# The Ruby One Time Password Library
A ruby library for generating and validating one time passwords (HOTP & TOTP) according to [RFC 4226](http://tools.ietf.org/html/rfc4226) and [RFC 6238](http://tools.ietf.org/html/rfc6238).
ROTP is compatible with [Google Authenticator](https://github.com/google/google-authenticator) available for [Android](https://play.google.com/store/apps/details?id=com.google.android.apps.authenticator2) and [iPhone](https://itunes.apple.com/en/app/google-authenticator/id388497605) and any other TOTP based implementations.
Many websites use this for [multi-factor authentication](https://www.youtube.com/watch?v=17rykTIX_HY), such as GMail, Facebook, Amazon EC2, WordPress, and Salesforce. You can find a more complete [list here](https://en.wikipedia.org/wiki/Google_Authenticator#Usage).
## Dependencies
* OpenSSL
* Ruby 2.0 or higher
## Breaking changes
### Breaking changes in >= 6.0
- Dropping support for Ruby <2.3
### Breaking changes in >= 5.0
- `ROTP::Base32.random_base32` is now `ROTP::Base32.random` and the argument
has changed from secret string length to byte length to allow for more
precision. There is an alias to allow for `random_base32` for the time being.
- Cleaned up the Base32 implementation to match Google Authenticator's version.
### Breaking changes in >= 4.0
- Simplified API
- `verify` now takes options for `drift` and `after`
- `verify` returns a timestamp if true, nil if false
- Dropping support for Ruby < 2.0
- Docs for 3.x can be found [here](https://github.com/mdp/rotp/tree/v3.x)
## Installation
```bash
gem install rotp
```
## Library Usage
### Time based OTP's
```ruby
totp = ROTP::TOTP.new("base32secret3232", issuer: "My Service")
totp.now # => "492039"
# OTP verified for current time - returns timestamp of the current interval
# period.
totp.verify("492039") # => 1474590700
sleep 30
# OTP fails to verify - returns nil
totp.verify("492039") # => nil
```
### Counter based OTP's
```ruby
hotp = ROTP::HOTP.new("base32secretkey3232")
hotp.at(0) # => "786922"
hotp.at(1) # => "595254"
hotp.at(1401) # => "259769"
# OTP verified with a counter
hotp.verify("259769", 1401) # => 1401
hotp.verify("259769", 1402) # => nil
```
### Preventing reuse of Time based OTP's
By keeping track of the last time a user's OTP was verified, we can prevent token reuse during
the interval window (default 30 seconds)
The following is an example of this in action:
```ruby
user = User.find(someUserID)
totp = ROTP::TOTP.new(user.otp_secret)
totp.now # => "492039"
# Let's take a look at the last time the user authenticated with an OTP
user.last_otp_at # => 1432703530
# Verify the OTP
last_otp_at = totp.verify("492039", after: user.last_otp_at) #=> 1472145760
# ROTP returns the timestamp(int) of the current period
# Store this on the user's account
user.update(last_otp_at: last_otp_at)
# Someone attempts to reuse the OTP inside the 30s window
last_otp_at = totp.verify("492039", after: user.last_otp_at) #=> nil
# It fails to verify because we are still in the same 30s interval window
```
### Verifying a Time based OTP with drift
Some users may enter a code just after it has expired. By adding 'drift' you can allow
for a recently expired token to remain valid.
```ruby
totp = ROTP::TOTP.new("base32secret3232")
now = Time.at(1474590600) #2016-09-23 00:30:00 UTC
totp.at(now) # => "250939"
# OTP verified for current time along with 15 seconds earlier
# ie. User enters a code just after it expired
totp.verify("250939", drift_behind: 15, at: now + 35) # => 1474590600
# User waits too long. Fails to validate previous OTP
totp.verify("250939", drift_behind: 15, at: now + 45) # => nil
```
### Generating a Base32 Secret key
```ruby
ROTP::Base32.random # returns a 160 bit (32 character) base32 secret. Compatible with Google Authenticator
```
Note: The Base32 format conforms to [RFC 4648 Base32](http://en.wikipedia.org/wiki/Base32#RFC_4648_Base32_alphabet)
### Generating QR Codes for provisioning mobile apps
Provisioning URI's generated by ROTP are compatible with most One Time Password applications, including
Google Authenticator.
```ruby
totp = ROTP::TOTP.new("base32secret3232", issuer: "My Service")
totp.provisioning_uri("alice@google.com") # => 'otpauth://totp/My%20Service:alice%40google.com?secret=base32secret3232&issuer=My%20Service'
hotp = ROTP::HOTP.new("base32secret3232", issuer: "My Service")
hotp.provisioning_uri("alice@google.com", 0) # => 'otpauth://hotp/alice%40google.com?secret=base32secret3232&counter=0'
```
This can then be rendered as a QR Code which the user can scan using their mobile phone and the appropriate application.
#### Working example
Scan the following barcode with your phone, using Google Authenticator
Now run the following and compare the output
```ruby
require 'rubygems'
require 'rotp'
totp = ROTP::TOTP.new("JBSWY3DPEHPK3PXP")
p "Current OTP: #{totp.now}"
```
### Testing
```bash
bundle install
bundle exec rspec
```
### Testing with Docker
In order to make it easier to test against different ruby version, ROTP comes
with a set of Dockerfiles for each version that we test against in Travis
```bash
docker build -f Dockerfile-2.6 -t rotp_2.6 .
docker run --rm -v $(pwd):/usr/src/app rotp_2.6
```
Alternately, you may use docker-compose to run all the tests:
```
docker-compose up
```
## Executable Usage
The rotp rubygem includes CLI version to help with testing and debugging
```bash
# Try this to get an overview of the commands
rotp --help
# Examples
rotp --secret p4ssword # Generates a time-based one-time password
rotp --hmac --secret p4ssword --counter 42 # Generates a counter-based one-time password
```
## Contributors
Have a look at the [contributors graph](https://github.com/mdp/rotp/graphs/contributors) on Github.
## License
MIT Copyright (C) 2019 by Mark Percival, see [LICENSE](https://github.com/mdp/rotp/blob/master/LICENSE) for details.
## Other implementations
A list can be found at [Wikipedia](https://en.wikipedia.org/wiki/Google_Authenticator#Implementations).
Generated by dwww version 1.15 on Sat Aug 30 16:23:51 CEST 2025.