Open Source / radAuthenticator
A Delphi sample that generates Time-based One-Time Password (TOTP) codes compatible with Google Authenticator — the same rotating six-digit codes users already scan into their phones for two-factor authentication. It is a complete, readable walk-through of how 2FA actually works, in plain Object Pascal.
Behind every authenticator app is a small, well-specified algorithm: a shared secret, the current time, and an HMAC reduced to a handful of digits. radAuthenticator implements exactly that in Delphi, producing codes that verify against Google Authenticator and any RFC 6238-compliant server.
Time-based one-time passwords per RFC 6238, built on the HOTP (RFC 4226) HMAC construction — the same math the big authenticator apps use.
Codes are interoperable with Google Authenticator and compatible apps, so you can validate the implementation against tools you already trust.
Kept deliberately generic and clear — no vendor marks, no magic. A dependable starting point for adding 2FA to your own Delphi apps.
radAuthenticator grew out of a five-part series on ideasawakened.com that builds the whole thing step by step — from the underlying algorithm to a working app. Read it front to back, or jump to the code.