Surveillance-savvy Hong Kong protesters go digitally dark

Hong Kong's tech-savvy protesters are going digitally dark as they try to avoid surveillance and potential future prosecutions, disabling location tracking on their phones, buying train tickets with cash and purging their social media conversations.

Police used rubber bullets and tear gas to break up crowds opposed to a China extradition law on Wednesday, in the worst unrest the city has witnessed in decades.

Many of those on the streets are predominantly young and have grown up in a digital world, but they are all too aware of the dangers of surveillance and leaving online footprints.

Ben, a masked office worker at the protests, said he feared the extradition law would have a devastating impact on freedoms.

"Even if we're not doing anything drastic -- as simple as saying something online about China -- because of such surveillance they might catch us," the 25-year-old said.

This week groups of demonstrators donned masks, goggles, helmets and caps -- both to protect themselves against