NeylanCosta
  • Web3 Developer
  • Blockchain Engineer
  • Privacy & ZK Systems
  • FHE Cryptography
  • Educator

Building privacy-first decentralized systems — from FHE confidential tokens on Solana to ZK proof circuits on EVM. 8+ years shipping production-grade blockchain infrastructure.

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Selected Work

Projects

All Repositories ↗
022026

ciFHEr

Confidential Token on Solana using Fully Homomorphic Encryption

A fully-collateralized privacy wrapper for SOL where balances and transfer amounts live on-chain as genuine FHE ciphertexts. Validators and observers see only encrypted bytes — additions and subtractions happen homomorphically without ever decrypting.

  • Homomorphic arithmetic via tfhe-rs 0.7 — encrypted balances operated on without decryption at any point
  • Chunked ciphertext write system to fit 16 KB FHE blobs within Solana's 1,232-byte tx constraint (880B/tx)
  • Full production stack: Anchor programs, off-chain Node.js worker, Rust FHE sidecar, React + Phantom frontend
  • 10 passing integration tests on devnet
RustAnchortfhe-rsTypeScriptReactSolana

🏆 SuperteamBR Winner

BHOnchain 2026

032024

Swirl

ZK Privacy Pool on Mantle Network

Fixed-denomination privacy pool for MNT using Poseidon hashing and Noir ZK proofs to fully unlink deposits from withdrawals on-chain.

  • Poseidon-based incremental Merkle tree (depth 20, 1M leaves) for commitment storage
  • Complete Noir circuit: proves secret/nullifier preimage + Merkle inclusion, compiled to Solidity verifier via Barretenberg
  • Nullifier system preventing double-spends with zero on-chain linkage to deposit address
SolidityNoirPoseidonTypeScriptGraphQL
See more projects ↗

Background

About

Results-driven Web3 developer and educator with 8+ years of freelance software engineering experience. Specialist in smart contract architecture, privacy-preserving systems, on-chain data engineering, and EVM tooling.

Based in Rio de Janeiro, Brazil. Holds a B.Sc. in Applied and Computational Mathematics (UFRRJ) and Graduate Studies in Systems and Computer Engineering (UFRJ).

Active Web3 educator — teaching at iRede Web3.0, mentoring at Instituto Web3EduBrasil, and coaching teams at national hackathons.

Chains

EthereumSolanaStellarMantleAvalancheBase

8+

Years experience

6

Chains deployed

Hackathon winner

Technical Skills

Blockchain / EVM

SoliditySmart ContractsDeFi ProtocolsERC-20 / 721 / 1155HardhatFoundrySlitherMythril

Privacy & Cryptography

Zero-Knowledge ProofsNoirCircomFHE — tfhe-rsPoseidon HashingZK Circuit DesignIncremental Merkle Trees

Solana / Rust

Anchor FrameworkRustSPL TokensSolana Account ModelProgram Development

Stellar / Soroban

Soroban ContractsSoroban SDKStellar SDKXLM / USDC AssetsSEP StandardsTestnet Deployment

Frontend & Web3

TypeScriptReactNext.jsViemEthers.jsWeb3.jsNode.jsDApp Development

Backend & Data

PythonFastAPIFlaskTrading BotsData PipelinesREST APIsAutomation

Career

Experience

2026Education

Web3 Instructor & Mentor

iRede Web3.0

  • Teaching a structured curriculum: smart contract development, DApp architecture, and blockchain fundamentals
  • Delivering code reviews, live debugging sessions, and one-on-one mentoring
  • Developing exercises reinforcing Solidity, Ethers.js, and EVM concepts
  • Supporting students through end-to-end decentralized application capstone projects
2025 —Community

Mentor

Instituto Web3EduBrasil

  • Blockchain education events promoting Web3 adoption across Brazil
  • Hands-on workshops: smart contract development, DApp architecture, ZK proofs
  • Guiding developers through practical exercises in Solidity and on-chain system design
Mar 2026Mentorship

Hackathon Mentor

Monad Blitz Brazil

  • Mentored competing teams at two events (Rio de Janeiro & São Paulo)
  • Coached participants on security best practices, rapid prototyping, and MVP delivery
  • Hands-on support with Solidity debugging, contract optimization, and Web3 integrations
2019 —Engineering

Web3 Developer & Full-Stack Engineer

Freelance — Global Clients

  • Production smart contracts on Ethereum and EVM-compatible chains — DeFi and NFT protocols
  • High-performance automation scripts, trading bots, and on-chain data extractors in Python
  • Full-stack DApp frontends, dashboards, and Ethers.js/Web3.js integrations for DeFi, gaming, and NFT clients
  • 2D/3D multiplayer games using Godot and Unity, handling networking, gameplay logic, and deployment

Education

Graduate Studies — Systems and Computer Engineering

Universidade Federal do Rio de Janeiro (UFRJ)

2019 – 2024

B.Sc. — Applied and Computational Mathematics

Universidade Federal Rural do Rio de Janeiro (UFRRJ)

2019 – 2024

Competitions

Hackathons

2× Winner
5+ Events
DateEventProjectResult

2026

BHOnchain 2026

SuperteamBR Track · Belo Horizonte, Brazil

ciFHEr

🏆 Winner

2026

ETH Global OpenAgents

Agentic Systems · Remote

AI agent trading war simulation using Uniswap API

Participant

2025

ETHLatam

Base Miniapp Track · São Paulo, Brazil

Base miniapp

🏆 Winner

2025

ETH Global HackMoney

DeFi Systems · Remote

DeFi macro system — atomic multi-operation execution in a single transaction

Participant