Senior Software Engineer (Security)

Apply on our website: https://www.allthenticate.com/careers/elite-software-engineer

Allthenticate is replacing passwords with the phone in your pocket. Our products unlock computers, sign people into their apps, and open doors, all without a password. We're a small, fast-moving team in Houston, TX.

What you'll do
You'll own the deepest, most security-critical parts of Allthenticate: the code that sits between a phone and a computer's login screen. That means Rust running inside Windows as a credential provider, LSA authentication package, and CNG key storage provider. It means a Python service that talks Bluetooth to phones on Windows, macOS, and Linux. And it means the certificate and identity plumbing that lets an employee sign into an Entra ID joined laptop with nothing but their phone. When a Windows update breaks sign-in, or a customer needs certificate logon to work against their own CA, you're the one who figures out why and fixes it for good.

Responsibilities

• Building and maintaining our Windows authentication stack in Rust: a credential provider, an LSA authentication package, and a CNG key storage provider
• Extending Windows sign-in for Entra ID and Active Directory, including certificate-based logon, Kerberos, PKI, and certificate revocation
• Developing our desktop service, an asyncio Python daemon that brokers authentication between phones and computers over Bluetooth Low Energy
• Working in our Rust cryptography core, shared with Python through PyO3 and with our Flutter mobile app through flutterrustbridge
• Shipping backend features in FastAPI and Flask, including SAML, OIDC, and WS-Federation identity flows
• Evolving the protobuf protocol that connects our mobile, desktop, and cloud components
• Hardening everything you touch through threat modeling, mTLS, and code review with an attacker's eye
• Packaging, signing, and testing releases for Windows, macOS, and Linux in CI

What we're looking for

• Strong systems programming skills in Rust, plus fluency in Python
• Real experience with Windows internals and authentication, such as Win32 APIs, credential providers, LSA, Kerberos, or smart card logon
• A solid security background: applied cryptography, PKI and X.509, authentication protocols, and how attackers break them
• Working knowledge of SAML, OIDC, and enterprise identity providers like Entra ID and Active Directory
• Hands-on experience using Claude or other AI agents to write, review, and debug code, and good judgment about when to trust them
• A generalist streak: you'd rather learn the unfamiliar part of the stack than hand the problem to someone else

Nice to have

• Windows security development: COM, LSA or SSP packages, CNG providers, or drivers
• Bluetooth Low Energy on BlueZ, WinRT, or CoreBluetooth
• Flutter and Dart, or Swift on macOS (CryptoTokenKit, launchd)
• Implementing FIDO2, WebAuthn, or passkeys
• Embedded Linux and over-the-air firmware updates
• A history of CVEs, open-source contributions, or side projects you can't stop talking about

Benefits
100% employer-covered health, dental, and vision; equity; 401(k) match; flexible hours.

Apply on our website: https://www.allthenticate.com/careers/elite-software-engineer