Telegram (messaging service)

Telegram (messaging service)


Telegram is a free cloud-based instant messaging service. Telegram clients exist for both mobile (Android, iOS, Windows Phone, Ubuntu Touch) and desktop systems (Windows, macOS, Linux).[10] 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.[11] Its client-side code is open-source software, 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 argued 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 terrorist organization Islamic State.



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.[75][76][77] It has also been suggested that Telegram did not employ developers with sufficient expertise or credibility in this field.[78]

Critics have also disputed claims by Telegram that it is “more secure than mass market messengers like WhatsApp and Line“,[36] 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.[79][75][80] Since July 2016, Line has also applied end-to-end encryption to all of its messages by default.[81]

On 26 February 2014, the German consumer organisation Stiftung Warentest 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 servers 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.[82]

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.[83] 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”.[83]

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.[84] 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”.[85]

In April 2016, accounts of several Russian opposition members were hijacked by intercepting the SMS messages used for login authorization.[31] In response, Telegram recommended using the optional two-factor authentication feature.[31] 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“.[75]

Cryptography contests

Telegram has organised 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.[86][87] 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.[88][89][90]


Telegram was open and working in Iran without any VPN or other circumvention methods in May 2015.[91] 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.[92] 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”.[92] 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.[93] In May 2016, the Iranian government asked all messaging apps, including Telegram to move all Iranian users’ data to Iranian servers.[94]

Use by terrorists

In September 2015, in response to a question about the use of Telegram by Islamic State of Iraq and the Levant, 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.”[95] ISIS has recommended Telegram to its supporters and members[96][97][98] and in October 2015 they were able to double the number of followers of their official channel to 9,000.[99] In November 2015, Telegram announced that it had blocked 78 public channels operated by ISIS, which were used for spreading propaganda and mass communication.[100][101] 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.”[102] Telegram’s usage for daiish’s propaganda has reignited the encryption debate and encrypted messaging applications have faced new scrutiny.[103][104]

In July 2016 a tabloid journalist branded Telegram a “jihadi messaging app”.[105]

In August 2016, French anti-terrorism investigators asserted that the two daiish-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”. daiish’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 daiish and was used by the daiish cell that plotted the Paris terror attacks in November“.[96]


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