Signal, a private encrypted messenger service, is known for its privacy and security features. What makes it a favourite of privacy advocates and tech giants?
The new policies resulted in an exodus of users to safer alternatives like Signal. Adding fuel to the fire, billionaire entrepreneur Elon Musk tweeting “Use Signal” to his 42 million followers sent the app’s downloads soaring. The combined effects of these two events were so potent that Signal’s servers were briefly overloaded, delaying the receipt verification codes for users to sign up.
The app also made it to the top of the free app charts on India’s App Store.
“We can barely register our excitement,” the messenger service’s Twitter account tweeted last week.
What is Signal?
Widely used by journalists, lawyers, politicians, security experts, and researchers, Signal is a messaging application that is known for its privacy and security features. It has also been endorsed by privacy advocate Edward Snowden and Twitter CEO Jack Dorsey.
One of the important features that differentiates Signal from WhatsApp is that it’s an open-source app. This means that it can be inspected by security experts to verify security and flag any issues with the code.
The app has been developed by the Signal Foundation and Signal Messenger LLC. An independent nonprofit, Signal has no adverts or ad trackers, the company isn’t tied to any other major tech companies, and has previously said it and won’t be acquired by one, either.
The Signal Foundation was created by WhatsApp Co-founder Brian Acton and Moxie Marlinspike, Signal Messenger’s current CEO. Acton, who left WhatsApp in 2017, invested around $50 million in Signal.
“As more and more of our lives happen online, data protection and privacy are critical,” Acton had then said. “This isn’t just important for select people in select countries. It’s important for people from all walks of life in every part of the world. Everyone deserves to be protected. We created the Signal Foundation in response to this global need.”
Signal can be downloaded from the Android Play Store and the iPhone App Store and is available for Android, iPhone, iPad, Windows, Linux, and Mac.
Signal’s privacy features
From end-to-end encryption to relay calls, Signal offers a number of features to keep your texts, calls, and media secure.
As with WhatsApp, Signal uses end-to-end encryption to keep all forms of conversation secure.
“We can’t read your messages or listen to your calls, and no one else can either. Privacy isn’t an optional mode – it’s just the way that Signal works. Every message, every call, every time,” the company says on its website.
Signal encrypts everything–texts, voice and video calls, photos, attachments, and even stickers and GIFs. Additionally, it has a ‘Sealed Sender’ feature, through which the sender and recipient’s details are hidden from Signal.
However, the encryption works only for Signal-to-Signal communications. This means that if you’re communicating with someone who hasn’t installed Signal, communications are still unsecured.
Securely back up chats
Unlike WhatsApp, Signal doesn’t back up your data to Google Drive or iCloud. When your data is stored on another server, it is vulnerable to cyberattacks. On Signal, all your texts, images, files, and other data are securely stored in an encrypted database on your device.
This means that if you lose your old phone and set up Signal on a new device, your previously-stored data will be gone. However, you can transfer your data if you still have your old device or haven’t deleted the data from it.
While the disappearing messages feature is relatively new for WhatsApp, it’s existed on Signal for a long time. This feature, which can be activated or deactivated by anyone in the chat, lets you set a timer between 10 seconds and one week, and any messages older than the set time will disappear.
Incognito keyboard to keep other apps from seeing what you type
Third-party keyboard apps on your Android device can keep a record of what you type and swipe, thereby compromising the privacy of your messages. To prevent this, Signal has an Incognito Keyboard option, which prevents your keyboard from learning what you type.
Relay calls to hide your IP address
The relay calls feature on Signal allows you to call any other user through a relay service. This means that when you enable this feature, all the calls you place will be relayed through a Signal server, thereby hiding your IP address from your contact.
While this may not be a necessity for most people, it essentially allows for confidential conversations with other Signal users.
Safety number to verify security of messages and calls
Each one-to-one chat on Signal has a unique safety number that allows you to verify the security of your messages and calls with specific contacts. For sensitive communications, you can verify the safety numbers of your contact.
If both you and your contact’s safety numbers match, it means that you’re communicating with the right person. Signal will alert you whenever a safety number has changed. If this happens frequently, its may be an indication that something is wrong.
Screen security to prevent previews
In addition to the screen lock feature designed to lock your Signal screen, the app also has a feature called screen security, which prevents Signal previews from appearing when you’re switching apps or pulling down the notification bar.
When enabled, the feature will hide your Signal messages with a blue privacy screen. Additionally, on Android, this feature will also prevent screenshots of Signal on your device.
Signal PIN to secure profile information
Another feature Signal has is a registration lock PIN, with which users can protect their private profile information. Additionally, this number can also be used to retrieve your profile, settings, contacts, or information such as who you have blocked, if you lose your device or switch to a new one.
However, as Signal doesn’t have access to your keys or data, if your forget your PIN, you can’t recover your account. To help you remember your PIN, Signal will also send you periodic reminders.
View-once media is another handy Signal feature that doesn’t exist on WhatsApp. By using this feature, the individual photos and videos you send will be automatically removed from a conversation after they have been viewed.
Send blurred photos and videos
Signal introduced a blur feature last year to help protect the privacy of people in the images you share. If enabled, it automatically blurs any faces it detects when you’re using the in-app camera. You can also manually blur additional faces or areas in the photo using the blur brush option. Furthermore, all the processing happens on your device, thereby maintaining your privacy.
Signal also has features to keep read receipts off, delete messages, direct reply to a specific message, link multiple devices, and add a screen lock. It also has a ‘Note to Self’ feature which enables you to send messages to yourself. This feature can be used to make a note for yourself. These features are also available on WhatsApp. However, unlike WhatsApp, you can also send disappearing messages to yourself.
With Signal, you can also react with emojis to messages, turn off typing indicators, remove Signal calls from call lists, and more.
What data does Signal collect?
“Signal does not sell, rent or monetize your personal data or content in any way – ever,” the company says.
Unlike WhatsApp, Signal only collects your account information, i.e. the phone number you used to register on Signal. Information such as your profile name and profile picture are also end-to-end encrypted.
Signal does not collect your contacts. However, in order to check if any of your contacts are also using Signal, the app periodically sends truncated, hashed phone numbers back to Signal’s servers. However names are not transmitted and the information is not stored on the servers. Once the server responds with the contact that use Signal, the information is immediately discarded.
While Signal doesn’t store your messages on their servers, it “queues end-to-end encrypted messages on its servers for delivery to devices that are temporarily offline.”
Signal adds that it may share some information with third parties to provide some services, such as those used to send a verification code to your phone when you register with Signal. However, these providers “are bound by their Privacy Policies to safeguard that information.”
To sum it up, Signal collects the least metadata compared to other private messaging apps like WhatsApp. With a slew of privacy features, the app is ideal for anyone who wants to keep their data private and secure.
Header image courtesy of Signal