blindsign/blindrsa: reject non-canonical signatures. - #615
Merged
Conversation
The blind RSA verifier accepts signatures that are larger than the modulus (but have the same length). In Privacy Pass, this could allow double spending if both the signature and nonce are used for double spend prevention. Using only the nonce is sufficient to prevent this.
bwesterb
approved these changes
Jun 2, 2026
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
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
The blind RSA verifier accepts signatures that are larger than the modulus (but have the same length). In Privacy Pass, this could allow double spending if both the signature and nonce are used for double spend prevention. Using only the nonce is sufficient to prevent this.