diff --git a/docs/encrypted_images.md b/docs/encrypted_images.md
index 834428f..85d26d8 100644
--- a/docs/encrypted_images.md
+++ b/docs/encrypted_images.md
@@ -120,12 +120,14 @@
 image being determined, the upgrade consists in reading the blocks from
 the `secondary slot`, decrypting and writing to the `primary slot`.
 
-If swap is used for the upgrade process, the encryption happens when
-copying the sectors of the `secondary slot` to the scratch area.
-
-The `scratch` area is not encrypted, so it must reside in the internal
-flash of the MCU to avoid attacks that could interrupt the upgrade and
-dump the data.
+If swap using scratch is used for the upgrade process, the decryption happens
+when copying the content of the scratch area to the `primary slot`, which means
+the scratch area does not contain the image unencrypted. However, unless
+`MCUBOOT_SWAP_SAVE_ENCTLV` is enabled, the decryption keys are stored in
+plaintext in the scratch area. Therefore, `MCUBOOT_SWAP_SAVE_ENCTLV` must be
+enabled if the scratch area does not reside in the internal flash memory of the
+MCU, to avoid attacks that could interrupt the upgrade and read the plaintext
+decryption keys from external flash memory.
 
 Also when swap is used, the image in the `primary slot` is checked for
 presence of the `ENCRYPTED` flag and the key TLV. If those are present the