**Why**:
To provide an additional layer of security.
The TOTP spec (RFC 6238) recommends encrypting the keys.
http://tools.ietf.org/html/rfc6238
**How**:
Borrow the encryption code from the `attr_encrypted` gem and use it to
encrypt and decrypt the `otp_secret_key` attribute.
Allow users to add encryption by passing in `encrypted: true` to
`has_one_time_password`. This provides backwards-compatibility for
existing users of the gem.
See the README updates for more detailed instructions for both new
and existing users.
This makes the gem store a signed cookie for a configurable amount of
time that allows the user to bypass 2FA. Our use-case for this is that
we expire user’s Devise sessions after 12 hours, but don’t want to
force them to authenticate using 2FA every day.
Signed cookies are available since Rails 3. This requires the signing
functionality to be properly configured, but is disabled by setting the
config variable to `0`, the default.
Moncef Belyamani
Paul Bowsher
Dmitrii Golub
Ross Kaffenberger
Matt Mueller