diff --git a/ch13_security.adoc b/ch13_security.adoc
index 35f34ed9..e43dcb65 100644
--- a/ch13_security.adoc
+++ b/ch13_security.adoc
@@ -20,7 +20,7 @@ need to think about securing our bitcoins in a novel way too.
 
 === Security Principles
 
-The core principle in Bitcoin is
+The ((("Bitcoin", "security", "principles of", id="bitcoin-security-principle")))((("security", "principles of", id="security-principle")))core principle in Bitcoin is
 decentralization and it has important implications for security. A
 centralized model, such as a traditional bank or payment network,
 depends on access control and vetting to keep bad actors out of the
@@ -140,7 +140,7 @@ this point because their security architecture and design fails even
 under the most casual scrutiny. These centralized implementations had
 invested trust explicitly in numerous components outside the Bitcoin
 blockchain, such as hot wallets, centralized databases,
-vulnerable encryption keys, and similar schemes.
+vulnerable encryption keys, and ((("Bitcoin", "security", "principles of", startref="bitcoin-security-principle")))((("security", "principles of", startref="security-principle")))similar schemes.
 
 === User Security Best Practices