Fix underconstrained sign
function.
#84
Merged
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Outdated suggestions cannot be applied.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.
Description
The
sign
function inmaingate
returns the parity of a field element.In order to do this for an element
x
it exhibits thatx = 2 * k + sign
. Where sign is 0 or 1 andk
is an auxiliary witness.However,
k
needs to be range checked so that this equation doesn't wrap around, inverting the sign.Note: It would be great to find a way to implement this function without the need for range checks, but I haven't been able to do so.
Any suggestions in this direction are greatly appreciated.
Changes
sign
has been moved frommaingate
tointeger