you ask for cross-platform and you don't define "most secure". so it seems like the "right" answer is the one that is believed to be secure and is as cross-pla

you ask for cross-platform and you don't define "most secure". so it seems like the "right" answer is the one that is believed to be secure and is as cross-platform as possible. and i think that would be openssl. it's famous for causing bugs/weaknesses from being used incorrectly, but afaik it's secure if used correctly. and it compiles on a wide range of hardware.