At Nethermind, Kalzak has worked across a range of DeFi and infrastructure projects, including smart wallets, derivatives, lending protocols, and cross-chain bridges. His responsibilities include vulnerability discovery, technical reporting, client collaboration, and smart contract monitoring through Forta-based detection agents.

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Kalzak is an active participant in the security and CTF community, ranking 7th on the Curta leaderboard and placing in the top 80 of Secureum Epoch 0. His research includes elliptic curve cryptography, reverse engineering, and zero-knowledge-related systems. He has also contributed to multiple open-source and experimental projects, including raw bytecode ERC-20 implementations, gas optimization research, and developer tooling.

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His technical stack includes Solidity, Huff, Rust, Cairo, and low-level EVM tooling, with a focus on performance, correctness, and exploit prevention in production blockchain systems.