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by datadeft 812 days ago
It is bad, it is required for performance reasons.

The questions is what could be the solution going forward, which is going to be a huge change anyway. I do not see a way out of this with our current architectures.

1 comments

Neither block ciphers, nor stream ciphers, nor common public key algorithms (RSA, Ed25519) need or even profit from this. They just need fast access to the register-register math, maybe loop sequentially through all members of a fixed sized array a fixed number of times. The only thing those implementing such algorithms would probably like having is a few kiB of safe to access scratchpad memory for code and data. On entry to the crypto code copy the code and data there, enable a constant time mode for compute instructions and run the algorithm at full speed without worrying.