Before Telegram’s recent problems, institutions like the Kremlin and figures like Iran’s supreme leader, Ayatollah Ali Khamenei, had been among the messaging app’s 200 million users. But Telegram’s increasing popularity prompted scrutiny from countries like France, where investigators found that the app had become a platform for coordinating terrorism.
The growing criticism led Telegram to ban public channels used by the Islamic State. (The channels are one of its distinctive features, allowing messages to be broadcast to an indefinite number of users.) But Mr. Durov and others at Telegram insisted that private messages would remain private.
Here’s more on Telegram’s founder, Pavel Durov
Mr. Durov, the founder of Telegram, is in exile. But not long ago, he was seen as Russia’s Mark Zuckerberg. Now 33, Mr. Durov started a social network, VKontakte, in 2006, when Russia still appeared to have a future as a haven for web freedom. “In some ways, it was more liberal than the United States,” he told The Times almost a decade later, after he chose to leave his country following clashes with the government of President Vladimir V. Putin.
Mr. Durov sold VKontakte, which shared the look and feel of Facebook but was more popular in Russia, and left the country with a reported $300 million in his pocket in 2014. Once abroad, he began Telegram, hoping to offer a service to people who were worried about their privacy.
Since leaving Russia, Mr. Durov has roamed the world with a core team of Telegram engineers, recently spending time in Dubai. Mr. Durov also holds a passport from St. Kitts and Nevis, a nation in the Caribbean.
So, is it totally watertight?
Telegram uses end-to-end encryption, as do WhatsApp and Signal. This type of encryption converts messages into a code without the help of a server in the middle, making it nearly impossible to gain access to communication between two users without their consent.
But Telegram uses its own secure messaging protocol, called MTProto, and the robustness of that system is up for debate. “Nobody quite knows how it works, and a lot of the security analysis that has been done of it suggests that it’s not as secure as some people think it is,” Mr. Woodward said.
The app “has had serious and simple issues in the protocol,” an analysis by researchers at the Massachusetts Institute of Technology found, adding that “any knowledgeable security expert could penetrate” those weaknesses.
Mr. Woodward said that Telegram “also leaks a lot of metadata — so who’s calling whom, when, for how long, that type of thing — which can be just as useful for intelligence organizations.” (Signal, by contrast, is said to retain barely any information on its users.)
Balancing privacy and security
Some of Telegram’s largest user bases are in Iran and Russia — the very countries that have tried to block the app. (Some users in those countries have been using virtual private networks, or VPNs, to hide their geographical location and in that way circumvent restrictions.)
“The jurisdictions that are blocking it are obviously not the liberal Western democracies that are used to allowing people to talk securely,” Mr. Woodward said.
Demonstrations in Russia against the app’s blocking have included prominent opposition figures, including Aleksei A. Navalny, the anti-corruption activist; and Maria Alyokhina, a member of the feminist collective Pussy Riot.
Despite the posturing, Mr. Durov has pushed against making concerns about Telegram a political issue. “I regard myself as a tech entrepreneur,” he told The Financial Times recently, “not as a politician or philosopher.”.