--- title: 'Protocol Core Engineer at Char Network' canonical: 'https://feeny.ai/job/protocol-core-engineer-char-network-miami-florida-mxjnvtancrhh' type: 'job' last_seen: '2026-09-11' --- # Protocol Core Engineer at Char Network - **Company:** Char Network - **Location:** Miami Florida, United States - **Posted:** 2026-04-10 - **Last confirmed live:** 2026-09-11 - **Apply:** https://job-boards.greenhouse.io/charnetwork/jobs/4210189009 ## Job description Core Protocol Engineer Position: Senior Engineer  ·  Location: Miami, FL strongly preferred  ·  Project: Char Network ## About Char Network Char 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](https://rubin.io/), 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 Role You’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 Do - Design and implement domain-specific consensus mechanisms: ballot advancement, leader election, and fork-free attestation coordination - Engineer Bitcoin integration: stake bond design (taproot outputs, timelock slashing), cryptographic verification (BLS signatures, hash trees), and proof validation pipelines - Build P2P networking and RPC/CLI interfaces for CHAR protocol operations: ballot propagation, leader advertisements, state inspection, and operator commands - Design storage and indexing systems for protocol state: bond tracking, ballot history, and attestation persistence with reorg resilience - Develop comprehensive testing infrastructure: multi-node simulation, edge case coverage, fuzzing, and DoS scenario validation; conduct rigorous code reviews across the entire stack ## What We’re Looking For Must-Haves - Strong systems programming skills in C++ with a focus on correctness, performance, and memory safety - Experience with low-level programming: memory management, concurrency primitives, performance profiling - Comfort working across the stack including cryptographic primitives, networking, storage, and build systems - Strong problem-solving instincts and the ability to debug complex, multi-layered systems - Collaborative mindset; you give and receive code review feedback constructively Nice-to-Haves - Experience building Bitcoin applications or familiarity with Bitcoin Core codebase - Practical 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 tolerance - Experience designing and implementing P2P protocols for custom messages and state propagation - Contributions to open-source projects in the Bitcoin or broader crypto ecosystem - Understanding of timelock-based economic mechanisms and slashing conditions Reading Materials - Position: Senior Researcher / Scientist  ·  Location: Miami, FL strongly preferred  ·  Project: Char Network ## About Char Network Char 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 and applications. We’re a small, sharp, and adventurous team led by Bitcoin developer [Jeremy Rubin](https://rubin.io/), 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 means working at the frontier of Bitcoin R&D and infrastructure. ## About the Role This role sits at the intersection of research and engineering. You'll invent, formalize, and validate the core protocols that make Char Network work—from Byzantine fault tolerant consensus to staking incentive mechanisms to cryptographic proof systems. Your focus is on the cryptographic foundations that make Char's protocol secure and efficient: designing and analyzing commitment schemes, aggregation protocols, proof systems, and fork-free coordination mechanisms. You'll work closely with the core protocol team to turn research into hardened, shipping software by building simulations, prototypes, and security specifications that guide implementation. This is not a pure theory role, you'll write code. ## What You’ll Do - Design and analyze cryptographic schemes: BLS proof-of-stake commitments, signature aggregation protocols, hash-based accumulator designs, and zero-knowledge proof systems for Bitcoin anchoring - Formalize consensus protocols for protocol security: fork-free properties, Byzantine fault tolerance guarantees, and commitment finality, with rigorous threat modeling and adversarial analysis - Develop and validate cryptographic implementations: work with the protocol team to guide BLS [Purify](https://judica.org/purify/) integration, verify protocol specifications against implementation, and conduct security reviews - Build simulations and prototypes in Rust or C++ to validate cryptographic protocol designs under adversarial conditions: analyze safety/liveness properties and attack resilience - Conduct formal cryptographic security analysis: threat modeling, game-theoretic attack analysis, and stress-testing through simulation and fuzzing to identify vulnerabilities before shipping ## What We’re Looking For Must-Haves - Deep expertise in applied cryptography: signature schemes, commitment schemes, zero-knowledge proofs, or cryptographic protocol design - Expert-level understanding of distributed systems theory: BFT consensus, fork-free protocols, Byzantine fault tolerance, and formal safety/liveness analysis - Strong programming skills in Rust or C++ (or equivalent systems languages) - Experience designing, analyzing, or breaking adversarial cryptographic protocols or consensus systems - Ability to move between theory and practice: formal reasoning, mathematical modeling, and implementation - Exceptional communication skills—you can explain complex cryptographic ideas clearly to both researchers and engineers Nice-to-Haves - PhD or equivalent research experience in cryptography, distributed systems, or a related field - Prior contributions to Bitcoin, Ethereum, or other consensus-critical software - Experience with formal verification, model checking, or advanced testing frameworks - Published papers, technical reports, or BIPs in cryptography or distributed systems - Understanding of Bitcoin primitives: taproot, timelocks, covenant designs, transaction scripting - Experience with game-theoretic analysis or mechanism design (helpful for understanding protocol incentives) - Strong open-source collaboration background Reading Materials Char Network - https://www.youtube.com/live/bi1XJRR9GDg?si=LURoAKAlWm49ahuY&t=4469 - [Ember Consensus Paper](https://char.network/whitepaper/char_ember_consensus_paper.pdf) - [Purify in purify-cpp](https://judica.org/purify/paper/purify-paper.pdf) BitVM - [BitVM Whitepaper](https://bitvm.org/bitvm.pdf)+ [BitVM2 Whitepaper](https://bitvm.org/bitvm_bridge.pdf) - [BitVM High-Level Explainer](https://bitcoinmagazine.com/technical/the-big-deal-with-bitvm-arbitrary-computation-now-possible-on-bitcoin-without-a-fork) ## About Char Network ## Company Overview - **One-liner**: Char Network is building a proof-of-stake application coordination protocol that lets rollups and applications coordinate outcomes on Bitcoin without changing Bitcoin’s base-layer rules. - **Entity Type**: Private (Startup, early-stage) - **Headquarters**: Miami, Florida, United States - **Founded**: Not publicly available - **Founders**: Led by Bitcoin developer Jeremy Rubin ## Core Business - Primary industry: Blockchain infrastructure / Bitcoin Layer 2 protocol development - Target customers: Developers building rollups, bridges, and applications on Bitcoin; node operators who stake BTC; enterprises needing verifiable coordination on Bitcoin - Mission or purpose statement: To provide a sequencing layer for Bitcoin, enabling verifiable coordination and outcome proofs without requiring softforks or protocol changes ## Products & Services - **Char Protocol**: A proof-of-stake application coordination protocol. Operators lock BTC as stake, sign updates, and produce verifiable outcome proofs (decision rolls) that any consumer can independently verify. Uses PureSign, a non-equivocation primitive, to cryptographically prevent double-signing. - **Domains**: Rollups and applications define a “domain” on Char, each with its own sequence of decisions. The first focus is validium-style rollups with precommitments. - **Decision Rolls**: Proof objects emitted once a 2/3 stake threshold is crossed, packaging signed updates and non-equivocation proofs for independent verification. - **BitVM Enforcement (Roadmap)**: Planned on-chain enforcement paths to enable slashing and economic penalties for misbehavior. - **Charmed VM + Reward Engine (Roadmap)**: Future virtual machine and incentive mechanisms for operators. ## Market Standing - **Valuation/Market Cap**: Not disclosed - **Key Metric**: Total Funding — Not publicly available; the company is in an early, prototype phase. - **Notable Investors/Partners**: Not publicly disclosed - **Growth Signals**: Open-source prototype shipped with BTC bonds, stake weighting, signed updates, P2P sync, ballots, decision rolls, and PureSign non-equivocation proofs. Actively hiring for 4 roles (Cryptography and Systems Researcher, Engineering Manager, Integrations Engineer, Protocol Core Engineer) as of mid-2026. Team is small, sharp, and led by well-known Bitcoin developer Jeremy Rubin. ## Competitive Advantages - **BTC-Secured Security**: Operators lock real BTC as stake, creating economic accountability without changing Bitcoin’s consensus. - **No Softfork Required**: Char runs as optional software alongside Bitcoin Core, using standard Bitcoin transactions for bonds. - **PureSign Non-Equivocation**: A novel cryptographic primitive that exposes an operator’s private key if they double-sign, providing strong fork-free guarantees. - **Deterministic, Stake-Weighted Leader Selection**: Anchored to the current Bitcoin block hash, ensuring predictable and verifiable coordination. - **First-Mover in Bitcoin Sequencing**: Focused specifically on Bitcoin-native sequencing and outcome proofs, a relatively new and underserved niche. ## Strategic Focus - **Hardening the Protocol**: Moving from prototype to production by implementing BitVM enforcement paths, completing the Charmed VM and reward engine, building verifier libraries and SDKs, and parameter hardening. - **Ecosystem Integration**: Building integrations with rollups, bridges, and other Bitcoin L2 applications. - **Research & Development**: Active focus on cryptographic foundations (BLS commitments, signature aggregation, zero-knowledge proofs, hash-based accumulators) and consensus protocol formalization. - **Talent Acquisition**: Building a small, elite team of protocol engineers, cryptographers, and systems researchers. ## Why Work Here - **Cutting-Edge Bitcoin R&D**: Work at the frontier of Bitcoin protocol development, contributing to infrastructure that could power the next generation of Bitcoin L2s. - **Small, High-Impact Team**: A “small, sharp, and adventurous” crew where every contribution counts and every voice matters. Fast-moving and collaborative culture. - **Led by a Notable Bitcoin Developer**: Jeremy Rubin is a well-known figure in the Bitcoin space, offering mentorship and deep protocol expertise. - **Miami, FL Headquarters**: Office location in Miami with roles strongly preferred to be on-site. Miami is a growing hub for crypto and blockchain companies. - **Compensation**: Cryptography and Systems Researcher role estimated at $72k–$150k per year (from web3.career listing). - **Open Source & Research-Focused**: The work blends deep protocol expertise with a hacker’s creativity — ideal for engineers who enjoy hard problems and bold ideas. - **Flexible Roles**: Positions range from pure research to hands-on engineering, with an emphasis on moving between theory and practice. ## Sources 1. [char.network](https://char.network/) 2. [Greenhouse Job Board](http://job-boards.greenhouse.io/charnetwork) 3. [Cryptography and Systems Researcher Job Posting](https://job-boards.greenhouse.io/charnetwork/jobs/4210315009) 4. [Workforce Miami Company Profile](https://dashboard.workforce.miami/companies/415a2350-a7ed-40a5-8342-cd1612609e61) 5. [Web3 Career Listing](https://web3.career/cryptography-and-systems-researcher-charnetworklabs/149309) ## Other roles at Char Network - [Cryptography and Systems Researcher](https://feeny.ai/job/cryptography-and-systems-researcher-char-network-miami-florida-6qym325yvk3k) — Miami Florida, United States