If determined, you could circumvent the Steam cryptography ban by providig stenography in 3D graphics to display QR codes calculated in game as polynomials derived from multiple splines hidden (deliberately inefficiently) in computer graphics. Multiple QR codes (that appear in order specifically) then form a pertaining hash, undetected by the game itself and only detected by your other pc or raspberry-pi that takes a photo of them on a camera or webcam (offline).