What is OneTimePass

OneTimePass (actually onetimepass) is a module for generating one-time passwords, namely HOTPs (HMAC-based one-time passowords) and TOTPs (time-based one-time passwords). They are used eg. within Google Authenticator application for Android or iPhone.

How to use OneTimePass

You can use this module in the following way:

1. Install module (download it into your application's directory or into modules directory)

2. To get time-based token you invoke it like that:

    import onetimepass as otp
    my_secret = 'MFRGGZDFMZTWQ2LK'
    my_token = otp.get_totp(my_secret)
   

3. To get HMAC-based token you invoke it like that:

    import onetimepass as otp
    my_secret = 'MFRGGZDFMZTWQ2LK'
    my_token = otp.get_hotp(my_secret, intervals_no=3)
   

   where intervals_no is the number of the current trial (if checking on the server, you have to check several values, higher than the last successful one, determined for previous successful authentications).

4. To check time-based token you invoke it like that:

    import onetimepass as otp
    my_secret = 'MFRGGZDFMZTWQ2LK'
    my_token = 123456 # should be probably from some user's input
    is_valid = otp.valid_totp(token=my_token, secret=my_secret)
   

5. To check HMAC-based token you invoke it like that:

    import onetimepass as otp
    my_secret = 'MFRGGZDFMZTWQ2LK'
    my_token = 123456 # should be probably from some user's input
    last_used = 5 # store last valid interval somewhere else
    is_valid = otp.valid_hotp(token=my_token, secret=my_secret, last=last_used)
   

   where:

   • last argument (in this case being assigned last_used) is the number of the last successfully checked interval number (as valid_totp() will skip it and start checking from the next interval number)
   • is_valid is being assigned value of False if my_token has not been identified as valid OTP for given secret (my_secret) and checked interval range. If it has been successful, is_valid is assigned a number of the working interval number (it should be saved into the database and supplied to the function as last argument next time the password is being checked, so you cannot use the same token again).