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Core Protocol Engineer
Position: Senior Engineer
- Location: Miami, FL strongly preferred
- Project: 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
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
- 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
- Char Network — MIT Bitcoin Expo Presentation (2026)
- BitVM Whitepaper + BitVM2 Whitepaper
- BitVM High-Level Explainer
- Purify Library
What is Zero-knowledge?
Zero-knowledge is a concept in cryptography that allows two parties to exchange information without revealing any additional information beyond what is necessary to prove a particular fact
In other words, zero-knowledge is a way of proving something without actually revealing any details about the proof
Here are some examples of zero-knowledge:
- Password authentication: When you enter your password to log into an online account, the server doesn't actually know your password. Instead, it checks to see if the hash of your password matches the stored hash in its database. This is a form of zero-knowledge because the server doesn't know your actual password, just the hash that proves you know the correct password.
- Sudoku puzzles: Suppose you want to prove to someone that you've solved a particularly difficult Sudoku puzzle. You could do this by providing them with the completed puzzle, but that would reveal how you solved it. Instead, you could use a zero-knowledge proof where you demonstrate that you know the solution without actually revealing the solution itself.
- Bitcoin transactions: In a Bitcoin transaction, you prove that you have ownership of a certain amount of Bitcoin without revealing your private key. This is done using a zero-knowledge proof called a Schnorr signature, which allows you to prove ownership of a specific transaction output without revealing the private key associated with that output.
- Secure messaging: In a secure messaging app, you can prove to your contacts that you have access to a shared secret without revealing the secret itself. This is done using a zero-knowledge proof, which allows you to prove that you have access to the secret without actually revealing what the secret is.