diff --git a/book/source/03-highlevel.md b/book/source/02-highlevel.md
similarity index 100%
rename from book/source/03-highlevel.md
rename to book/source/02-highlevel.md
diff --git a/book/source/03-cryptography.md b/book/source/03-cryptography.md
new file mode 100644
index 0000000..2e3ad50
--- /dev/null
+++ b/book/source/03-cryptography.md
@@ -0,0 +1,5 @@
+# Cryptographic concepts/terms
+
+```
+Lars suggests that we should have a place where we introduce cryptographic terms that we use, and give short definitions (without getting into how specific algorithms work)
+```
\ No newline at end of file
diff --git a/book/source/index.rst b/book/source/index.rst
index 13b1dde..200b187 100644
--- a/book/source/index.rst
+++ b/book/source/index.rst
@@ -6,7 +6,8 @@ Notes on OpenPGP
    :maxdepth: 3
 
    01-intro.md
-   03-highlevel.md
+   02-highlevel.md
+   03-cryptography.md
    04-certs.md
    05-private.md
    06-signatures.md