This gem lets you encrypt fields in your Rails app's database, and by default, raise an exception if you try to access any of the fields, until you call the prompt method which will ask for the encryption key.

gem 'encryption_activator'

EncryptionActivator.key     # raises EncryptionActivator::KeyNotSetException
EncryptionActivator.prompt  # prompts for key at the terminal
EncryptionActivator.key     # => returns key

Put this in eg. config/initializers/activerecord_attr_encrypted.rb :

ActiveRecord::Base.attr_encrypted_options.merge!(
  key:    EncryptionActivator.keyproc,
  encode: true
)

Your app will work without the key being set, as long as you don't try to read any of the encrypted fields.

Somewhere in your worker process or startup thread, you call this:

EncryptionActivator.prompt

After this, the app can read and write the encrypted fields.

OR you can use the environment variable ENCRYPTION_ACTIVATOR_KEY