Unfortunately, WhatsApp is not a secure messaging application , considering that it can be "hacked" in multiple ways and that even the authorities can spy on your WhatsApp . In the case of SMS and conventional calls , the police can also obtain all this information from the mobile operator if required (1). Applications such as Apple's iMessage store a large amount of message and call metadata on their servers, such as contacts and location, which authorities can easily obtain from Apple with a court order (2)..
Several of the downsides to the above apps or services are things Signal doesn't suffer from , probably the most secure calling and messaging app out there today. Unlike WhatsApp, iMessage and other applications, Signal saves minimal information on its servers, such as the last connection or creation date of the users account (2), so even though the authorities will request more information about an account , the company could not offer it.
Signal privacy options for Android, where you can prevent your information from being saved on servers, such as sender data or IP address..
As the screens above show, it is evident all the privacy and security settings that Signal offers compared to WhatsApp and other messaging apps. Although it is very similar in the initial configuration, requiring you to enter your phone number to create an account, in its settings there are several interesting options.
In addition to the typical options to block your account with a PIN or password access to the application , you have advanced options such as the confidential sender , which avoids saving your information as a sender on Signal's servers, or the option to hide your IP during a call ..
There are also other interesting options to block the screenshots in the application and prevent them from seeing you when you are writing something , which I personally would like to have in WhatsApp.
Similarity to WhatsApp and other messaging apps
Leaving aside the security and privacy that Signal offers, it is not so different from WhatsApp, Telegram, Messenger and other instant messaging apps in the rest of the sections. For example, here are all the emojis that exist in WhatsApp , supports stickers , GIFs , voice notes , automatic disappearance of messages , reactions to messages and backup of chats in an encrypted file in the device memory, use on multiple devices, etc. .
Signal can also be used as an SMS application , which can be sent by pressing and holding the "+" button in the lower left part of the chat, option "SMS not secure".
However, sending SMS via Signal is just as insecure as if you sent it via the default SMS app on your cell phone . In other words, the metadata of the SMS will be stored on your operator's servers. You are sending the SMS over the mobile operator's network, the way you always have. For your messages to be really safe, you must use the blue option "Signal", which sends messages over the Internet, either WiFi or mobile data.
If you want to send secure SMS, you can take a look at TextSecure , another application from Open Whisper Systems, the creator of Signal, which offered the option of camouflaging these SMS that were sent through a mobile operator's network, encrypting and decrypting from Locally each and every one of these messages and making them private, so that the only person who can read them is the one to whom we have sent them. Unfortunately, this application disappeared from the Play Store and although its APK can be found on the Internet, it has not been updated since 2014, so it may not work on current devices.
References : RT (1), The Hacker News (2)
Download Signal: Official website
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