SimpleHOTP

A lightweight HOTP (HMAC - Based one Time Password) Generator for Arduino.
This library is for those, who want to save on memory and still use HOTPs, as there are no heavy third-party dependencies included.

Please note, that C++11 must be enabled with Arduino IDE. This is enabled by default as of version 1.6.6.

Functionalities

Anyone is welcome to add to the functionalities and report on any issues.

1. Generate fast and easy a HOTP with the secret key and the counter value
2. Validate easily an entered HOTP with the secret key, the counter and and the resync look-ahead parameter
3. Generate Keys for use in SHA1-HMAC authentication
4. Generate SHA1-HMACs
5. Generate SHA1 kryptographic hashes of messages with a length of up to (2^64)-1 Bits

Usage

It can be as easy as this validation of a user provided hotp.

#include <SimpleHOTP.h>
int currentCounter = 3;

// ...

// load the key and the HOTP object
char secret[] = "secret passphrase";
Key key(secret, sizeof(secret)-1);
SimpleHOTP hotp(key, currentCounter);

int nextCounter = 0;
do {
    // getUserInput() as placeholder for your function!
    // it MUST return a 32-bit integer.
    nextCounter = hotp.validate(getUserInput());
} while (!nextCounter && !hotp.isLocked());

if (nextCounter) {
    // success
}
else {
    // failure
}

For more information on the usage please refer to the .h files in the /src directory.

Changelog

Only version changes as labeled in git are listed here. Version numbers are semantic.

1.0.1

README.md fixed for reference to documentation.

License

Developed by Jonathan Lusky
See the License information sheet