* mpi/mpi-pow.c (USE_ALGORITHM_SIMPLE_EXPONENTIATION): New.
(mul_mod) [!USE_ALGORITHM_SIMPLE_EXPONENTIATION]: New.
(mpi_powm) [!USE_ALGORITHM_SIMPLE_EXPONENTIATION]: New implementation
of left-to-right k-ary exponentiation.
--
This is a backport from Libgcrypt commit
45aa6131e93fac89d46733b3436d960f35fb99b2
Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>
For the Yarom/Falkner flush+reload cache side-channel attack, we
changed the code so that it always calls the multiplication
routine (even if we can skip it to get result). This results some
performance regression.
This change is for recovering performance with efficient
algorithm.
Signed-off-by: Werner Koch <wk@gnupg.org>