Shebin John

Senior Research Engineer, Safe · Bengaluru, India

I work on Safe's smart-account contracts, which we check with Certora formal verification and external audits. Since 2025 I have built transaction guards for Safe accounts (Guardrail, Fiducia and the Policy Engine) and, for Safenet, the staking contract on Ethereum mainnet and the Safenet Guard. I also coordinate Safe's third-party audits. Earlier at Safe I took the SAFE token locking contract from its first commit to mainnet and worked on the v1.5.0 core release and the ERC-4337 and passkey modules. Before Safe I did 15+ smart-contract audits at Nethermind and wrote production DeFi contracts at Sovryn. In 2020 I wrote and audited contracts at Kleros.

Focus

Smart-account infrastructure

Safe smart accounts held more than $100 billion in assets when Safe announced the milestone in March 2024. On those contracts I took about 2.7 KB off the singleton's deployed bytecode without changing its behavior and worked on the v1.5.0 release. For the ERC-4337 account-abstraction module I measured what user operations cost in gas.

Formal verification

I write Certora specs next to the contracts they check and update them when the code changes. I have done that for the token locking contract, the Safe core contracts, the ERC-4337 module, Guardrail and Safenet's staking contract and guard.

Security review

Before Safe I audited contracts: 11 published reports in 2020 for Kleros, CertiK and QuillHash, then Solidity and Cairo audits at Nethermind. At Safe I coordinate the third-party audits, fix findings in my own code and publish the audit reports.

Selected work

Safenet: staking contract and Safenet Guard

Safe's transaction-security network: validators attest to a Safe transaction, and a guard on the account checks the attestation onchain.

I wrote the staking contract that Safenet Beta runs on Ethereum mainnet and the Safenet Guard, with Certora specs for both. Certora audited both contracts, and Nethermind audited the protocol in September 2026.

Safe guards: Guardrail, Fiducia and the Policy Engine

Three transaction guards for Safe accounts: a DELEGATECALL allowlist, a delay on new kinds of transactions and a policy engine.

I started all three repositories and wrote most of their commits. Certora audited the Policy Engine in August and September 2026.

Safe token locking contract

A contract on Ethereum mainnet that locks SAFE tokens, with a cooldown between unlock and withdrawal.

I set up the repository, implemented lock, unlock and withdraw, and wrote Certora rules for them. Ackee and Certora audited it before the v1 mainnet release.

Safe v1.5.0 release line

A release of the Safe core contracts, audited by Certora and Ackee.

I added the extensible fallback handler to the core repository and fixed 12 of Certora's audit findings. I also integrated Certora's verification of the migration contract and added the deployment addresses.

All selected work

Experience

  1. to present

    Senior Research Engineer, Safe

    Wrote Safenet's staking contract, live on Ethereum mainnet, and the Safenet Guard. Built three transaction guards: Guardrail, Fiducia and the Policy Engine. Coordinated the 2026 audits of the Safe core contracts, modules, Policy Engine and Safenet.

  2. to

    Senior Solidity Engineer, Safe

    Wrote the design spec for the token locking contract and took it to Ethereum mainnet. Cut about 2.7 KB from the Safe singleton's bytecode. Worked on the v1.5.0 core contracts, the ERC-4337 and passkey modules, Certora specs and audit fixes.

  3. to

    Smart Contract Auditor, Nethermind

    Did 15+ audits across Solidity and Cairo. Spoke on a Hindi livestream in Nethermind's online event series for India.

  4. to

    Lead Contributor, Origins DAO

    Led a distributed team building the Origins launchpad and was lead developer of its contracts.

  5. to

    Lead Smart Contract Engineer, Sovryn

    Audited Sovryn's governance, staking and vesting contracts. Wrote the Escrow, LockedSOV and Origins sale contracts, and the Development Fund contract, which held more than 45 million SOV that Sovryn valued at $1.8 billion at SOV's peak price. Led the Circle of Order, the production and maintenance team (Sovryn blog, July 2021).

  6. to

    Smart Contract Developer and Auditor, Kleros

    Audited Kleros Liquid, the MiniMe token, ERC-792 contracts and Gnosis Conditional Tokens, among others. Wrote the Blockhash RNG fallback range and escrow fee-recipient contracts, and built OmenFarming, a liquidity-reward dashboard that reads The Graph's GraphQL subgraphs.

  • Earlier: Regional Ambassador Lead at Waves Platform, 2018 to 2019. Founder of Texploxe, 2017 to 2019.
  • B.Tech in Computer Science and Engineering, Mangalam College of Engineering, 2013 to 2017.

Talks and writing

In November 2025 I gave the talk "Guarding the Safe: From Guardrail to Policy Engine" at the DeFi Security Summit in Buenos Aires. The same month I was the guest on episode 100 of The Accountant Quits, talking about operational security for onchain treasuries. In 2023 I spoke on a Nethermind livestream in Hindi, and in 2020 I wrote about my time at Kleros for its blog.

All talks and writing

Contact

admin@remedcu.com

Email me about smart-account security, formal verification or protocol design. Conference and podcast invitations are welcome, and so are requests to review public code.