AOpass

AOpass, short for Adaptive One-time Password System, is a passwordless authentication protocol proposed for web and mobile services. It aims to provide phishing-resistant access by generating adaptive one-time codes on a user device and validating them on a server, with codes that are short-lived to prevent reuse. The design emphasizes binding authentication to the legitimate origin and to the user’s device, reducing the risk of credential interception or replay.

Technical overview: The protocol operates within a public-key framework where the device stores a private key or derived credential in a secure element, while the server stores the corresponding public key. During sign-in, the server issues a challenge; the client uses its secret to produce a response that typically combines a signed operation with an adaptive one-time code derived from a seed, a counter, or a timestamp. The server verifies the signature and validates the code’s freshness. Optional device attestation and user interaction strengthen trust and assurance of the originating device.

Relation to existing ecosystems: AOpass can be integrated with existing passwordless workflows and complements standards and practices such as WebAuthn by adding device-bound one-time codes to the challenge-response flow. It is designed to operate across online and, with careful design, offline-capable modes, though offline operation requires robust key storage and synchronization strategies.

Security and deployment considerations: Benefits include enhanced phishing resistance and reduced risk of credential reuse, but limitations involve dependence on secure element integrity, recovery procedures for lost devices, and potential onboarding friction. Effective implementations require careful key management, robust revocation processes, and defenses against side-channel or timing attacks to maintain security properties.