Docs: Add file-based encryption docs

Bug: 27380276
Change-Id: I26d135e0c87e0441e220edf2f05a6dd066cba6ef
diff --git a/src/security/security_toc.cs b/src/security/security_toc.cs
index 805905c..aa8f0da 100644
--- a/src/security/security_toc.cs
+++ b/src/security/security_toc.cs
@@ -84,9 +84,13 @@
   <li class="nav-section">
     <div class="nav-section-header">
       <a href="<?cs var:toroot ?>security/encryption/index.html">
-        <span class="en">Full Disk Encryption</span>
+        <span class="en">Encryption</span>
       </a>
     </div>
+    <ul>
+      <li><a href="<?cs var:toroot ?>security/encryption/file-based.html">File-Based Encryption</a></li>
+      <li><a href="<?cs var:toroot ?>security/encryption/full-disk.html">Full-Disk Encryption</a></li>
+    </ul>
   </li>
   <li class="nav-section">
     <div class="nav-section-header">