teotipi

A Gleam CLI and library for generating TOTP codes (RFC 6238).

Usage

gleam run -- <base32-secret>

Example:

$ gleam run -- JBSWY3DPEHPK3PXP
123456

The secret is your Base32-encoded TOTP key (the one you'd scan as a QR code in an authenticator app).

Library API

import teotipi

// Returns a zero-padded 6-digit string
teotipi.totp_string("JBSWY3DPEHPK3PXP")  // Ok("123456")

// Returns a raw integer
teotipi.totp("JBSWY3DPEHPK3PXP")          // Ok(123456)

Both functions return Error(Nil) if the secret is not valid Base32.

How it works

Implements TOTP as defined in RFC 6238:

1. Decode the Base32 secret
2. Compute the time counter (unix_seconds / 30)
3. Run HMAC-SHA1 over the 64-bit counter
4. Apply dynamic truncation to extract a 6-digit code

Testing

gleam test

License

MIT — see LICENSE.