diff --git a/book/source/17-zoom_certificates.md b/book/source/17-zoom_certificates.md
index 65051b9..a672861 100644
--- a/book/source/17-zoom_certificates.md
+++ b/book/source/17-zoom_certificates.md
@@ -6,7 +6,7 @@ SPDX-License-Identifier: CC-BY-SA-4.0
 (zoom_certificates)=
 # Zooming in: Packet structure of certificates
 
-Now that we've established the concepts and components that make up OpenPGP certificates , let's look at the internal details of an example certificate.
+Now that we've established the concepts and components that make up OpenPGP certificates, let's look at the internal details of an example certificate.
 
 ## A very minimal OpenPGP certificate
 
@@ -341,19 +341,19 @@ This concludes the unhashed subpacket data.
 
 This next section shows the remaining fields of this signature packet, which relate to the cryptographic digital signature:
 
-- `digest_prefix: 0x6747`: the left 16 bits of the signed hash value
+- `digest_prefix: 0x6747`: the left 16 bits of the signed hash digest
 
 - `salt_len, salt`: a random [salt value](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-10.html#name-advantages-of-salted-signat) with size [matching the hash algorithm](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-10.html#hash-algorithms-registry))
 
 - `ed25519_sig`: [algorithm-specific](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-10.html#name-algorithm-specific-fields-for-ed2) representation of the signature (here: 64 bytes of Ed25519 signature)
 
-The signature's hash is calculated from the following data:
+The hash digest is calculated from the following data (see [Computing Signatures](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-11.html#name-computing-signatures) in the RFC):
 
 - the signature's salt
 - the serialized primary key's public data
 - the serialized direct key signature packet (excluding the unhashed area)
 
-Refer to [Computing Signatures](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-11.html#name-computing-signatures) in the RFC for more details.
+The signature is derived from this hash digest.
 
 (zoom_enc_subkey)=
 ## Encryption subkey
@@ -509,7 +509,7 @@ The rest of the packet mirrors the *Direct Key Signature* discussed above:
 - a salt value 
 - the cryptographic signature itself
 
-The signature is calculated over a hash. In this case, the hash is derived from the following data:
+The signature is calculated over a hash digest. In this case, the hash digest is derived from the following data:
 
 - the signature's salt 
 - the serialized primary key's public data