Telegram (messaging service)
Telegram is a non-profit cloud-based instant messaging service. Telegram client apps are available 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 running on Android Lollipop
|Developer(s)||Telegram Messenger LLP|
|Initial release||August 2013|
|Platform||Android, iOS, Windows Phone, Windows NT, macOS, Linux, Web platform|
|Available in||13 languages|
|License||GNU GPLv2 or GPLv3 (clients), proprietary (server)|
Telegram was founded by the Russian entrepreneur Pavel Durov. Its client-side code is open-source software but 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. According to its CEO, as of April 2017, Telegram has more than 50% annual growth rate.
Telegram's security model has received notable criticism by cryptography experts. They have argued that it is undermined by its use of a custom-designed encryption protocol that has not been proven reliable and secure, by storing all messages on its servers by default and by not enabling end-to-end encryption for messages by default. Pavel Durov has argued that this is because it helps to avoid third-party unsecure backups, and to allow users to access messages and files from any device. Messages in Telegram are server-client encrypted by default, and the service provides end-to-end encryption for voice calls and optional end-to-end encrypted "secret" chats.
Telegram was launched in 2013 by the brothers Nikolai and Pavel Durov, who had previously founded the Russian social network VK, but had to leave the company after it was taken over by the 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.
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. Pavel Durov has said that the service was headquartered in Berlin, Germany, in 2015 and early 2015, but moved to different jurisdictions after failing to obtain residence permits for everyone on the team. Durov left Russia and is said to be moving from country to country with a small group of computer programmers. According to press reports, Telegram had employees in St. Petersburg. The Telegram team is currently based in Dubai.
In December 2017 Cointelegraph reported, that Telegram was planning to launch a blockchain platform and native cryptocurrency that in January 2018 TechCrunch confirmed, referring to multiple sources,  To fund the TON launch, Telegram is said to be planning an ICO. The platform is said to be based on an entirely new blockchain and may be called the "Telegram Open Network" (TON), while the TON currency may be called "Gram". Telegram plans to raise $3 billion during ICO.
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. In December 2017, Telegram reached 180 million monthly active users.
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. It also accepts online payments with credit cards and Apple Pay. 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.
In February 2018, Telegram launched their social login feature to its users, named as Telegram Login. It features a website widget that could be embedded into websites, allowing users to sign into a third party website with their Telegram account. The gateway sends users' Telegram name, username, and profile picture to the website owner, while users' phone number remains hidden. The gateway is integrated with a bot, which is linked with the developer's specific website domain.
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, 2048-bit RSA 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, some developed by Telegram Messenger LLP and some by the community. Most of them are free and 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||Android 2.3 or later||Yes||GPLv2 or later||Yes||Supports tablets and Android Wear smart watches.|
|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 and Apple Watch.|
|Telegram X||iOS 8.0 or later, Android ||Yes||Proprietary||Yes||An alternative Telegram client written from scratch, with higher speed, slicker animations, themes and more efficient battery use. iOS version is written with Swift.|
|Telegram Messenger||Windows Phone||Yes||GPLv2 or later||Yes|
|Telegram||Firefox OS||Yes||GPLv3||No||Based on Webogram.|
|Telegram Desktop||Windows NT, macOS, and Linux||Yes||GPLv3 with OpenSSL exception||No||Qt-based desktop client. The Windows NT client is a traditional desktop app published in three flavors: With installer, portable, Windows Store app.|
|Telegram||macOS||Yes||GPLv2||Yes||Native macOS client.|
|Telegram||Google Chrome and Chrome OS||Yes||GPLv3||No||Based on Webogram, published on the Chrome Web Store.|
|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.|
|Unigram||Windows 10, Windows 10 Mobile||No||GPLv3||No||A Universal Windows Platform app published on the Microsoft Store.|
|Telegram[third-party source needed]||Ubuntu Touch||No||GPLv2||Yes||Based on TelegramQML.|
|Cutegram||Windows, macOS, and Linux||No||GPLv3||Yes||Based on Qt.|
|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.|
|Telegreat Desktop||Windows, macOS, and Linux||No||GPLv3||No||Based on TDesktop.|
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.
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 the Signal Protocol, which 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 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". Telegram 4.6, released in December 2017, supports MTProto 2.0, which Telegram claims now satisfied the conditions for IND-CCA.
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 register in the official telecommunication services registry, which implies serious liability for a registered party. After week-long negotiations and seeming imminent blockage of the service, the conflict ceased after high officials pulled some strings with 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.
In October 2017, Telegram was inaccessible to users in Pakistan, and as of 17 November 2017, it has been completely blocked as per instructions from PTA, Pakistan's largest ISP, PTCL mentioned this in a tweet to a user.
On December 30, 2017, during anti-government demonstrations across Iran, Telegram has shut down a channel of the Iranian opposition that published calls to use Molotov cocktails against the police, after receiving a complaint from the Iranian government. Pavel Durov explained that the reason for the blocking was a "no calls to violence" policy and confirmed that criticizing local authorities, challenging the status quo and engaging in political debate were seen as "OK" by the platform, while "promoting violence" was not. The opposition group promised to comply with Telegram rules and created a new channel which amassed 700,000 subscribers in less than 24 hours. On December, 31, the Iranian government announced that Telegram has been "temporarily restricted" in order to "ensure calm and security" after the company said it refused to shut down peaceful protesting channels. On January, 13, the app was unblocked by an order of the president Hassan Rouhani, who said that "more than 100,000 jobs had been lost” in Iran as a result of the ban on Telegram. Channels of the opposition remain operational.
Use by terroristsEdit
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 labeling 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 terror group ISIS and was used by the ISIS cell that plotted the Paris terror attacks in November".
In July 2017, Director General of Application and Informatics of the Indonesian Ministry of Communication and Informatics, Semuel Abrijani Pangerapan, said eleven DNS servers of Telegram were blocked (see § Censorship) 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. In August 2017, however, Indonesia lifted the block after countermeasures against negative contents were deployed in association with Telegram LLP.
- "Telegram". Google Play. Retrieved 12 February 2018.
- "Telegram X". Google Play. Retrieved 14 February 2018.
- "Telegram". App Store. Retrieved 4 January 2018.
- "Telegram X". App Store. Retrieved 31 January 2018.
- "Telegram Messenger". Microsoft Store. Retrieved 29 January 2018.
- "Version history". Telegram Desktop. Retrieved 30 December 2017.
- "Telegram". Mac App Store. Retrieved 22 January 2018.
- "Telegram Beta 2 – HockeyApp". rink.hockeyapp.net.
- "Telegram X". Google Play.
- "Telegram-iOS – HockeyApp". rink.hockeyapp.net.
- "Version history". Telegram.
- "Telegram Swift – HockeyApp". rink.hockeyapp.net.
- "Telegram FAQ". telegram.org. Telegram Messenger LLP. Q: Can I translate Telegram?. Retrieved 16 August 2017.
- "List of Telegram applications". 6 February 2014.
- Telegram F.A.Q, "...making profits will never be an end-goal for Telegram."
- Why Telegram has become the hottest messaging app in the world, The Verge. Retrieved 25 February 2014. "Telegram operates as a non-profit organization, and doesn’t plan to charge for its services."
- "Telegram FAQ". 9 August 2015.
- "Latest commits from official repository (Android version)". Github. 10 April 2016.
- "Telegram F.A.Q." Telegram. Retrieved 2017-10-01.
- "Durov's Channel". Telegram. Retrieved 2017-10-01.
- Durov, Pavel (2017-08-14). "Why Isn't Telegram End-to-End Encrypted by Default?". Telegraph. Retrieved 2017-10-01.
- "Why you should stop reading Gizmodo right now". Telegraph. 2017-06-21. Retrieved 2017-10-01.
- "FAQ for the Technically Inclined". core.telegram.org. Retrieved 2017-10-01.
- "Telegram F.A.Q." Telegram. Retrieved 2017-10-01.
- Hakim, Danny (2 December 2014). "Once Celebrated in Russia, the Programmer Pavel Durov Chooses Exile". The New York Times. Retrieved 19 November 2015.
- Shu, Catherine (27 October 2013). "Meet Telegram, A Secure Messaging App From The Founders Of VK, Russia's Largest Social Network". TechCrunch. Retrieved 18 March 2016.
- "Russia's Zuckerberg launches Telegram, a new instant messenger service". Reuters. 30 August 2013. Retrieved 18 March 2016.
- "Telegram - Android Apps on Google Play". play.google.com. Retrieved 19 November 2015.
- "Telegram Messenger on the App Store". App Store. Retrieved 19 November 2015.
- Thornhill, John (3 July 2015). "Lunch with the FT: Pavel Durov". Financial Times. Retrieved 19 November 2015.
- Brandom, Russell (6 October 2014). "Surveillance drives South Koreans to encrypted messaging apps". The Verge. Retrieved 19 November 2015.
- Turton, William (29 September 2017). "What isn't Telegram saying about its connections to the Kremlin?". The Outline. Retrieved 11 October 2017.
- "This $5 Billion Encrypted App Isn't for Sale at Any Price". Bloomberg. 12 December 2017. Retrieved 22 December 2017.
- "Exclusive: Telegram to Release Blockchain Platform, Native Cryptocurrency". Cointelegraph. 22 December 2017.
- Butcher, Mike. "Telegram plans multi-billion dollar ICO for chat cryptocurrency". TechCrunch. Retrieved 2018-01-12.
- "Telegram Open Network ICO". icoarray.com. Retrieved 2018-01-25.
- Telegram Hits 35M Monthly Users, 15M Daily With 8B Messages Received Over 30 Days, TechCrunch, 24 March 2014
- Telegram Reaches 1 Billion Daily Messages, Telegram, 8 December 2014
- Telegram Hits 2 Billion Messages Sent Daily, Telegram, 13 May 2015
- Lomas, Natasha (21 September 2015). "Telegram Now Seeing 12BN Daily Messages, up From 1BN in February". Techcrunch. Retrieved 19 November 2015.
- Burns, Matt (23 February 2016). "Encrypted Messaging App Telegram Hits 100M Monthly Active Users, 350k New Users Each Day". TechCrunch. Retrieved 23 February 2016.
- Lopez, Miguel, Configurando Telegram en el iPhone, en la web y en el Mac [Configuring Telegram in the Apple iPhone, the Web and the Mac] (in Spanish), Applesfera, retrieved 4 December 2014
- Munizaga, Jonathan (1 December 2014). "Telegram ya permite migrar conversaciones y contactos a una línea nueva" [Telegram already allows migrating conversations and contacts to a new line] (in Spanish). Wayerless. Retrieved 2 December 2014.
- Mateo, David G (1 December 2014). "Telegram ahora permite traspasar mensajes al cambiar de número" (in Spanish). TuExperto. Retrieved 2 December 2014.
- "Secure Messaging App Telegram Adds Usernames And Snapchat-Like Hold-To-View For Media". Techcrunch. 23 October 2014. Retrieved 23 October 2014.
- "Hiding Last Seen Time - Done Right". Retrieved 18 May 2017.
- Kirk, Jeremy (15 January 2015). "How much trust can you put in Telegram messenger?". PC World. IDG. Retrieved 4 May 2016.
- Rad, Alex (9 January 2015). "A 264 Attack On Telegram, And Why A Super Villain Doesn't Need It To Read Your Telegram Chats". alexrad.me (Blog). Retrieved 4 May 2016.
- Lokot, Tetyana (2 May 2016). "Is Telegram Really Safe for Activists Under Threat? These Two Russians Aren't So Sure". Advox. Global Voices. Retrieved 4 May 2016.
- Menn, Joseph; Torbati, Yeganeh (2 August 2016). "Exclusive: Hackers accessed Telegram messaging accounts in Iran - researchers". Reuters. San Francisco/Washington: Thomson Reuters. Retrieved 3 August 2016.
- Lipp, Sebastian; Hoppenstedt, Max (26 August 2016). "Exklusiv: Wie das BKA Telegram-Accounts von Terrorverdächtigen knackt". Motherboard (in German). Vice Media Inc. Retrieved 28 August 2016.
- "Group chats on Telegram can now have up to 1,00,000 members. Admins can use advanced permissions and butler bots to keep the peace". 23 October 2017 – via Twitter.com.
- Unsend Messages, Network Usage, and More, Telegram, 3 January 2017, retrieved 4 April 2017
- "How secure is Telegram?", FAQ, Telegram
- Telegram Bot Platform, Telegram, 24 June 2015, retrieved 1 September 2015
- "Payments for Bots". Telegram. Retrieved 2018-02-12.
- Schellevis, Joost (23 July 2015). "Telegram-bots kunnen relatief ongemerkt meelezen in groepsgesprekken". Tweakers (in Dutch). Retrieved 25 October 2015.
- Introducing Inline Bots, Telegram, 4 January 2016, retrieved 4 April 2017
- Lobao, Martim (22 September 2015). "Telegram v3.2 Brings Channels For Broadcasting Your Messages To The World". Android Police.
- Telegram Stickers, Telegram, 2 January 2015, retrieved 5 January 2016
- Drafts, Picture-in-Picture, and More, Telegram, 14 June 2016, retrieved 4 April 2017
- "FAQ for the Technically Inclined". Telegram. Retrieved 9 January 2016.
- Description of MTProto Mobile Protocol, Telegram
- Rottermanner et al. 2015, p. 2
- Hamburger, Ellis (25 February 2014). "Why Telegram has become the hottest messaging app in the world". The Verge. Vox Media. Retrieved 17 March 2016.
- Rottermanner et al. 2015, p. 6
- Perfect Forward Secrecy, Telegram, 14 December 2014
- "Github issue 871: missing secret chats". 2 July 2015. Retrieved 25 July 2017.
- Franceschi-Bicchierai, Lorenzo (24 February 2015). "Encryption Fails: When to Freak Out and When to Chill". Motherboard. Vice Media. Retrieved 9 January 2016.
- Voice Calls: Secure, Crystal-Clear, AI-Powered, Telegram, 30 March 2017, retrieved 3 April 2017
- "Telegram Login for Websites". Telegram. Retrieved 2018-02-12.
- "Telegram 4.8 arrives with Telegram Login and streaming". Neowin. Retrieved 2018-02-12.
- "Telegram, el chat que compite con Whatsapp" [Telegram, the chat that competes with WhatsApp]. El País (in Spanish). UY. Retrieved 8 January 2016.
- Rull, Antonio (2 February 2014). "Pavel Durov, creador de Telegram: "Ninguna aplicación es 100% segura"" [Pavel Durov, creator of Telegram: "No application is 100% safe"]. eldiario.es (in Spanish). Retrieved 12 February 2014.
- "Telegram Apps". Telegram.org. Retrieved 9 January 2016.
- DrKLO. "DrKLO/Telegram". GitHub. Retrieved 8 January 2016.
- "Telegram-Anleitung: So benutzt man den Messenger" (in German). Newsslash.
- "Telegram se actualiza con compatibilidad para Android Wear" [Telegram updated with Android Wear compatibility] (in Spanish). Sevilla: ABC. Retrieved 7 December 2014.
- peter-iakovlev (18 November 2015). "peter-iakovlev/Telegram". GitHub. Retrieved 8 January 2016.
- "Telegram se actualiza para la pantalla del iPad" [Telegram updated for the iPad screen] (in Spanish). Cnet.
- cpy, Mujeeb (23 January 2018). "Telegram X for Android Released – What's New". IB Computing. IB Computing. Retrieved 23 January 2018.
- "Telegram X: Progress through Competition". telegram.org. Telegram LLC.
- Igor Zhukov. "zhukov/webogram". GitHub. Retrieved 8 January 2016.
- telegramdesktop. "telegramdesktop/tdesktop". GitHub. Retrieved 8 January 2016.
- overtake (1 December 2015). "overtake/telegram". GitHub. Retrieved 8 January 2016.
- vysheng. "vysheng/tg". GitHub. Retrieved 9 January 2016.
- danog. "danog/MadelineProto". GitHub. Retrieved 25 August 2017.
- "Unigram Preview - Microsoft Store". Microsoft Store. Retrieved 2017-04-20.
- "UnigramDev/Unigram". GitHub. Retrieved 2017-04-20.
- "Telegram app". Launchpad.
- "Telegram App in Launchpad".
- Sauerland, Andreas (21 March 2015). "Cutegram: So verwenden Sie die Chat-App am PC". Computer Bild (in German). Axel Springer. Retrieved 25 April 2016.
- Aseman Land. "Aseman-Land/Cutegram". GitHub. Retrieved 8 January 2016.
- Aseman Land. "Cutegram". Aseman. Retrieved 8 January 2016.
- "Telegram app". OpenRepos.
- "majn/telegram-purple". GitHub. Retrieved 2016-09-30.
- "Sea-n/tdesktop". GitHub. Retrieved 2018-02-13.
- Roble, Patricio (3 March 2014). "Can Telegram Beat WhatsApp with a Public API?". ProgrammableWeb.
- King, Bertel (27 February 2015). "WhatsApp+ Developer Releases Telegram+ After Being Forced To Drop The First Project". AndroidPolice.
- "WhatsApp+ Is Now Officially Dead After Receiving A Cease And Desist From The Real WhatsApp". Android Police. 21 January 2015.
- "Socializer Messenger App Offers a New Approach to Messaging". 14 September 2015.
- Carter, Eric (27 June 2015). "Telegram Launches Bot API and Platform". ProgrammableWeb.
- Butcher, Mike (24 June 2015). "Telegram's New Platform Lets Developers Create Smart Message Bots With Multiple Uses". TechCrunch.
- Ubpin, Bruce (23 February 2016). "Introducing The Forbes Newsbot on Telegram". Forbes.
- Bernard, Travis (15 March 2016). "Check out the new AI-powered TechCrunch news bot on Telegram messenger". TechCrunch.
- "Why Telegram's security flaws may put Iran's journalists at risk". Committee to Protect Journalists. 31 May 2016. Retrieved 20 July 2016.
- Jakobsen & Orlandi 2015
- Cox, Joseph (10 December 2015). "Why You Don't Roll Your Own Crypto". Motherboard. Vice Media. Retrieved 11 December 2015.
- Turton, William (19 November 2015). "Cryptography expert casts doubt on encryption in ISIS' favorite messaging app". The Daily Dot. Retrieved 11 December 2015.
- "Snowden doubts security of Telegram". RT. RT. 20 December 2015. Retrieved 11 February 2017.
- Turton, William (24 June 2016). "Why You Should Stop Using Telegram Right Now". Gizmodo. Gawker Media. Retrieved 7 July 2016.
- Sawers, Paul (30 June 2016). "Ahead of IPO, mobile messaging giant Line introduces end-to-end encryption by default". VentureBeat. Retrieved 10 September 2016.
- "WhatsApp und Alternativen: Datenschutz im Test" [WhatsApp and alternatives: data protection tested]. Stiftung Warentest (in German). 26 February 2014. Retrieved 2 March 2016.
- "Secure Messaging Scorecard". Electronic Frontier Foundation. 17 February 2015. Retrieved 20 July 2016.
- Jakobsen & Orlandi 2015, p. 6
- Jakobsen & Orlandi 2015, p. 1
- "FAQ for the Technically Inclined: What about IND-CCA?". Telegram. Telegram. Retrieved 25 March 2017.
- Clary, Grayson. "The Flaw in ISIS's Favorite Messaging App". The Atlantic. The Atlantic. Retrieved 25 March 2017.
- "FAQ for the Technically Inclined". Telegram. Telegram. Retrieved 9 December 2017.
- "Telegram founder: U.S. intelligence agencies tried to bribe us to weaken encryption". FastCo News. 15 June 2017. Retrieved 15 June 2017.
- Leyden, John (14 June 2017). "Telegram chat app founder claims Feds offered backdoor bribe". The Register. Situation Publishing. Retrieved 15 June 2017.
- "Winter Contest Ends". Telegram. 2 March 2014. Retrieved 24 October 2015.
- "Crypto Contest Ends". Telegram. 11 February 2015. Retrieved 24 October 2015.
- Marlinspike, Moxie (19 December 2013). "A Crypto Challenge for the Telegram Developers". Thought Crime. Retrieved 2 March 2014.
- Wauters, Robin (19 December 2013). "Cracking contest: first one who breaks Telegram gets $200,000 in bitcoins (but really, nobody wins)". Tech.eu. Retrieved 2 March 2014.
- Hornby, Taylor (19 December 2013). "Telegram's Cryptanalysis Contest". Crypto Fails. Retrieved 24 October 2015.
- "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.
- Alimardani, Mahsa (28 August 2015). "Is Telegram's Compliance with Iran Compromising the Digital Security of Its Users?". Global Voices Online. Retrieved 30 August 2015.
- "Telegram FAQ". Telegram. Retrieved 14 September 2015.
- Dillet, Romain. "Iran forces messaging apps to move data to Iranian servers". TechCrunch. Retrieved 31 May 2016.
- "Iranian Judiciary Blocks Popular Telegram App's New Voice Call Service – Center for Human Rights in Iran". www.iranhumanrights.org. Retrieved 1 February 2018.
- "China blocks Telegram messenger, blamed for aiding human rights lawyers - Hong Kong Free Press HKFP". 13 July 2015. Retrieved 1 February 2018.
- "Leading Bahraini ISPs are Blocking Telegram Traffic". Bahrain Watch. 2016-06-28. Retrieved 2017-08-08.
- Boy Riza Utama (July 15, 2017). "Tak Perlu Blokir Telegram, Pengamat Sarankan Cara Ini kepada Mekominfo".
- "Telegram Setiap Hari Hapus 10 Grup Di Indonesia Terkait Konten Radikal dan Terorisme". August 10, 2017.
- "Telegram, the Secure Alternative to Whatsapp, is Down in Pakistan". 2017-10-24. Retrieved 2017-11-18.
- "Telegram Blocked in Pakistan!". 2017-11-17. Retrieved 2017-11-18.
- ""Telegram is shutting down a channel that called for violent protests against Iran's government"". December 30, 2017.
- "Twitter conversation between Nariman Gharib and Pavel Durov". December 31, 2017.
- ""Iran restricts social media and issues stern warning to protesters"". December 31, 2017.
- "Iran Unblocks Widely Used Messaging App Telegram After Two Weeks – Center for Human Rights in Iran". www.iranhumanrights.org. Retrieved 2018-01-16.
- Lomas, Natasha. "Telegram Now Seeing 12BN Daily Messages, Up From 1BN In February". TechCrunch. Retrieved 19 November 2015.
- Haddad, Margot; Hume, Tim. "Killers of French priest met 4 days before attack". cnn.com.
- Zavolokyn, Gennady. "Павел Дуров прокомментировал для CNN историю с подготовкой теракта через Telegram". TJournal.ru (in Russian). Retrieved 20 October 2015.
- Steve Ragan (16 November 2015). "After Paris, ISIS moves propaganda machine to Darknet". CSO Online.
- "Isis Telegram channel doubles followers to 9,000 in less than 1 week". Yahoo News. 12 October 2015.
- "Encrypted messaging app Telegram shuts down Islamic State propaganda channels". Telegraph.co.uk. Retrieved 19 November 2015.
- "One app maker has shut down almost 80 secret channels used by ISIS to communicate". Business Insider. Retrieved 19 November 2015.
- "Telegram founder knew Isis used the app to communicate before Paris attacks". The Independent. 2015-11-20. Retrieved 2017-04-24.
- "Secretive messaging app used by IS takes down posts". CNBC. Retrieved 19 November 2015.
- Sanger, David; Perlroth, Nicole (16 November 2015). "Encrypted Messaging Apps Face New Scrutiny Over Possible Role in Paris Attacks". The New York Times. Retrieved 19 November 2015.
- Foges, Clare. "Why is Silicon Valley helping the tech-savvy jihadists?". The Telegraph. Retrieved 9 December 2015.
- Campbell, Scott (26 July 2016). "ISIS warn London 'next to be attacked' as UK churches put on terror alert after French priest murder". Daily Mirror. Retrieved 15 December 2016.
Images threatening attacks in London and other major world capitals have been posted on jihadi messaging app Telegram
- (in Russian) Martynov, Kirill. "Занять Телеграм". Novaya Gazeta. Retrieved 26 June 2017.
- Widiartanto, Yoga Hastyadi (14 July 2017). "Ini Alasan Pemerintah Blokir Telegram" [This is the Reason Why the Government Blocks Telegram]. Kompas (in Indonesian). Retrieved 15 July 2017.
- "Indonesian government lifts ban on messaging service Telegram". The Straits Times. SPH Digital News. 11 August 2017.
- Jakobsen, Jakob; Orlandi, Claudio (8 December 2015). "On the CCA (in)security of MTProto" (PDF). Cryptology ePrint Archive. International Association for Cryptologic Research (IACR). Retrieved 11 December 2015.
- Rottermanner, Christoph; Kieseberg, Peter; Huber, Markus; Schmiedecker, Martin; Schrittwieser, Sebastian (December 2015). Privacy and Data Protection in Smartphone Messengers (PDF). Proceedings of the 17th International Conference on Information Integration and Web-based Applications & Services (iiWAS2015). ACM International Conference Proceedings Series. ISBN 978-1-4503-3491-4. Retrieved 18 March 2016.