NVENC SDK question.

Hi all,
Can someone tell me how to avoid NV_ENC_ERR_INCOMPATIBLE_CLIENT_KEY in nvEncOpenEncodeSession ? I have 660Ti and as far as I understood from description HW NVENC will not work on this card, but according to this topic [url]Where can I get GTX 680 NVENC SDK ? - CUDA Programming and Performance - NVIDIA Developer Forums the key may be granted and directly provided to encoder. I wonder if it’s true and what are the limitations of the trial version of the key ?