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Add note about branchless shift being cryptographically preferable

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mratsim 2018-02-16 17:02:09 +01:00
parent 5886d76ebc
commit f044d8a476
1 changed files with 3 additions and 0 deletions
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src/uint_bitwise_ops.nim
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@ -74,6 +74,9 @@ proc `shr`*[T: MpUint](x: T, y: SomeInteger): T {.noInit, noSideEffect.}=
#
# Quick testing on MpUint[uint32] on x86_64 with Clang shows that it is somewhat slower
# Fast shifting is key to fast division and modulo operations
#
# Note: Using branchless shift will help preventing timing attacks / be more robust cryptography-wise
# Note2: It's a mess to maintain/read/update
# proc `shl`*[T: MpUint](x: T, y: SomeInteger): T {.noInit, noSideEffect.}=
# ## Compute the `shift left` operation of x and y