Library to generate Time-based One-Time Passwords.

Implements the Time-based One-Time Password algorithm specified in RFC 6238. Supports different time steps and it's compatible with tokens that uses the same standard (including software ones, like the Google Authenticator app).

Install the library using the Library Manager or manually in the \libraries folder of your IDE. This library requires the Cryptosuite library by maniacbug.

First, store your private key into an array:

uint8_t hmacKey[] = {0x4d, 0x79, 0x4c, 0x65, 0x67, 0x6f, 0x44, 0x6f, 0x6f, 0x72};

Then create a new instance of the TOTP class using one of the two available constructors:

TOTP(uint8_t* hmacKey, int keyLength);
TOTP(uint8_t* hmacKey, int keyLength, int timeStep);

The first assumes a timeStep of 30 seconds, value used for example by the Google Authenticator app.

Two methods are available to get a TOTP passcode:

char* getCode(long timeStamp);
char* getCodeFromSteps(long steps);

The first accept a unix timestamp (number of seconds since Epoch), the second the number of "steps" since Epoch (that is seconds / timeStep) and it's useful to get a pool of values.

http://www.lucadentella.it/2013/09/14/serratura-otp/

• Jose Damico, https://github.com/damico/ARDUINO-OATH-TOKEN
• Peter Knight, https://github.com/Cathedrow/Cryptosuite
• Maniacbug, https://github.com/maniacbug/Cryptosuite