Sig­nal

A WHISTLE­BLOWER’S FAVOURITE Free | www.whis­per­sys­tems.org

TechLife Australia - - DIS­COVER -

SIG­NAL IS PER­HAPS the holy grail of en­crypted chat ap­pli­ca­tions — and if you don’t be­lieve us, then take Ed­ward Snow­den’s word for it. It’s a free, open-source plat­form from Open Whis­per Sys­tems that’s been en­dorsed by the likes of se­cu­rity tech­nol­o­gist Bruce Sch­neier and Laura Poitras, an Os­car-win­ning film­maker and jour­nal­ist. It’s easy to use and can re­place the de­fault SMS mes­sag­ing app on your smart­phone. And via a Chrome ex­ten­sion, it’s even avail­able to use on your desk­top.

Sig­nal’s selling point is the at­ten­tion it pays to user pri­vacy. The source code is avail­able to the pub­lic on GitHub, so it can be in­de­pen­dently au­dited any time, some­thing a Ger­man team did for Sig­nal’s Tex­tSe­cure pro­to­col and gave it the thumbs-up.

Down­load the app, en­ter your mo­bile num­ber and you’ll be sent a key pair. This is used to ver­ify the iden­tity of other users you’re com­mu­ni­cat­ing with. With ac­cess to your phone book, the app will list the con­tacts al­ready us­ing Sig­nal and you’re good to go... although un­less you hang around in hacker cir­cles, chances are high that none of your friends or fam­ily use the app.

Sig­nal sends text via data, sup­ports voice and video calls, and has a con­ve­nient group mes­sag­ing func­tion. When com­mu­ni­cat­ing with other Sig­nal users, mes­sages are au­to­mat­i­cally en­crypted, but when tex­ting non-Sig­nal users, you can ei­ther in­vite them to try the app or send an un­en­crypted reg­u­lar SMS. Sim­i­larly, if you call an­other Sig­nal user, the call is en­crypted and routed over the in­ter­net, much like a Skype call. If the re­cip­i­ent of your call is a non-Sig­nal user, the app feeds the con­tact num­ber into your phone’s reg­u­lar di­aler for a nor­mal, un­en­crypted con­ver­sa­tion.

All mes­sages sent via Sig­nal are en­crypted and de­crypted on the user’s phone, mak­ing them hard to in­ter­cept in tran­sit. Mes­sages are en­crypted us­ing a Curve25519 key, so that if texts are com­pro­mised, the at­tacker can ac­cess only part of the mes­sage. Sig­nal con­ver­sa­tions also have unique ‘safety num­bers’ to ver­ify con­tact iden­ti­ties — use­ful if you’re not 100% sure who’s at the other end.

This is a great lit­tle mes­sag­ing app (with or with­out the beefed-up se­cu­rity) — the main prob­lem will likely be con­vinc­ing your con­tacts to get started on Sig­nal.

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