[rom_ext] Update RSA terms in rom_ext mainfest doc
This enhances some terminolgy with respect to the
signing scheme, mainly regarding the RSA related
portions.
Signed-off-by: Felix Miller <felix.miller@gi-de.com>
diff --git a/sw/device/rom_exts/manifest.md b/sw/device/rom_exts/manifest.md
index 45c4748..bb1b839 100644
--- a/sw/device/rom_exts/manifest.md
+++ b/sw/device/rom_exts/manifest.md
@@ -28,7 +28,7 @@
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Signature Algorithm Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Signature Exponent |
+| Signature Key Public Exponent |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
@@ -49,7 +49,7 @@
| |
+ +
| |
-+ Signature Public Key (3072 bits) +
++ Signature Key Modulus (3072 bits) +
| |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ break ~~~~~~~~~~~~~~~~~~~~~~~~~~~
| |
@@ -103,12 +103,12 @@
**Open Q**: The ordering below is still subject to alignment requirements
for different fields, and may change in future.
-* The `Image Signature`, `ROM_EXT Signature Public Key` and `Image` are not
+* The `Image Signature`, `ROM_EXT Signature Key Modulus` and `Image` are not
shown to scale. This is denoted using `~~~ break ~~~` lines, which specify a
truncation of field size displayed in the diagram, not that a new field has
started.
- * The Signature and Public Key are each 3072 bits long (they are
+ * The Signature and Modulus are each 3072 bits long (they are
notionally `int32_t[96]`s).
* The Code Image itself is variable length, where the length of the entire
@@ -132,11 +132,12 @@
This is used by any ROM_EXT image parsers to identify a ROM_EXT image.
-1. **Image Signature** This is a RSA 3k signature of all the fields that follow
- the signature. This is a sequence of 32-bit values. The signed area of the
- image starts immediately after this field, and runs to the end of the image
- (as defined by the image length). All content outside that range is unsigned
- (including the Manifest Identifier, and the Image Signature itself).
+1. **Image Signature** This is a RSA-3072 signature of the hash of all the
+ fields that follow the signature. This is a sequence of 32-bit values. The
+ signed area of the image starts immediately after this field, and runs to
+ the end of the image (as defined by the image length). All content outside
+ that range is unsigned (including the Manifest Identifier, and the Image
+ Signature itself).
This is used by the Mask ROM during secure boot to validate that a ROM_EXT
image has been produced by a Silicon Creator for this chip. This is also
@@ -182,13 +183,13 @@
* SHA2-512
The specific signature scheme is as yet undefined, but will be based on
- RSA-3k, and one of the message digest algorithms above.
+ RSA-3072, and one of the message digest algorithms above.
-1. **Signature Exponent** This is the RSA exponent to be used during the RSA
- 3K Signature Scheme. This is a 32-bit numeric value.
+1. **Signature Key Public Exponent** This is the RSA public exponent to be used
+ during signature verification. This is a 32-bit numeric value.
- This is used when signing and validating the image. This happens in the
- Mask ROM, as well as during firmware update.
+ This is used when validating the image. This happens in the Mask ROM, as
+ well as during firmware update.
1. **Usage Constraint** This is a 256-bit unsigned numeric value.
@@ -216,8 +217,9 @@
currently tight for space, so this may turn into an Offset to later in the
image.
-1. **Signature Public Key** This is a RSA 3k public key, as used by the image
- signature. This is a sequence of 32-bit values.
+1. **Signature Key Modulus** This is a RSA-3072 modulus, used in both the
+ signing and signature verification operations. This is a sequence of 32-bit
+ values.
This is used when signing and validating the image. This happens in the
Mask ROM, as well as during firmware update.
@@ -313,10 +315,10 @@
**Signature Algorithm Identifier**: TBC
-**Signature Exponent**: TBC
+**Signature Key Public Exponent**: TBC
-**Signature Key Pair**: TBC. We will create a dummy key pair for development,
-but this will not be used in production software.
+**Development Signature Key Pair**: TBC. We will create a dummy key pair for
+development, but this will not be used in production software.
**Extension Allocation**:
