Message Signature Validation

[Pivotal Issue 78632442][1]

[1]: https://www.pivotaltracker.com/n/projects/1163646/stories/78632442
certifiable
[sur-tuh-fahy-uh-buh l, sur-tuh-fahy-]  
adjective
1. capable of being certified.

That was the intent I used here :wink: