doc: imx: hab: Reorganize High Assurance Boot documentation

The current High Assurance Boot document README.mxc_hab
include details for the following features in a single file:

- HAB Secure Boot
- HAB Encrypted Boot

Split HAB documentation in a specific directory for a cleaner
documentation structure, subsequent patches will include more
content in HAB documentation.

Signed-off-by: Breno Lima <breno.lima@nxp.com>

1 files changed, 43 insertions, 0 deletions

diff --git a/doc/imx/hab/habv4/encrypted_boot.txt b/doc/imx/hab/habv4/encrypted_boot.txt
new file mode 100644
index 0000000000..c59d204d38
--- /dev/null
+++ b/doc/imx/hab/habv4/encrypted_boot.txt
@@ -0,0 +1,43 @@
+1. Setup U-Boot Image for Encrypted Boot
+----------------------------------------
+An authenticated U-Boot image is used as starting point for
+Encrypted Boot. The image is encrypted by i.MX Code Signing
+Tool (CST). The CST replaces only the image data of
+u-boot-dtb.imx with the encrypted data. The Initial Vector Table,
+DCD, and Boot data, remains in plaintext.
+
+The image data is encrypted with a Encryption Key (DEK).
+Therefore, this key is needed to decrypt the data during the
+booting process. The DEK is protected by wrapping it in a Blob,
+which needs to be appended to the U-Boot image and specified in
+the CSF file.
+
+The DEK blob is generated by an authenticated U-Boot image with
+the dek_blob cmd enabled. The image used for DEK blob generation
+needs to have the following configurations enabled in Kconfig:
+
+CONFIG_SECURE_BOOT=y
+CONFIG_CMD_DEKBLOB=y
+
+Note: The encrypted boot feature is only supported by HABv4 or
+greater.
+
+The dek_blob command then can be used to generate the DEK blob of
+a DEK previously loaded in memory. The command is used as follows:
+
+dek_blob <DEK address> <Output Address> <Key Size in Bits>
+example: dek_blob 0x10800000 0x10801000 192
+
+The resulting DEK blob then is used to construct the encrypted
+U-Boot image. Note that the blob needs to be transferred back
+to the host.Then the following commands are used to construct
+the final image.
+
+cat u-boot-dtb.imx csf-u-boot.bin > u-boot-signed.imx
+objcopy -I binary -O binary --pad-to <blob_dst> --gap-fill=0x00 \
+    u-boot-signed.imx u-boot-signed-pad.bin
+cat u-boot-signed-pad.imx DEK_blob.bin > u-boot-encrypted.imx
+
+    NOTE: u-boot-signed.bin needs to be padded to the value
+    equivalent to the address in which the DEK blob is specified
+    in the CSF.