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Encrypted Phone Calls with Ostel

Encrypted Phone Calls with Ostel


Ostel is tool funded by the Guardian Project for having end-to-end encrypted phone calls. Their stated goal for Ostel is to promote the use of free, open protocols, standards and software, to power end-to-end secure voice communications on mobile devices, as well as with desktop computers. It is available for Android, iPhone & iPad, Mac, Windows, Linux and Blackberry. Ostel is open source.

Ostel is not free for iPhone & iPad. In fact it It’s a one time paid app for $6.99 you’ll be able to receive encrypted calls. There’s an additional $24.99 one time in-app purchase for the ZRTP extension to be able to make secure calls. To support future developments of Ostel and other open source projects such as this, I didn’t mind paying the cost to have a backup secure call option. Ostel is free for Android.

Once setup, Ostel functions just like the free iPhone & Android Signal app.  Both use the ZRTP protocol for end to end encrypted communications.


For Android, Ostel has provided a visual tutorial on how to set it up. Here it is in 14 steps:

  1. To get started using Ostel with Android, go to Ostel.co and click on Sign me up and complete the process.
  2. Download the android app CSipSimple.
  3. Open CSipSimple
  4. Press the key icon to add an account.
  5. Add an account.
  6. Scroll down and click the Open Secure Telephony Network (OSTN) account wizard under Expert.
  7. You’ll find empty account info.Fill in your newly created Ostel account information.
  8. You will use the information in the email sent to you.
  9. To confirm it works, you’ll see OSTN turn green . You are registered!
  10. To test it, dial 9196 to do an echo test.
  11. In the echo test, you should be able to hear your own voice. Say something. You should hear the words you just said echoed.
  12. Call someone with Ostel.
  13. A confirmation code will pop up. Read it to them. If you both have the same code, you’re secure.
  14. The status should now say “ZRTP – Verified”, showing you that you’re secure.