elliptic-curve: add BasepointTableVartime::lincomb#2405
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Uses `WnafBase::multiscalar_mul` added in RustCrypto/group#14 to provide a variable-time linear combination operation which can use the precomputed wNAF for a basepoint. This has been tested in `p256` where it provides a 25% speedup for ECDSA verification.
tarcieri
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Adds a trait method that can be overridden to plug in variable-time linear combinations using precomputed wNAF for the basepoint which otherwise uses `lincomb_vartime` by default. When used in `p256` in combination with RustCrypto/traits#2405 which added `BasepointTableVartime::lincomb`, this results in a 25% speedup for ECDSA verification: ECDSA/P-256 (SHA-256)/verify time: [146.21 µs 147.14 µs 148.38 µs] change: [−25.356% −24.522% −23.756%] (p = 0.00 < 0.05) Performance has improved. Also applies the optimization to `p384`, `p521`, and `sm2`.
tarcieri
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May 7, 2026
…1759) Adds a trait method that can be overridden to plug in variable-time linear combinations using precomputed wNAF for the basepoint which otherwise uses `lincomb_vartime` by default. When used in `p256` in combination with RustCrypto/traits#2405 which added `BasepointTableVartime::lincomb`, this results in a 25% speedup for ECDSA verification: ECDSA/P-256 (SHA-256)/verify time: [146.21 µs 147.14 µs 148.38 µs] change: [−25.356% −24.522% −23.756%] (p = 0.00 < 0.05) Performance has improved. Also applies the optimization to `p384`, `p521`, and `sm2`.
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Uses
WnafBase::multiscalar_muladded in RustCrypto/group#14 to provide a variable-time linear combination operation which can use the precomputed wNAF for a basepoint.This has been tested in
p256where it provides a 25% speedup for ECDSA verification.