Telegram (messaging service)
Telegram running on Android Lollipop
|Developer(s)||Telegram Messenger LLP|
|Initial release||August 2013|
|Platform||Web platform, Windows NT, macOS, Linux, Android, iOS, Windows Phone|
|Available in||8 languages|
|License||GNU GPLv2 or GPLv3|
Telegram is a free, non-profit cloud-based instant messaging service. Telegram client apps exist for Android, iOS, Windows Phone, Windows NT, macOS and Linux. Users can send messages and exchange photos, videos, stickers, audio, and files of any type. Telegram also provides optional end-to-end-encrypted messaging.
Telegram is supported by Russian entrepreneur Pavel Durov. Its client-side code is open-source software but contains binary blobs, and the source code for recent versions is not always immediately published, whereas its server-side code is closed-source and proprietary. The service also provides APIs to independent developers. In February 2016, Telegram stated that it had 100 million monthly active users, sending 15 billion messages per day.
The security of Telegram has faced notable scrutiny; critics have claimed that Telegram's security model is undermined by its use of a custom-designed encryption protocol that has not been proven reliable and secure, and by not enabling secure conversations by default. Telegram has also faced criticism for its wide-scale use by the ISIL terrorist organization.
- 1 History
- 2 Features
- 3 Architecture
- 4 Reception
- 5 See also
- 6 References
- 7 Further reading
- 8 External links
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 Mail.ru Group. 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 with business partner Axel Neff, a third founder of Telegram.
Telegram is registered as both an English LLP and an American LLC. 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. The service says that it is headquartered in Berlin, Germany. Durov left Russia and is said to be moving from country to country with a small group of computer programmers.
In October 2013, Telegram had 100,000 daily active users. On 24 March 2014, Telegram announced that it had reached 35 million monthly users and 15 million daily active users. In October 2014, South Korean governmental surveillance plans drove many of its citizens to switch to Telegram. 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; traffic doubled in five months with 2 billion daily messages. In September 2015, an announcement stated that the app had 60 million active users and delivered 12 billion daily messages. 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.
Telegram accounts are tied to telephone numbers and are verified by SMS or phone call. 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. In addition, a user can set up an alias that allows them to send and receive messages without exposing their phone number. Telegram 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 month and 12 months. Users can replace exact "last seen" timestamps with broader messages such as "last seen recently".
The default method of authentication that Telegram uses for logins is SMS-based single-factor authentication. All that is needed in order to log into an account and gain access to that user's cloud-based messages is a one-time passcode that is sent via SMS to the user's phone number. These login SMS messages are known to have been intercepted in Iran, Russia and Germany, possibly in coordination with phone companies. Pavel Durov has said that Telegram users in "troubled countries" should enable two-factor authentication by creating passwords, which Telegram allows, but does not require.
In June 2015, Telegram launched a platform for third-party developers to create bots. 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. Also there are inline bots, which can be used from any chat screen. In order to activate an inline bot, user needs to type in the message field a bot's username and query. The bot then will offer its content. User can choose from that content and send it within a chat.
Channels can be created for broadcasting messages to an unlimited number of subscribers. 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 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, 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. Sticker images use WebP file format, which is better optimized to be transmitted over internet.
Drafts are unfinished messages synced across user devices. One can start typing a message on one device and continue on another. The draft will persist in editing area on any device until it is sent or removed.
Messages can also be sent with client-to-client encryption in so-called secret chats. These messages are encrypted with the service's MTProto protocol. Unlike Telegram's cloud-based messages, messages sent within a secret chat can be accessed only on the device upon which the secret chat was initiated and the device upon which the secret chat was accepted; they cannot be accessed on other devices. Messages sent within secret chats can, in principle, be deleted at any time and can optionally self-destruct.
Secret chats have to be initiated and accepted by an invitation, upon which the encryption keys for the session are exchanged. Users in a secret chat can verify that no man-in-the-middle attack has occurred by comparing pictures that visualize their public key fingerprints.
According to Telegram, secret chats have supported 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.
Windows and Linux users are still not able to use secret chats using the official Telegram Desktop app while the official macOS-only client supports them. 
Secret chats are not available for groups or channels.
In the end of March 2017, Telegram introduced its own voice calls. The calls are built upon the end-to-end encryption of Secret Chats. Connection is established as peer-to-peer whenever possible, otherwise the closest server to the client is used. According to Telegram, there is a neural network working to learn various technical parameters about call to provide better quality of the service for future uses. After a brief initial trial in Western Europe, voice calls are now available for use in most countries.
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.
Telegram Messenger LLP has servers in a number of countries throughout the world to improve the response time of their service. 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.
Telegram has various client apps. 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 Desktop||Windows NT (traditional, portable and UWP app), macOS, and Linux||Yes||GPLv3 with OpenSSL exception||No|
|Cutegram||Windows, macOS, and Linux||No||GPLv3||Yes||Based on Qt.|
|Telegram CLI||Linux, FreeBSD and macOS||No||GPLv2||Yes||Command-line interface for Telegram.|
|MadelineProto||Linux, FreeBSD, Windows and macOS||No||AGPLv3||Yes||Telegram library with support for secret chats and telegram voice calls|
|Telegram Messenger||iOS 6 or later||Yes||GPLv2 or later||Yes||Launched in August 2013 for iPhone and iPod Touch and relaunched in July 2014 with support for iPad.|
|Telegram||Android 2.3 or later||Yes||GPLv2 or later||Yes||Supports tablets and Android Wear smart watches.|
|Telegram Messenger||Windows Phone||Yes||GPLv2 or later||Yes|
|Telegram||Firefox OS||Yes||GPLv3||No||Based on Webogram.|
|Telegram||Google Chrome and Chrome OS||Yes||GPLv3||No|
|Telegram[third-party source needed]||Ubuntu Touch||No||GPLv2||Yes|
|Sailorgram[third-party source needed]||Sailfish OS||No||GPLv3||Yes||Based on Cutegram.|
|Telegram-Purple||Windows, macOS, and Linux||No||GPLv2||Yes||Plugin for Pidgin, Adium, Finch and other Libpurple-based messengers|
|Unigram||Universal Windows Platform||No||GPLv3||No|
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.
Telegram has public APIs with which developers can access the same functionality as Telegram's official apps to build their own messaging applications. In February 2015, creators of the unofficial Whatsapp+ client released the Telegram Plus app, later renamed to Plus Messenger, after their original project got a cease-and-desist order from WhatsApp. In September 2015, Samsung released a messaging application based on these APIs.
Telegram also offers an API that allows developers to create bots, which are accounts controlled by programs. In February 2016, Forbes launched an AI-powered news bot that pushes popular stories to subscribers and replies to search queries with relevant articles. TechCrunch launched a similar bot in March 2016.
||The neutrality of this section is disputed. (April 2017) (Learn how and when to remove this template message)|
Cryptography experts have expressed both doubts and criticisms on Telegram's 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. It has also been suggested that Telegram did not employ developers with sufficient expertise or credibility in this field.
Critics have also disputed claims by Telegram that it is "more secure than mass market messengers like WhatsApp and Line", because WhatsApp applies end-to-end encryption to all of its traffic by default and uses a protocol that has been "reviewed and endorsed by leading security experts", while Telegram does neither and insecurely stores all messages, media and contacts in their cloud. Since July 2016, Line has also applied end-to-end encryption to all of its messages by default.
The Electronic Frontier Foundation (EFF) listed Telegram on its "Secure Messaging Scorecard" in February 2015. Telegram's default chat function received a score of 4 out of 7 points on the scorecard. It received points for having communications encrypted in transit, having its code open to independent review, having the security design properly documented, and having completed a recent independent security audit. Telegram's default chat function missed points because the communications were not encrypted with keys the provider didn't have access to, users could not verify contacts' identities, and past messages were not secure if the encryption keys were stolen. Telegram's optional secret chat function, which provides end-to-end encryption, received a score of 7 out of 7 points on the scorecard. The EFF said that the results "should not be read as endorsements of individual tools or guarantees of their security", and that they were merely indications that the projects were "on the right track".
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. 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". Nevertheless, they said they saw "no reason why [Telegram] should use a less secure encryption scheme when more secure (and at least as efficient) solutions exist". The Telegram team responded that the flaw does not affect message security and that "a future patch would address the concern".
In April 2016, accounts of several Russian opposition members were hijacked by intercepting the SMS messages used for login authorization. In response, Telegram recommended using the optional two-factor authentication feature. In May 2016, the Committee to Protect Journalists and Nate Cardozo, senior staff attorney at Electronic Frontier Foundation, recommended against using Telegram because of "its lack of end-to-end encryption [by default] and its use of non-standard MTProto encryption protocol, which has been publicly criticized by cryptography researchers, including Matthew Green".
In June 2017, Pavel Durov claimed publicly that U.S. intelligence agencies tried to bribe the company's developers to weaken Telegram's encryption or install a backdoor during their visit to the U.S. in 2016.
Telegram has organized two cryptography contests to challenge its own security. Third parties were asked to break the service's cryptography and disclose the information contained within a secret chat between two computer-controlled users. A reward of respectively US$200,000 and US$300,000 was offered. Both of these contests expired with no winners. Security researcher Moxie Marlinspike and commenters on Hacker News criticized the first contest for being rigged or framed in Telegram's favor and said that Telegram's statements on the value of these contests as proof of the cryptography's quality are misleading.
Telegram was open and working in Iran without any VPN or other circumvention methods in May 2015. 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. According to an article published on Global Voices, these features were being used by Iranians to "share 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". Telegram has 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. In May 2016, the Iranian government asked all messaging apps, including Telegram to move all Iranian users' data to Iranian servers. On 20 April 2017, the Iranian government completely blocked Telegram’s new voice calls, a service that allows individuals to make calls via secure, end-to-end encryption, and keep their conversations private.
In July 2015, it was reported that China blocked access to Telegram Messenger. According to state-owned People's Daily, Chinese human rights lawyers used Telegram to criticize the Chinese Government and the Communist Party of China.
In June 2016, it was found that some ISPs in Bahrain had started to block Telegram. In June 2017 the service faced serious pressure from Russian regulator Roscomnadzor, who tried to force Telegram to get registered in the official telecommunication services roster, which implies serious liability for a registered party. After week-long negotiations and seemed imminent blockage of the service, the conflict ceased after the some high officials having pulled the strings on the regulator. On 14 July 2017, eleven domain name servers related to Telegram were banned by the Indonesian Communication and Information Ministry with the possibility of closing all Telegram applications in Indonesia if Telegram did not make a standard operating procedure to maintain content that was considered unlawful in the apps. In August 2017, Indonesian Government has opened full access of Telegram, after Telegram has made self censorship about negative contents mainly radicalism and terrorism. Telegram said that about 10 channels/groups have been deleted from Telegram everyday due to are categorized as negative contents.
Use by terrorists
In September 2015, in response to a question about the use of Telegram by Islamic State of Iraq and the Levant (ISIS), 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." ISIS has recommended Telegram to its supporters and members and in October 2015 they were able to double the number of followers of their official channel to 9,000. In November 2015, Telegram announced that it had blocked 78 public channels operated by ISIS, which were used for spreading propaganda and mass communication. Telegram stated that it would block public channels and bots that are related to terrorism, but it would not honor "politically-motivated censorship" based on "local restrictions on freedom of speech" and that it allowed "peaceful expression of alternative opinions." Telegram's usage for ISIS's propaganda has reignited the encryption debate and encrypted messaging applications have faced new scrutiny. It has also led to tabloids misunderstanding Telegram as a "jihadi messaging app".
In August 2016, French anti-terrorism investigators asserted that the two ISIS-directed Jihadists who fatally cut the throat of a priest in Saint-Étienne-du-Rouvray in Normandy, France, and videoed the murder, had communicated via Telegram and "used the app to coordinate their plans for the attack". ISIS's media wing subsequently posted a video on Telegram, showing the pair pledging allegiance. A CNN news report stated that Telegram "has become known as a preferred means of communication for the Sunni terror group ISIS and was used by the ISIS cell that plotted the Paris terror attacks in November".
According to Director General of Application and Informatics of the Ministry of Communication and Informatics, Semuel Abrijani Pangerapan, eleven DNS of Telegram was blocked (see sub-section Censorship above) because there are many canals that contain propaganda of radicalism and terrorism, how to assemble bombs, "disturbing images", and other things that are against the Indonesian law.
- Comparison of instant messaging clients
- List of virtual communities with more than 100 million active users
- Internet privacy
- Secure instant messaging
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Images threatening attacks in London and other major world capitals have been posted on jihadi messaging app Telegram
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