Telegram (software)

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Telegram
Developer(s)Telegram Messenger LLP
Initial releaseAugust 2013; 10 years ago (2013-08)
Stable release
Android10.12.0[1] Edit this on Wikidata / 25 April 2024; 29 days ago (25 April 2024)
iOS, iPadOS10.12[2] Edit this on Wikidata / 25 April 2024; 29 days ago (25 April 2024)
Windows, macOS, Linux
(Telegram Desktop)		5.0.1[3] Edit this on Wikidata / 4 May 2024; 20 days ago (4 May 2024)
macOS10.12.2[4] Edit this on Wikidata / 28 April 2024; 26 days ago (28 April 2024)
Repository
Operating systemAndroid, iOS, Windows Phone, Ubuntu Touch, Firefox OS, MS Windows, Linux, OS X
Available inEnglish, Arabic, Spanish, German, Italian, Korean, Dutch, Portuguese
TypeInstant messaging
License
Websitetelegram.org

Telegram is a cloud-based instant messaging service. Telegram clients exist for both mobile (Android, iOS, Windows Phone, Ubuntu Touch) and desktop systems (Windows, OS X, Linux).[5][7] Users can send messages and exchange photos, videos, stickers and files of any type up to 1.5 GB in size. Telegram also provides optional end-to-end encrypted messaging with self-destruct timers.

Telegram is supported by the Russian-born entrepreneur Pavel Durov,[8] who is now living in Saint Kitts and Nevis,[9] in self-imposed exile.[10] He founded the Russian social network VK and was its CEO until April 2014. Its client-side code is open-source software in parts, whereas its server-side code is closed-sourced and proprietary. The service also provides APIs to independent developers.

History

Development

Telegram was launched in 2013 by brothers Nikolai and Pavel Durov, who previously founded the Russian social network VK, but had to leave the company after it was taken over by the Russian Government.[10][11] Nikolai Durov created the MTProto protocol that is the basis for the messenger, while Pavel provided financial support and infrastructure through his Digital Fortress fund.[12]

Telegram is registered as both an English LLP[13] and an American LLC.[14] It does not disclose where it rents offices or which legal entities it uses to rent them, citing the need to "shelter the team from unnecessary influence" and protect users from governmental data requests.[15] The service says that it is headquartered in Berlin, Germany.[16] Durov left Russia and is said to be moving from country to country with a small group of computer programmers.[10]

In September 2015, Samsung released a new messaging application based on Telegram Messenger.[17]

Usage numbers

In October 2013, Telegram had 100,000 daily active users.[11] On 24 March 2014, Telegram announced that it had reached 35 million monthly users and 15 million daily active users.[18] In October 2014, South Korean governmental surveillance plans drove many of its citizens to switch to Telegram.[16] In December 2014, Telegram announced they had 50 million active users, generating 1 billion daily messages and that they had 1 million new users signing up on their service every week;[19] traffic doubled in five months with 2 billion daily messages.[20] In September 2015, an announcement stated that the app had 60 million active users and delivered 12 billion daily messages.[21] In February 2016, Telegram announced that they had 100 million monthly active users, with 350.000 new users signing up every day, delivering 15 billion messages daily.[22]

Features

Account

Similar to services like WhatsApp, Telegram accounts are tied to telephone numbers and verified by SMS or phone call.[23] Users can add multiple devices to their account and receive messages on each one. Connected devices can be removed individually or all at once. The associated number can be changed at any time and when doing so, the user's contacts will receive the new number automatically.[23][24][25] In addition, a user can set up an alias that allows them to send and receive messages without exposing their phone number.[26] These aliases or usernames are also linked with an official https://telegram.me/<alias> URL (where <alias> is the chosen username). Usernames can be changed at any time. Accounts can be deleted at any time and they are deleted automatically after six months of inactivity by default, which can optionally be changed to 1 to 12 months. Users can replace exact "last seen" timestamps with fudged messages such as "last seen within a week".[27]

Cloud-based messages

Telegram's default messages are cloud-based and can be accessed on any of the user's connected devices.[28] Users can share photos, videos, audio messages and other files (up to 1.5 gigabyte in size).[5][29] Users can send messages to other users individually or to groups of up to 1000 members.[30] The transmission of messages to Telegram Messenger LLP's servers is encrypted with the service's MTProto protocol.[28] According to Telegram's privacy policy, "all data is stored heavily encrypted and the encryption keys in each case are stored in several other DCs in different jurisdictions. This way local engineers or physical intruders cannot get access to user data".[31]

Bots

In June 2015, Telegram launched a platform for third-party developers to create bots.[32] Bots are Telegram accounts operated by programs. They can respond to messages or mentions, can be invited into groups and can be integrated into other programs. Dutch website Tweakers reported that an invited bot can potentially read all group messages when the bot controller changes the access settings silently at a later point in time. Telegram pointed out that it considered implementing a feature that would announce such a status change within the relevant group.[33]

Channels

Channels can be created for broadcasting messages to an unlimited number of subscribers.[34][35] Channels can be publicly available with an alias and a permanent URL so anyone can join. Users who join a channel can see the entire message history. Each message has its own view counter, showing how many users have seen this message. Users can join and leave channels at any time. Furthermore users can mute a channel, meaning that the user will still receive messages, but won't be notified.

Stickers

Stickers are cloud-based, high-definition images intended to provide more expressive emoji. When typing in an emoji, the user is offered to send the respective sticker instead. Stickers come in collections called "sets", and multiple stickers can be offered for one emoji. Telegram comes with one default sticker set,[36] but users can install additional sticker sets provided by third-party contributors. Sticker sets installed from one client become automatically available to all other clients.

Secret chats

A "secret chat" confirmation notice - screenshot from Android Marshmallow.

Messages can also be sent with client-to-client encryption in so-called secret chats that are not cloud-based. Secret chat messages are encrypted with the service's MTProto protocol.[37] Contrary to Telegram's cloud-based messages, messages sent within a secret chat can only be accessed on the device upon which the secret chat was initiated or accepted; they can't be accessed on other devices.[11][28][38] Secret chats have to be initiated and accepted by an invite, upon which the encryption keys for the session are exchanged. Messages sent within secret chats can, in principle, be deleted at any time and can optionally self-destruct.[39] Some Telegram clients also allow users to encrypt the local message database using a passphrase.[40]

According to Telegram, secret chats support perfect forward secrecy since December 2014. Encryption keys are periodically changed after a key has been used more than 100 times or has been in use for more than a week. Old encryption keys are destroyed.[24][25][41]

Architecture

Encryption scheme

A simplified illustration of the MTProto encryption scheme.

Telegram uses a symmetric encryption scheme called MTProto. The protocol was developed by Nikolai Durov and other developers at Telegram and is based on 256-bit symmetric AES encryption, RSA 2048 encryption and Diffie–Hellman key exchange.[37]

Since 2013,[42] cryptography experts have expressed both doubts and criticisms on the MTProto encryption scheme, saying that deploying home-brewed and unproven cryptography may render the encryption vulnerable to bugs that potentially undermine its security, due to a lack of scrutiny.[43][44] It has also been suggested that Telegram did not employ developers with sufficient expertise or credibility in this field.[45]

In December 2015, two researchers from Aarhus University published a report in which they demonstrated that MTProto does not achieve indistinguishability under chosen-ciphertext attack (IND-CCA) or authenticated encryption.[43] The former means that it is possible to turn any ciphertext into a different ciphertext that decrypts to the same message. The researchers stressed that the attack was of a theoretical nature and they "did not see any way of turning the attack into a full plaintext-recovery attack".[43]

Servers

Telegram Messenger LLP has servers in a number of countries throughout the world to improve the response time of their service.[46] Telegram's server-side software is closed-source and proprietary. Pavel Durov has said that it would require a major architectural redesign of the server-side software to connect independent servers to the Telegram cloud.[47]

List of client applications

Telegram has various clients. This list includes versions developed on official platforms backed by Telegram Messenger LLP and unofficial clients that are developed by the community. The source code of all official Telegram clients (and some of the unofficial clients) is open source and released under the GNU General Public Licence version 2 or 3.

Name Platform(s) Official Source code license Support for secret chats Notes
Telegram OS X Yes GPLv2[48] Yes
Telegram Desktop Microsoft Windows (portable application), OS X, and GNU/Linux Yes GPLv3 with OpenSSL exception[49] No
Cutegram Windows, OS X, and Linux No GPLv3[50] Yes Based on Qt.[51]
Telegram CLI Linux No[52] GPLv2[53] Yes Command-line interface for Telegram.
Telegram Messenger iOS 6 or later Yes GPLv2 or later[52][54] Yes Launched in August 2013 for iPhone and iPod Touch and relaunched in July 2014 with support for iPad.[55]
Telegram Android 2.3 or later Yes GPLv2 or later[52][56] Yes Supports tablets[57] and Android Wear smart watches.[58]
Telegram Messenger Windows Phone Yes GPLv2 or later[52] Yes
Telegram Firefox OS Yes GPLv3[59] No Based on Webogram.
Telegram Google Chrome and Chrome OS Yes GPLv3[59] No
Telegram Ubuntu Touch No GPLv2[60] Yes
Sailorgram Sailfish OS No GPLv3[61] Yes Based on Cutegram.

Users can also access Telegram's cloud-based messages via an official web browser interface called Telegram Web (aka Webogram). Users can share images, files and emoticons with previously-added contacts; this works in most modern browsers, such as Firefox, Safari, and Google Chrome.[52][59]

Reception

Security

On 26 February 2014, the German consumer organisation Stiftung Warentest had evaluated several data-protection aspects of Telegram, along with other popular instant-messaging clients. Among the aspects considered were: the security of the data transmission, the service's terms of use, the accessibility of the source code and the distribution of the app. Telegram was rated 'critical' (kritisch) overall. The organisation was favourable to Telegram's secure chats and partially open source code, but criticised the mandatory transfer of contact data to Telegram's server and the lack of an imprint or address on the service's website. It noted that while the message data is encrypted on the device, it could not analyse the transmission due to a lack of source code.[62]

The Electronic Frontier Foundation (EFF) has listed Telegram on its "Secure Messaging Scorecard". As of 7 December 2015, Telegram's default chat function has a score of 4 out of 7 points on the scorecard. It has received points for having communications encrypted in transit, having its code open to independent review, having the security design properly documented, and having completed an independent security audit. Telegram's default chat function is missing points because the communications are not encrypted with keys the provider doesn't have access to, users can't verify contacts' identities, and past messages are not secure if the encryption keys are stolen. Telegram's optional secret chat function, which provides end-to-end encryption, has a score of 7 out of 7 points on the scorecard.[63] An earlier version of the EFF's scorecard was criticized for being inaccurate, misleading and vague, but not specifically with regard to its evaluation of Telegram.[64]

Cryptography contests

Telegram has organised two cryptography contests to challenge third parties to break the service's cryptography and disclose the information contained within a secret chat between two fake users. A reward of respectively US$200,000 and US$300,000 was offered. Both of these contests expired with no winners.[65][66] Security researcher Moxie Marlinspike and commenters on Hacker News criticised the first contest for being rigged or framed in Telegram's favour and said that Telegram's statements on the value of these contests as proof of the cryptography's quality are misleading.[67][68][69]

Censorship

Telegram was open and working in Iran without any VPN or other circumvention methods in May 2015.[70] In August 2015, the Iranian Ministry of ICT asserted that Telegram had agreed to restrict some of its bots and sticker packs in Iran at the request of the Iranian government.[71] According to an article published on Global Voices, these features were being used by Iranians to "share porn and satirical comments about the Iranian government". The article also noted that "some users are concerned that Telegram's willingness to comply with Iranian government requests might mean future complicity with other Iranian government censorship, or even allow government access to Telegram's data on Iranian users".[71] However Telegram stated that all Telegram chats are private territory and that they do not process any requests related to them. Only requests regarding public content (bots and sticker packs) will be processed.[72]

Use by terrorists

In September 2015, in response to a question about the use of Telegram by extremists like ISIL, Pavel Durov stated: "I think that privacy, ultimately, and our right for privacy is more important than our fear of bad things happening, like terrorism."[73] ISIL has recommended Telegram to its supporters and members[74][75] and in October 2015 they were able to double the number of followers of their official channel to 9,000.[76] In November 2015, Telegram announced that it had blocked 78 public channels operated by ISIL, which were used for spreading propaganda and mass communication.[77][78] Telegram stated that it would block public channels and bots that are related to terrorism, but it would not honour "politically-motivated censorship" based on "local restrictions on freedom of speech" and that it allowed "[peaceful expression of] alternative opinions".[79] Telegram's usage for ISIL's propaganda has reignited the encryption debate and encrypted messaging applications have faced new scrutiny.[80][81]

See also

References

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  70. ^ "تلگرام فیلتر نشده است" (in Persian). Tehran: Tasnim News Agency. 11 May 2015. Retrieved 29 October 2015. Though it is claimed by many that the Telegram is banned, but it is operating normally in Iran.
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  81. ^ Foges, Clare. "Why is Silicon Valley helping the tech-savvy jihadists?". The Telegraph. Retrieved 9 December 2015.

External links

Wikimedia Commons has media related to Telegram Messenger.
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