Cryptography / Full-time
Applied Cryptography Engineer, Receipts and Verification
Design and harden the Ed25519-signed JWS receipts, hourly Merkle trees and the open-source verifier auditors use to check proof of residency.
Team
Cryptography
Location
Chennai
Type
Full-time
Posted
15 Oct 2026
- Own the receipt format: the canonical serialization of fields such as request hash, policy pack version, provider region, facility and upstream TLS certificate thumbprint, and its versioning rules.
- Maintain the hourly SHA-256 Merkle tree construction, root publication and inclusion proof generation, and test them against malformed and adversarial inputs.
- Develop ytt-verify, the open-source offline verifier, with reproducible builds and documentation an external auditor can follow without our help.
- Design key management for signing keys across SaaS regions and customer-held HSMs on Sovereign Dedicated, including rotation, revocation and key transparency.
- Keep receipt minting inside the gateway's latency budget by profiling signing and hashing on the hot path.
- Write the threat models and design notes that go into customer security reviews and our own SOC 2 and ISO 27001 evidence.
- Three or more years building production systems that use cryptography, such as signing services, transparency logs, PKI or secure messaging.
- Solid understanding of Ed25519 and EdDSA, JWS and JOSE, SHA-256, Merkle trees and inclusion or consistency proofs, and of the ways each can be misused.
- Strong Go or Rust, with tests that cover failure paths and not only the happy path.
- Experience with HSMs or cloud KMS, PKCS#11 or equivalent interfaces, and key ceremony procedures.
- The habit of writing down assumptions, so a reviewer outside the team can check them.
- Contributions to Certificate Transparency, Sigstore or another transparency log project.
- Experience with formal verification, fuzzing or property-based testing of parsers and serializers.
- Familiarity with eIDAS qualified timestamps or trust services.
- 01Application review
- 02Intro call
- 03Paid work sample
- 04Panel
- 05Offer