Protocol Core Engineer

Core Protocol EngineerPosition: Senior Engineer Location: Miami, FL strongly preferred Project: Char NetworkAbout Char NetworkChar Network is a proof-of-stake application coordination protocol built on Bitcoin. By anchoring data into Bitcoin through cryptographic proofs and economic guarantees, Char powers the next generation of Bitcoin layer twos.We’re a small, sharp, and adventurous team led by Bitcoin developer Jeremy Rubin, pushing the limits of what Bitcoin can be. Our work blends deep protocol expertise with a hacker’s creativity to unlock new capabilities for Bitcoin at scale.We keep things collaborative, fast-moving, and fun—where every contribution counts and every voice matters. Joining Char Network means working at the frontier of Bitcoin R&D and infrastructure, where the code you write and the algorithms you create will shape the future of the ecosystem.About the RoleYou’ll be building the systems that make Char Network run: consensus node implementation, Bitcoin transaction construction, proof generation and verification, and the testing infrastructure that keeps it all reliable. This is a hands-on engineering role where you’re writing the core software that anchors a proof-of-stake protocol into Bitcoin.You’ll work closely with our research team to translate new consensus and cryptography designs into hardened, production-grade code. You should be comfortable moving fast on early prototypes and then going deep on optimization and correctness.What You’ll DoDesign and implement domain-specific consensus mechanisms: ballot advancement, leader election, and fork-free attestation coordinationEngineer Bitcoin integration: stake bond design (taproot outputs, timelock slashing), cryptographic verification (BLS signatures, hash trees), and proof validation pipelinesBuild P2P networking and RPC/CLI interfaces for CHAR protocol operations: ballot propagation, leader advertisements, state inspection, and operator commandsDesign storage and indexing systems for protocol state: bond tracking, ballot history, and attestation persistence with reorg resilienceDevelop comprehensive testing infrastructure: multi-node simulation, edge case coverage, fuzzing, and DoS scenario validation; conduct rigorous code reviews across the entire stackWhat We’re Looking ForMust-HavesStrong systems programming skills in C++ with a focus on correctness, performance, and memory safetyExperience with low-level programming: memory management, concurrency primitives, performance profilingComfort working across the stack including cryptographic primitives, networking, storage, and build systemsStrong problem-solving instincts and the ability to debug complex, multi-layered systemsCollaborative mindset; you give and receive code review feedback constructivelyNice-to-HavesExperience building Bitcoin applications or familiarity with Bitcoin Core codebasePractical experience with cryptographic implementations (hash functions, signature schemes, zero-knowledge proofs, BLS signatures)Familiarity with distributed consensus: ballot voting, leader election, fork-free protocols, Byzantine fault toleranceExperience designing and implementing P2P protocols for custom messages and state propagationContributions to open-source projects in the Bitcoin or broader crypto ecosystemUnderstanding of timelock-based economic mechanisms and slashing conditionsReading MaterialsChar Network — MIT Bitcoin Expo Presentation (2026)BitVM Whitepaper + BitVM2 WhitepaperBitVM High-Level ExplainerPurify Library