diff --git a/book/source/17-zoom_certificates.md b/book/source/17-zoom_certificates.md
index a672861..1aa15a8 100644
--- a/book/source/17-zoom_certificates.md
+++ b/book/source/17-zoom_certificates.md
@@ -353,7 +353,7 @@ The hash digest is calculated from the following data (see [Computing Signatures
 - the serialized primary key's public data
 - the serialized direct key signature packet (excluding the unhashed area)
 
-The signature is derived from this hash digest.
+The signature is calculated from this hash digest.
 
 (zoom_enc_subkey)=
 ## Encryption subkey