diff --git a/book/source/03-cryptography.md b/book/source/03-cryptography.md
index 58a942a..363e936 100644
--- a/book/source/03-cryptography.md
+++ b/book/source/03-cryptography.md
@@ -62,7 +62,7 @@ Unlike symmetric cryptography, public-key cryptography doesn't require participa
 
 In many places, we'll deal with asymmetric cryptographic key pairs:
 
-```{figure} diag/cryptographic_keypair.svg
+```{figure} diag/cryptographic_keypair.png
 ---
 ---
 An asymmetric cryptographic key pair
diff --git a/book/source/04-certificates.md b/book/source/04-certificates.md
index e4c587b..9e5bf74 100644
--- a/book/source/04-certificates.md
+++ b/book/source/04-certificates.md
@@ -32,7 +32,7 @@ An OpenPGP certificate (or "OpenPGP key") is a collection of an arbitrary number
 
 We sometimes collectively refer to component keys and identity information as the "components" of a certificate.
 
-```{figure} diag/OpenPGP_Certificate.svg
+```{figure} diag/OpenPGP_Certificate.png
 
 Typical components in an OpenPGP certificate
 ```
@@ -60,7 +60,7 @@ Component key representations that include private key material also contain met
 
 For each OpenPGP component key, an *OpenPGP fingerprint* can be derived from the combination of the public key material and creation timestamp (plus additional algorithm parameters, in the case of [ECDH Keys](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-10.html#name-algorithm-specific-part-for-ecd)):
 
-```{figure} diag/Fingerprint.svg
+```{figure} diag/Fingerprint.png
 
 Every OpenPGP component key can be named by a fingerprint
 ```