Update EIP-4788: Move to Prime Modulus #7
Merged
Conversation
This file contains 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
lightclient
approved these changes
Sep 12, 2023
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
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Outdated suggestions cannot be applied.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.
See ethereum#7672 (comment).
HISTORY_BUFFER_LENGTHdetermines the overall size of the history region of the 4788 contract in storage. Both current proposed modulus, as well as the replacement proposed in the branch this PR is against, share prime factors with the current slot time (12s). This means that the usage of the history region will be sparse (only 1/12 of the storage slots in the region will be used). Furthermore, if we change the slot time in the future, this will change in somewhat arbitrary ways (depending on how many factors the new slot time and the modulus share). While this does not affect the functioning of the EIP, it does add unnecessary variance to two aspects, namely the total storage requirements and the total history depth available.This PR changes the modulus to a prime number, so that there can never be any shared factors with the slot time. This way, 100% of the history region will be utilized, allowing for simple reasoning about total storage requirements and the total history depth, even in the case of future slot time changes. The specific value (
8191 == 2**13 - 1) was chosen so that in the 12s slot time case it matches the total history depth of the original modulus as closely as possible.