If your master.key has been compromised, you might want to regenerate it.

No key regeneration feature at the moment. We have to do it manually.

1. Copy content of original credentials rails credentials:show somewhere temporarily.
2. Remove config/master.key and config/credentials.yml.enc
3. Run EDITOR=vim rails credentials:edit in the terminal: This command will create a new master.key and credentials.yml.enc if they do not exist.
4. Paste the original credentials you copied (step 1) in the new credentials file (and save + quit vim)
5. Add and Commit the file config/credentials.yml.enc

Important

• Make sure config/master.key is listed in .gitignore and NOT tracked by git.
• The command EDITOR=vim rails credentials:edit might not work if you require credential value in some file (initializers or database.yml). I had the problem with devise.rb. I just uncommented the line secret_key = ... just the time to run the command to regenerate the credentials file, and then commented the line out again.
• If you want to use Atom to edit the credentials, you can replace the command EDITOR=vim rails credentials:edit with:

  $ EDITOR="atom --wait" rails credentials:edit

• To set the ENV variable within Heroku, run:

  $ heroku config:set RAILS_MASTER_KEY=`cat config/master.key`

• To set the ENV variable within TravisCI, run:

  $ travis encrypt RAILS_MASTER_KEY=`cat config/master.key` --add env

source: https://blog.eq8.eu/til/rails-52-credentials-tricks.html

source: https://medium.com/craft-academy/encrypted-credentials-in-ruby-on-rails-9db1f36d8570