5 ms·

Wouldn't they be saved to memory anyway on a context switch?

• Klasiaster 7y ago
  Yes, but I thought this is done in kernel space and a userspace attack has no access to that while the syscall is served.
  • Liquid_Fire 7y ago
    That is true - it's probably more secure than storing them in the process, but several of these side-channel attacks can apply to kernel space (depending on hardware and security patches applied). It's also not portable - OpenSSH runs on non-x86 architectures, and they might not have spare basically unused registers lying around. Finally, I'm not sure the x87 registers have enough space to fit these keys. You have 8 80-bit registers, for a total of 640 bits. Your typical SSH private key might be 2048 bits or more. So it's a fun and creative line of thinking, but probably not practical in this case.