doc: secure boot: Explain output of digest_secure_bootloader command

Mentioned on forum https://esp32.com/viewtopic.php?f=13&t=8162&start=10#p34714

diff --git a/docs/en/security/secure-boot.rst b/docs/en/security/secure-boot.rst
index bec0dbdbf1856e4c66bb0d926958138ae21cfbeb..79baa872554be940845a913a74195dda32da23db 100644 (file)
--- a/docs/en/security/secure-boot.rst
+++ b/docs/en/security/secure-boot.rst
@@ -258,7 +258,9 @@ To generate a bootloader digest::
 
   espsecure.py digest_secure_bootloader --keyfile ./securebootkey.bin --output ./bootloader-digest.bin build/bootloader/bootloader.bin
 
-Keyfile is the 32 byte raw secure boot key for the device. To flash this digest onto the device::
+Keyfile is the 32 byte raw secure boot key for the device.
+
+The output of the ``espsecure.py digest_secure_bootloader`` command is a single file which contains both the digest and the bootloader appended to it. To flash the combined digest plus bootloader to the device::
 
   esptool.py write_flash 0x0 bootloader-digest.bin