crypto: Restrict conjugate() to degree-2 extension fields#1485
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crypto: Restrict conjugate() to degree-2 extension fields#1485
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The conjugate operation (negating the second coefficient) is only mathematically correct for degree-2 extensions. Add a requires clause to prevent misuse on degree-3+ types where it would produce incorrect results silently.
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Pull request overview
This PR prevents mathematically incorrect use of ExtFieldElem::conjugate() by restricting it to quadratic (degree-2) extension fields, where conjugation is defined as negating the second coefficient.
Changes:
- Add a C++20
requires(DEGREE == 2)constraint toExtFieldElem::conjugate(). - Simplify the conjugation implementation to directly return
(a, -b)for degree-2 elements. - Update the doc comment to explicitly document the degree-2 semantics.
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## master #1485 +/- ##
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- Coverage 96.74% 96.74% -0.01%
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Files 156 156
Lines 14166 14163 -3
Branches 3337 3336 -1
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- Hits 13705 13702 -3
Misses 317 317
Partials 144 144
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rodiazet
approved these changes
Apr 14, 2026
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The conjugate operation (negating the second coefficient) is only mathematically correct for degree-2 extensions. Add a requires clause to prevent misuse on degree-3+ types where it would produce incorrect results silently.