title: Determine publisher of SNS message?
body: <p>Is there a standard mechanism an SNS subscriber could use to verify the identity of the publisher?</p>
  
  <p>My scenario is that several IAM roles and users are allowed to publish to an SNS topic and I want the subscribers to know which one published it. </p>
  
  <p>I know I could use a topic per publisher or have publishers sign each message but I’d prefer a single SNS topic and not require the publishers to do more than just publishing a message. </p>