is it possible to have 4 digit token, not 6

[almeynman]

So basically I want to generate 4 digit code instead of 6 and also want to control expiration

[yuce]

That is not possible with this library which implements HOTP algorithm. 6 digits is the minimum. See: https://en.wikipedia.org/wiki/HMAC-based_One-time_Password_Algorithm

[almeynman]

Thanks for the link. I guess will have to stick with 6.
I have one more question: is it possible to control expiration time? i.e. 30 minutes, 1 hour. Currently it seems like the code expires in a minute or even less

[yuce]

Sorry, I was wrong on the token length. You can specify the token length by passing e.g., {token_length, Length} in a proplist, like: pot:totp(Secret, [{token_length, 4}]).. And token expiration with {interval_length, Seconds}, .e.g: pot:totp(Secret, [{token_length, 4}, {interval_length, 3600}]).. But specifying these settings may create tokens incompatible with Google Authenticator, in case you care.

[almeynman]

Oh thanks! Thats what I was looking for