Does crypto/AES work on hardware that doesn't have the aes instruction set? Hello, Will crypto/aes, cipher/GCM work on hardware without embedded aes support?

[Sean]

Hello,

Will **crypto/aes**, **cipher/GCM** work on hardware without embedded aes support?

What I want to know is how these packages respond in cases where there is no embedded AES support (fast is not important).

[Matthew Walster]

Sure, it's enabled in a build constraint:

https://cs.opensource.google/go/go/+/refs/tags/go1.17.3:src/crypto/aes/cipher_asm.go

It's not an exact science, there's no testing for the instruction afaict, it's just that anything running the amd64 architecture has the aesni instructions. I assume likewise for arm64.

M

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[Matthew Walster]

Whoops, yes, there is a feature flag there I missed "supportsAES" etc. It appears to be gated on that instruction being present, at which time the operation becomes roughly constant time.

M