Add documentation on how Android encryption works.

Change-Id: I20f55eca5e6043e0d8dd3eef4d3f17f5587c56af
diff --git a/src/tech/index.md b/src/tech/index.md
index a0cc0f8..cdcaac0 100644
--- a/src/tech/index.md
+++ b/src/tech/index.md
@@ -48,3 +48,11 @@
 
 [» NFC Information](/tech/nfc/index.html)
 
+## Encryption Technical Information ##
+The Android Open-Source Project includes the ability to encrypt the user's data.
+This document is written for 3rd parties developing Android devices who want to
+include support for encryption on their device.  It covers the few things that
+must be done so encryption will work.
+
+[» Encryption Information](/tech/encryption/index.html)
+