title: ssh-rsa public key validation using a regular expression
body: <p>What regular expression can I use (if any) to validate that a given string is a legal ssh rsa public key?</p>
  
  <p>I only need to validate the actual key - I don't care about the key type the precedes it or the username comment after it.</p>
  
  <p>Ideally, someone will also provide the python code to run the regex validation.</p>
  
  <p>Thanks.</p>