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A big part of the RISC-V story is the idea that microarchitecture decisions belong to the implementation and not the ISA specification. Specifying that multipli
by 0xcde4c3db 7y ago
A big part of the RISC-V story is the idea that microarchitecture decisions belong to the implementation and not the ISA specification. Specifying that multiplication must be constant-time would effectively be specifying that area-optimized cores aren't allowed to provide the multiplication instructions.
- anoncake 7y agoCouldn't this be solved by having constant-time and regular multiplication instructions?
- 0xcde4c3db 7y agoSure, but the constant-time instructions would presumably be defined in an extension along with other constant-time or crypto-optimized instructions.
- justincormack 7y agoArm 8.4 has a constant time flag that makes most instructions constant time, without changing the instruction set. You could definitely add this to risc-v. Or just make a constant time implementation.