The feds can insist. You might go to jail for 10 years
You are using Whatsapp because you like to know your communication with your friends is strictly private and cannot be intercepted? As it is encrypted, you are safe? The government told you they've given up trying to get backdoors into secure apps. And anything else in any other kinds if devices. On your PC you have the best firewall and AV and your PGP keeps things safe. No one can get in and least of course the pesky government spies and Dutton's servants.
Fail. Do not pass GO. Do not collect $200.
Everyone's friend Peter Dutton
The government has introduced The Assistance and Access Bill 2018 for "consultation" (bullshit) and you've got three weeks to express your views about that by emailing AssistanceBill.Consultation@homeaffairs.gov.au. Read all about it here and here and here.
Basically it means the Dutton's servants, ASIO, feds, police and just about every Tom, Dick and Harry that calls himself "law enforcement" will be able to read your messages before you send them and after you receive replies. It will be able to hack your phone and any device, make changes, spy, download stuff and upload hacking tools and even follow you on GPS. How? By asking foreign and domestic communications providers, device manufacturers, component manufacturers, application providers, and traditional telecommunications carriers and carriage service providers. And if anyone does not comply, well they'll fine you 10 million and then you will still have to modify/create anything they ask of you so that unimpeded access to your stuff is possible. And if anyone tells anyone what's happening, well they're down the shit creek too. You of course will be totally unaware anything has happened.
What? You have nothing to hide, huh? Ah well that's OK then. As long as we have honest government, coppers and spies, you'll be safe, but it has amply been demonstrated over the years there are crooks and abusers in all agencies and at all levels of government. Just how sure are you they you were not targeted by mistake? Or you were targeted by some bad people or person? Well, you'll never know what hit you when they come to take you away.
What can you do? The pollies won't do much except maybe for the Greens or some independents, but as usual Labor will help the libs to slide the new laws through the parliament, no worries. Get on to you local member. Complain, warn him you won't vote for him and neither will your mum or her dogs and cats. There's strength in numbers!
Alternatively, just sit back like most Australians and do nothing and if some agency in the USA acting on some new law brought on by that nutjob Trump wants to get you arrested, well that can be done too under the new law. In other words, you are also subject to arrest and prosecution under some criminal law in some foreign country. And if you refuse to unlock your phone for the feds, then off you go to jail for 10 years.