diff --git a/ch04_keys.adoc b/ch04_keys.adoc
index 0a25e545..b5c1aa12 100644
--- a/ch04_keys.adoc
+++ b/ch04_keys.adoc
@@ -28,7 +28,7 @@ the addresses used by modern Bitcoin software.
 
 === Public Key Cryptography
 
-Public key
+Public ((("public key cryptography", id="pub-key")))key
 cryptography was invented in the 1970s and is a mathematical foundation
 for modern computer and information security.
 
@@ -66,7 +66,7 @@ pairs, each consisting of a private key and a public key. The private
 key (k) is a number, usually derived from a number picked at random.
 From the private key, we
 use elliptic curve multiplication, a one-way cryptographic function, to
-generate a public key (K).
+generate a public((("public key cryptography", startref="pub-key"))) key (K).
 
 .Why Use Asymmetric Cryptography (Public/Private Keys)?
 ****