title: What is the use of secret_key_base in rails 4
body: <p>I am new to Rails 4, and do not understand the use of <code>secret_key_base</code> under <code>config/secrets.yml</code> in Rails 4. Can you please explain this concept?</p>
  
  <p>Also, when I am working in the production environment, I am prompted to set the <code>secret_key</code> with <code>devise.rb</code>, <code>config.secret_key</code>, and <code>secret_key_base</code>. However, I can generate a new secret using the <code>rake secret</code> command. </p>
  
  <p>What is the difference between development and production environments?</p>
  
  <p>How is it matching the newly generated <code>secret_key</code> when I add it with <code>secret_key_base</code> every time I generate?</p>
  
  <p>How is it securing the application with other servers?</p>