title: Add secret environment variable to Travis CI
body: <p>I'm currently trying to add a secret environment variable to Travis-CI. <a href="http://about.travis-ci.org/docs/user/build-configuration/" rel="nofollow">In the docs</a> ("Secure environment variables") I found the following line to do this:</p>
  
  <pre><code>gem install travis
  travis encrypt -r travis-ci/travis-core MY_SECRET_ENV=super_secret
  </code></pre>
  
  <p>If I understood this correctly I must replace <code>travis-ci/travis-core</code> with the name of my own repository, because the encryption should only be valid for my repository. Therefore, there must be a public key in the repository. Is there a special <code>travis</code> command to add this key? How does this exactly work? Or is this just my ssh public key?</p>
  
  <p>When I run the following command:</p>
  
  <pre><code>travis encrypt -r my_username/my_repo MY_SECRET_ENV=super_secret
  </code></pre>
  
  <p>I get the following error: </p>
  
  <pre><code>There was an error while fetching public key, please check if you entered correct slug
  </code></pre>