Created function to mask SSN in Participant show view. Added to Participant helper.

app/helpers/participants_helper.rb

@@ -1,2 +1,7 @@
 module ParticipantsHelper
+    def mask_ssn(ssn)
+        return '' if ssn.blank?
+    
+        "*****#{ssn[-4..-1]}"
+      end
     end

app/views/participants/show.html.erb

@@ -39,7 +39,7 @@
 
           <p class="card-text">
             <strong>SSN:</strong>
-            <%= @participant.ssn %>
+            <%= mask_ssn(@participant.ssn) %>
           </p>
 
           <p class="card-text">