China’s plan to introduce a nationwide digital identification system has been met with criticism of government overreach in a country that already closely monitors and censors speech.

Some legal experts and users on the world’s largest internet market have openly doubted the efforts’ stated goal of protecting privacy after authorities published the proposal last week.

China’s internet regulator and police said users could opt in to such digital IDs, which would let them verify their identity online without giving up unnecessary personal details to internet service providers.