Senior Security Engineer - xStocks

As a Senior Security Engineer at Ink Foundation's xStocks platform, you own security end to end while shipping products alongside the engineering team. xStocks brings real-world assets on-chain as tokenized securities regulated and fully-backed across multiple blockchains including EVM, Solana, TON, and Tron. You report into engineering and partner closely with Payward's security, CISO, and compliance functions in a role built for someone who is genuinely both engineer and security specialist.

What you'll do

• Own security deliverables end to end: coordinate and review smart-contract audits, respond to security questionnaires and due-diligence requests, support CISO and compliance initiatives, and drive findings to tracked, closed-out fixes.
• Run offensive assessments against your own platforms, pentesting web apps, APIs, backend services, and on-chain components, and build tooling to do it repeatedly rather than once.
• Continuously assess security posture through threat modeling new and existing systems, reviewing architecture and key-management flows, and maintaining a living view of risks and mitigations.
• Review code for security as a default reviewer on changes touching authentication, cryptography, custody, signing, and fund movement across chains.
• Harden the platform by improving secrets handling, IAM and least-privilege, dependency and supply-chain hygiene, and detection and logging for security-relevant events.
• Secure custody and signing workflows by reviewing and hardening transaction signing flows, MPC and HSM integrations, signer permissions, admin roles, approval policies, and break-glass procedures.
• Contribute to product engineering by picking up regular backlog work in TypeScript to stay close to the codebase you defend.
• Support incidents through detection, triage, response, and post-mortems, feeding lessons back into the program.

What you bring

• Production engineering strength: you write and review code comfortably in TypeScript and Node.js, and understand systems deeply enough to break them.
• Strong application and infrastructure security fundamentals covering OWASP-class vulnerabilities, authentication and authorization, injection, SSRF, supply-chain risk, and secure design, with real offensive work in pentesting, vulnerability research, or red-team experience.
• Applied cryptography and blockchain security knowledge: symmetric and asymmetric primitives, hashing, signatures, key management, plus the security model of EVM, Solana, and ideally TON or Tron, and the ability to read a smart contract and reason about how it fails.
• Ownership: you can take an ambiguous security item, an audit, a questionnaire, or an incident and drive it to closure without being managed through it.
• Clear communication: you explain risk to engineers, to a CISO, and to an auditor, tailoring the message to each audience.
• An automation instinct: you turn findings into tests, alerts, controls, documentation, or platform improvements rather than catching the same issue manually twice.
• Risk judgment: you distinguish theoretical issues from material ones and communicate severity, likelihood, impact, and remediation tradeoffs clearly.

Nice to have

• Experience commissioning or remediating third-party smart-contract audits.
• Familiarity with custody and signing infrastructure such as HSMs, MPC, and ForDefi-style providers, and with on-chain transaction security.
• Cloud security depth in GCP or AWS, including IAM, container, and runtime hardening.
• Detection engineering and security observability experience, including SIEM and log-based detections.
• Relevant certifications such as OSCP, OSWE, or GWAPT.
• Prior work in a regulated fintech or tokenization/DeFi environment.

About Ink Foundation

Ink Foundation (Payward) has spent 15 years building one of the most modern and globally accessible financial infrastructure platforms in the industry. The organization includes Kraken, NinjaTrader, Breakout, xStocks, Payward Services, and CF Benchmarks, and is committed to advancing an open, global financial system.