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authorRaul Cardenas <>2015-02-27 11:22:06 -0600
committerStefano Babic <>2015-03-02 09:57:06 +0100
commit0200020bc2b8192c31dc57c600865267f51bface (patch)
tree77e47e958773096b7cb53c20a0c6a1f4d83e46d8 /doc
parentb5cd10b911f632f74e1211ef786989781d2a1ca1 (diff)
imx6: Added DEK blob generator command
Freescale's SEC block has built-in Data Encryption Key(DEK) Blob Protocol which provides a method for protecting a DEK for non-secure memory storage. SEC block protects data in a data structure called a Secret Key Blob, which provides both confidentiality and integrity protection. Every time the blob encapsulation is executed, a AES-256 key is randomly generated to encrypt the DEK. This key is encrypted with the OTP Secret key from SoC. The resulting blob consists of the encrypted AES-256 key, the encrypted DEK, and a 16-bit MAC. During decapsulation, the reverse process is performed to get back the original DEK. A caveat to the blob decapsulation process, is that the DEK is decrypted in secure-memory and can only be read by FSL SEC HW. The DEK is used to decrypt data during encrypted boot. Commands added -------------- dek_blob - encapsulating DEK as a cryptgraphic blob Commands Syntax --------------- dek_blob src dst len Encapsulate and create blob of a len-bits DEK at address src and store the result at address dst. Signed-off-by: Raul Cardenas <> Signed-off-by: Nitin Garg <> Signed-off-by: Ulises Cardenas <> Signed-off-by: Ulises Cardenas-B45798 <>
Diffstat (limited to 'doc')
1 files changed, 48 insertions, 0 deletions
diff --git a/doc/README.mxc_hab b/doc/README.mxc_hab
index 43e64a2797..e9340dd14c 100644
--- a/doc/README.mxc_hab
+++ b/doc/README.mxc_hab
@@ -46,3 +46,51 @@ cat u-boot.imx U-Boot_CSF_pad.bin > u-boot-signed.imx
NOTE: U-Boot_CSF.bin needs to be padded to the value specified in
the imximage.cfg file.
+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 Freescale's Code
+Signing Tool (CST). The CST replaces only the image data of
+u-boot.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:
+Note: The encrypted boot feature is only supported by HABv4 or
+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.
+objcopy -I binary -O binary --pad-to 0x2000 --gap-fill=0x00 \
+ U-Boot_CSF.bin U-Boot_CSF_pad.bin
+cat u-boot.imx U-Boot_CSF_pad.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.
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