Tech Untangled: Signal Private Messenger provides encrypted texting and more

technology-bourThe use of encrypted messaging apps has been a recurring storyline in the news. One recent story about a terrorist attack in London discussed how the attacker used the WhatsApp messenger to communicate with someone just minutes before he drove his vehicle into people on a bridge. Authorities were unable to gain information from that conversation because of the end-to-end encryption protocol that was used by the messaging app. The WhatsApp service, which is owned by Facebook, simply does not have the ability to read encrypted messages sent and received by users of the app. There is no “back door.” The balance between privacy and security is a political discussion for others to address. From a purely technical viewpoint, I decided to investigate a similar encrypted messaging app called Signal Private Messenger.

I was looking for an easy-to-use encrypted messaging app specifically for texting, and Signal popped up on several searches. What caught my attention was a quote on its website (, supposedly by infamous whistleblower Edward Snowden, that said, “Use anything by Open Whisper Systems.” This app, like other similar offerings, was free, so what did I have to lose?

Installation was straightforward. I downloaded the Android app from the Google Play Store. For comparison, I also downloaded a version for my iPhone from the Apple App Store. When you sign up, your phone communicates with the Signal servers, and you are sent a verification code that gets texted to your existing messaging app. One twinge of discomfort came with the next step. Signal asked for access to my entire contact list and imported it into their messaging app. They specifically said, “We do not store your contacts on our server,” and also said that they do not have access to any of your communications. Who knows if that is really a fact. The next step provided an invitation message that I could send individually to my contacts and invite them to download and use the app, too.

You can use the Signal messaging app in place of your present app to text with anyone, but you are only able to negotiate secure and encrypted communication if both parties are using the Signal app. To make that clear, the Send icon for entering standard messages shows an open padlock. When you are messaging with another Signal user, the Send icon shows a locked padlock. The first time you communicate with a new Signal user, the two phones link through the Signal server and create a secure channel with a unique safety code number that stays in place for all future messages.

Messages that are negotiated in the Signal app will not show up in your regular text messaging app, and vice versa. A record of your conversations within the Signal app will remain in your phone until you choose to delete them. That got me to wondering why the authorities in criminal matters couldn’t simply look at the conversational threads on a bad guy’s phone. I think I know why this doesn’t always work. There is a feature called “Disappearing Messages.”

Disappearing Messages, as the name implies, will allow you to send a message that will erase just a few seconds after a recipient has viewed it. You can set that time for five seconds or longer. This feature is similar to the disappearing picture function of the popular Snapchat app. Your recipient receives a notice that the incoming message is soon to evaporate, so they better read fast!

Like other SMS messaging apps, you can also attach photos, video and audio. Signal allows all this to be encrypted as well. What I next learned, to my surprise, was that Signal also offers the ability to make encrypted voice and video calls. The system does this through some type of IP data protocol that does not use a normal cellphone connection and does not log any cellphone minutes or retain any cell call data with your service provider. For good or bad, this allows a person to make untraceable voice calls, as well as secure Facetime-style video calls. You are, of course, still using up your monthly data allowance unless you are connected to Wi-Fi.

Some anonymity could normally be revealed by tracking down the IP address where a call originates, but Signal Private Messenger has thought of that, too, and provides an option to relay calls through the Signal server to avoid revealing your IP address. They advise that the call quality could be degraded somewhat. I found that, with or without this feature, the call quality was not that great. I noticed a fair amount of garbled and distorted audio when making test phone calls.

I had some other minor complaints. The transmission time for a text to be received was noticeably longer than with standard texting, but not excessive. The feel and the utility of the Signal app were better executed with the Android version than the iPhone, but both are functional. Unfortunately, iPads and tablets are not yet supported, only smartphones at this time.

If privacy is a growing concern to you, I think the Signal Private Messenger app is worth a look. Whether you use it or not, it is important for you to be informed that encrypted communication tools like this are easily available and are being utilized by others.•


Stephen Bour ([email protected]) is an engineer and legal technology consultant in Indianapolis. His company, the Alliance for Litigation Support Inc., includes Bour Technical Services and Alliance Court Reporting. Areas of service include legal videography, tape analysis, document scanning to CD and courtroom presentation support. The opinions expressed in this column are those of the author.

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