There are a few encrypted messaging apps out there like Telegram, Viber, LINE, WhatsApp but Signal is often the most recommended one by world’s renowned personalities like Edward Snowden, Laura Poitras, Bruce Schneier, Matt Green etc.
Signal encrypted messenger uses Signal protocol. It is designed to not store or collect any sensitive information. Signal calls and messages are secure and cannot be accessed by app developers or other 3rd parties, as they are always secure, private and end-to-end encrypted.
The protocol was developed by Open Whisper Systems and it has been implemented by other messengers such as Facebook Messenger, WhatsApp and Skype. Signal protocol is a combination of prekeys, Double Ratchet Algorithm and a Triple Elliptic-curve-Diffie-Hellman (3XDH) handshake. Protocol uses HMAC-SHA256, AES-256 and Curve25519 as primitives.
The protocol provides participant consistency, destination validation, confidentiality, integrity, authentication, causality preservation, backward secrecy (aka future secrecy), forward secrecy, message repudiation, message unlinkability, participation repudiation, and asynchronicity. It doesn’t provide anonymity preservation as well as needs servers for the relaying of messages and storing of public key material.
All Signal communications are protected by TLS. Recently, a ‘Sealed Sender’ option has been introduced which encode the users’ information using the sender as well as recipient identity keys and contains it inside the message. With ‘Sealed Sender’ option, Signal servers cannot see who is sending message to whom.
Signal protocol does not allow servers to keep logs about who called whom and when. CEO, creator of Signal and co-founder of the Signal Foundation, Moxie Marlinspike said “The closest piece of information to metadata that the Signal server stores is the last time each user connected to the server, and the precision of this information is reduced to the day, rather than the hour, minute, and second“.
Registration lock is improved with secure value recovery. Registration lock allows users to set a PIN for account registration. With the introduction of Secure Value Recovery, the security of PIN is enhanced. This function works the same way as any password.
In the latest Signal beta, emoji reactions have been introduced. With Signal emoji reactions, now users can react. Along with one-to-one chats, emoji reactions will also improve the group messaging experience.
Signal announced support for stickers nearly two months ago. Since then, more than 5000 sticker packs have been uploaded including latest ones i.e. Faces and Hands by Swoon. All sticker packs are encrypted.
Signal users can also compare key fingerprints in order to verify correspondent’s identity. If a correspondent’s key is changed, user will be notified.
Centralized servers have been set up for Signal messenger. Along with transmitting Signal’s messages, the servers also offer automatic exchange of users’ public keys. Signal video and voice calls are peer-to-peer. If a caller is not in the contact list of the receiver, the call will be transmitted via a server to prevent showing users’ IP addresses.
The servers store registered users’ push tokens, public key material and phone numbers which are mandatory for transmitting messages and setting up calls.
The entire main codes of the Signal app for iOS, Android and desktop are available on GitHub under a free software license. Open source nature of Signal app allows parties to audit the code and help the app developers in verifying that everything is working fine as expected. It also let users to build their own copies of the application so that they can compare them with the codes distributed by Signal messenger.
Official Signal app can be downloaded from the Apple’s app store, Google Play Store and the official website. Android version of the app is checked by the Android Operating System to confirm that updates are signed with the same key whereas same applies with the app’s iOS version. There is also a separate APK package binary of Signal App that can be downloaded from Signal Messenger’s website.
End-to-end encryption, advanced security features and free to use make Signal app the most popular and recommended encrypted messenger.
So, get Signal now!