[crypto] Harden RSA modexp subroutine. #25694
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Add some SCA hardening measures to the modexp subroutine that selects either the squared or squared-and-multiplied result in square-and-multiply-always modular exponentiation. Although the rest of the code is not hardened, the hardening for RSA will likely preserve this subroutine, so hardening it is still useful. Signed-off-by: Jade Philipoom <[email protected]>
jadephilipoom
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CherryPick:earlgrey_1.0.0
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Performance impact is minimal: RSA-2048 modexp goes from |
johannheyszl
approved these changes
Dec 18, 2024
nasahlpa
approved these changes
Dec 18, 2024
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Thanks, LGTM!
This is the code snippet that was used for the SCA analysis @johannheyszl?
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@nasahlpa this is correct |
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See #25300 for context; this is an updated version of that hardening change based on the coding guidelines from COCO-Alma.
Add some SCA hardening measures to the modexp subroutine that selects either the squared or squared-and-multiplied result in square-and-multiply-always modular exponentiation.
Although the rest of the code is not hardened, the hardening for RSA will likely preserve this subroutine, so hardening it is still useful.