Service use brings significant risks related to information ownership, privacy or security. (Read more)
The service if produced entirely or partly outside EU/ETA area. The customer is responsible for fulfilment of european data privacy and information security requirements. (Read more)
Signal
Signal is an encrypted communications application for Android and iOS. There is a DeskTop plugin for Google Chrome as well
Interoperability with other messaging software
Encryption for messages and phone calls
Free licencing enables interested parties to examine the code
Possibility for Group Conversations
Enclosing Multimedia is possible
Signal´s official Android App needs Google Play because App depends on Google´s GMC developement
Terms of Service & Privacy Policy
Signal does not have any Terms Of Use policy or EULA, only Privacy Policy: https://whispersystems.org/signal/privacy/
Login
Login happens with one´s mobile number. Service will be activated via SMS. Service is used via mobile app.
Signal demands that primary device is Android or Ios device (smart phone) with Internet connection.
Support
http://support.whispersystems.org
(No eula or agreement = no guarantee).
Service Provider
Open Whisper Systems (https://whispersystems.org)
Signal is developed by a software group called Open Whisper Systems. The group is funded by a combination of donations and grants, and all of its products are published as free and open-source software.
Similar services
WhatsApp, Telegram, Chatsecure, Bleep
Common notes:
In this service Mobile Apps will send so called end to end (forward secrecy, end-to-end), encrypted messages, service quite is alike with WhatsApp, which is propably more known by public. Service is well protected for Man-In-the-Middle attacks and eavesdropping.
Revenue logic:
The group is funded by a combination of donations and grantsand crowd funding, and all of its products are published as free and open-source software. Different Foundations also support OpenWhisperSystem. Technical description of Signal can be found: http://support.whispersystems.org
Security and Privacy:
All program code can be revievew at GitHub. Signal may be the only one this kind of software, which code can be reviewed entirely (including Proxy Servers. ?)
Service uses centralized Proxy Server which transmits messages and checks from users address book if communication contacts are using Signal. Location and compositoin of Proxies are not available, propably those are in U.S but messages stay encypted in transmission. Some data for example time stamps, public encryption key, PUSH-ID and IP address may be captured by authorities.
Possible communication companies are compaired using users address books from mobile phones and users address books from Signal´s customer database. Comparision algorithm is said to be one way procedure in a way users adress book can not be exposed from server.