Char Network

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, 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, 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 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
  
  • MIT Bitcoin Expo Presentation (April 2026)
  • Ember Consensus Paper
  • Purify in purify-cpp
  
  BitVM
  
  • BitVM Whitepaper + BitVM2 Whitepaper
  • BitVM High-Level Explainer