Cryptographer / Protocol Lead

About Cycles Cycles' mission is to clear the most debt, for the most people, with the least money. We're building a privacy-preserving on-chain protocol to enable arbitrary finance to occur in the most capital-efficient manner possible, by taking advantage of the liquidity saving effects of multilateral settlement. Cycles is an open clearing protocol that generalizes the capabilities of a clearing house while making them accessible to anyone. This requires solving a number of challenging protocol design problems at the intersection of cryptography, distributed systems, security, scalability, payment and financial system design. Cycles is an independent venture backed startup being incubated by Informal Systems. Cycles is backed by CMCC Global, Maven11, Compound VC, Primitive Ventures, Nascent and Cygni and is currently preparing for Series A. This role presents a rare opportunity to join a high-growth startup and be a part of the founding team led by Ethan Buchman, co-founder of Cosmos.

About the Role

We are looking for a Cryptographer and Protocol Lead to own the design, specification, and security of our protocol development. We take modern Shielded Pools (ZCash, Penumbra, Aztec) as our jumping off point, and have designed a first version of our Shielded Graph on top, which extends privacy from assets to past and future debts. The Cycles Protocol will underpin a host of new products that make the capabilities of clearing accessible across diverse user groups, from SMEs to multinationals, trading firms to clearing houses, municipalities to central banks. These products aim to revolutionize how people and businesses interact with money, clearing, and payments. The ideal candidates will have deep expertise in cryptography and privacy-preserving protocols, and a passion for elegant protocol design and security. You will work closely with cross-functional teams to deliver a scalable and secure protocol that powers transformative new products. What your primary responsibilities will be:

• Own our cryptography, proving, and protocol stack end-to-end
• Lead design and implementation of new primitives and protocols
• Write specs, develop security arguments, and apply formal methods (where applicable) to ensure soundness and security
• Review, audit, and improve existing designs and system implementations for security, performance, and scalability.
• Collaborate closely with product, engineering, and research teams: translate high-level product requirements into rigorous protocol designs, and partner with engineering to bring them to life
• Research new and emerging cryptographic techniques to advance performance,, developer experience, and scalability
• Mentor the team by guiding engineers and running workshops and deep dives
• Engage with the broader community: publish specs/papers, participate in protocol review cycles, open-source contributions, and stay abreast of state-of-the-art in cryptography and distributed systems.

What we look for in a successful Cryptographer and Protocol Lead:

• Passion for bringing advanced cryptography to life through delightful products and elegant protocols
• Degree in Cryptography, Computer Science, Mathematics, or a related field—with a strong publication track record in cryptographic protocols.
• Deep expertise in cryptographic primitives and protocols (e.g., zero-knowledge proofs, multiparty computation, shielded pool design, circuit design and optimization, etc.).
• Hands-on experience designing and implementing production-grade cryptographic systems or protocols at scale, especially decentralized ones
• Strong programming background (Rust) and familiarity with cryptographic libraries.
• Strong ability to write clear specifications, define invariants, reason about correctness, and use formal specification tools where appropriate.
• Ability to think both abstractly (protocol design, mathematics) and concretely (engineering trade-offs, performance, system integration).
• Excellent communication skills: you'll articulate complex cryptographic ideas to diverse audiences (product, engineering, security, external partners).
• Passion for pushing the boundaries on what's possible in security, privacy, decentralisation, and the future of cryptographic infrastructure.

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