diff --git a/book/source/07-signing_data.md b/book/source/07-signing_data.md
new file mode 100644
index 0000000..94753b5
--- /dev/null
+++ b/book/source/07-signing_data.md
@@ -0,0 +1,2 @@
+(signing_data)=
+# Signatures over data
diff --git a/book/source/07-signature_internals.md b/book/source/08-signature_internals.md
similarity index 100%
rename from book/source/07-signature_internals.md
rename to book/source/08-signature_internals.md
diff --git a/book/source/08-verification.md b/book/source/09-verification.md
similarity index 100%
rename from book/source/08-verification.md
rename to book/source/09-verification.md
diff --git a/book/source/09-encryption.md b/book/source/10-encryption.md
similarity index 100%
rename from book/source/09-encryption.md
rename to book/source/10-encryption.md
diff --git a/book/source/10-decryption.md b/book/source/11-decryption.md
similarity index 100%
rename from book/source/10-decryption.md
rename to book/source/11-decryption.md
diff --git a/book/source/11-armor.md b/book/source/12-armor.md
similarity index 100%
rename from book/source/11-armor.md
rename to book/source/12-armor.md
diff --git a/book/source/12-pitfalls.md b/book/source/13-pitfalls.md
similarity index 100%
rename from book/source/12-pitfalls.md
rename to book/source/13-pitfalls.md
diff --git a/book/source/13-policy.md b/book/source/14-policy.md
similarity index 100%
rename from book/source/13-policy.md
rename to book/source/14-policy.md
diff --git a/book/source/14-resources.md b/book/source/15-resources.md
similarity index 100%
rename from book/source/14-resources.md
rename to book/source/15-resources.md
diff --git a/book/source/15-glossary.md b/book/source/16-glossary.md
similarity index 100%
rename from book/source/15-glossary.md
rename to book/source/16-glossary.md
diff --git a/book/source/16-acknowledgements.md b/book/source/17-acknowledgements.md
similarity index 100%
rename from book/source/16-acknowledgements.md
rename to book/source/17-acknowledgements.md