Update rom_ctrl scrambling logic
#90
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
rivos-eblot
reviewed
Dec 17, 2024
AlexJones0
force-pushed
the
rom_updates
branch
from
c1e7f50 to
27c4fca
Compare
For Earlgrey, the number of PRINCE cipher half rounds was increased from 2 to 3 (5 effective rounds to 7 effective rounds, including the substitution perm rounds). This was added for improved security, and requires a simple constant change.
In Earlgrey, the S&P layer has been removed from the data scrambling logic, which affects the scrambling of the generated ROM. The functionality is removed entirely from the ROM Control to improve error detection guarantees, interactions with ECC, and timing. This commit removes the now-redundant logic related to the S&P layer, instead directly unscrambling words by XORing the keystream and the `scr`/`in` data.
AlexJones0
force-pushed
the
rom_updates
branch
from
27c4fca to
851b941
Compare
rivos-eblot
approved these changes
Dec 18, 2024
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This PR updates the ROM Control to match Earlgrey's latest functionality. See the commit messages for more details.
This PR also contains a commit to updatepyot.py, to allow for the use of aliases in test-specific configuration values. Please let me know if there's already a way to do this - it didn't seem to be working for me, and I've found it a useful feature for e.g. using a specific ROM for a specific test.This has been tested against the test
kmac_app_rom_test_fpga_cw310_rom_with_fake_keys, using the builtmask_rom_fpga_cw310.39.scr.vmemproduced by the test, which was failing previously, but now passes. The test and mask ROM were built from master on OpenTitan.