2

Signal and Telegram are both mobile applications that "try" to ensure secure chats.

Signal uses end-to-end encryption, Telegram does this as well (in 'secret chats') but it does not use end-to-end encryption in group chats.

How come? Is it difficult to implement?

closed as primarily opinion-based by Xander, Ohnana, LvB, BadSkillz, Matthew Mar 18 '16 at 17:10

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

  • 1
    Not too big a worry as Telegram has already been shown to have garbage encryption. – Fiasco Labs Mar 18 '16 at 18:13
4

As far as guessing anyones motivation for not doing something goes:

Yes, especially group chat is not easy to implement as secure key sharing in groups is quite a challenge when you consider what happens if anyone leaves the group for example.

Threema does (claim to) securely encrypt group chats, as does Tox. As Tox is open source, you may want to have a look there. Given: their mobile apps are in beta right now (at least for iOS).

3

Please specify your question, are you asking wether Telegram does not use end-to-end encryption or does not use multi-party encryption or do you want to know if its difficult to implement?

Encryption is hard and especially group chat encryption is nothing to underestimate. Signal implementes a flavor of OTR, called Multi-party Off-the-Record Messaging (end-to-end encrypted group chat).

Telegram "Secret" Chats are end-to-end encrypted using an own protocol called MTProto, "Normal" Chats and Group-Chats on the other side are not end-to-end encrypted, allowing users to use multiple devices for the same chat and download chatlogs on multiple devices too.

Seemingly, the developers of Telegram value the usability higher than messaging security.

Take a look at the Whisper Systems Blog Post and the MPOTR Whitepaper: https://whispersystems.org/blog/private-groups/ http://www.cypherpunks.ca/~iang/pubs/mpotr.pdf

Also related: Are Telegram secret chats secure assuming MTProto isn't?

  • Telegram allows you to use different clients with the same account at the same time, e.g. Telegram on your mobile and Telegram Desktop. So at any given time, a new "party" (new client from existing user) can join. – Johannes Kuhn Mar 18 '16 at 11:59
  • 1
    You are describing the telegram (not-end-to-end) encrypted chats. A new client is able to join and accessing the vanilla chat and chatlogs. Logically this would not be possible if the chats are end-to-end encrypted. Possibly the developers value this feature higher than messaging security. – hub Mar 18 '16 at 12:03
  • 1
    Exactly. It's always a weighting between usability and security. Telegrams end-to-end encrypted chats ("secret chats") are bound to the devices that were used to start that chat. – Johannes Kuhn Mar 18 '16 at 13:46

Not the answer you're looking for? Browse other questions tagged or ask your own question.