Railstutorial.org: Authentication only works in the same device as created

I have followed the railstutorial.org in creating my own authentication system but it loo开发者_如何学运维ks like there's an error.

The sign_in only works when the user has been created in the same device.

e.g:

1) I deploy the app to heroku

2) I create the user on my MAC

3) I try to sign in on my iPhone

4) Failure.

Link : http://railstutorial.org/chapters/sign-in-sign-out#top

The same happens if you replace "my MAC" for iPhone of for any other computer.

Could it be because of sessions?

What could be causing this?

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I know this doesn't solve the problem directly but why not try a prebuilt authentication system like devise. People have put a lot of effort into solving many of the issues that you might come across and it seems crazy to re-create the wheel in terms of login.