(CNN) The founder of an encrypted app favored by ISIS militants says opening a "back door" in to such communications tools could aid terrorists and criminals.

And that secrecy means it has developed a reputation as one of the go-to tools for terrorists -- an image the black-clad Durov is keen to dispel, pointing out that most of his app's 100 million users are ordinary people.

"In America they started to refer to Telegram as 'ISIS's preferred messaging app,'" he says. "But in reality there are many more legitimate users."

But Durov insists that the "overly simplistic solutions" suggested by intelligence services, blocking access to apps and allowing governments to break in to secure communications are not the answer.

Private data at risk

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"When you look into them you realize they wouldn't work and they would actually make the situation worse," he says. "Essentially they want companies providing encrypted messaging services to implement 'back door' solutions."

The problem with that approach, he says, is that you cannot make messaging technology secure for everybody except terrorists. "You cannot make it safe against criminals and open for governments. It's either secure or not secure," he said.

"If such a measure is implemented, most of our correspondence, our business secrets, our private data would be put at risk. Because if there's a back door, not only a government official could use it, but theoretically criminals including terrorists [could too]."

Durov says a number of governments -- including that of Britain -- have reached out to him for help in the past, but encryption means that even he can't access his users' messages.

"For two and a half years of our existence we haven't disclosed a single bite of data of our users," he says proudly.

That's good news for anyone who wants to communicate without being spied on -- whoever they may be.

Those behind the Paris attacks used apps including Telegram and WhatsApp. But, investigators say, it's not known whether those apps were used to hide their plotting. ISIS later used the service to claim responsibility for the massacres.

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A source with knowledge of the Paris investigation told CNN that what had been said through the attackers' encrypted messages may never be known.

Following the Paris attacks, there were growing calls for regulation of encrypted technology, which FBI Director James Comey said was "at the center of terrorist trade craft."

Durov, Telegram's founder, dismisses the suggestion Telegram is in any way responsible for the carnage at the Bataclan and other sites across Paris, in which 130 people died.

"I don't think so," he says. "They were probably using other messaging services as well. It's misleading to say that we were responsible -- or any tech company is responsible -- for that."

Darker side of technology

The fact that his app is used by ISIS fighters and propagandists is, he says, "the darker side of technology in general."

"Whenever technological advancement is made it can always be used both for good or for bad," he said.

"You can compare it with the invention of gunpowder for example: Once the secret is out there, it doesn't make sense to force your local users of gunpowder to make your gunpowder less efficient when the other side can still use it and use it in an efficient way.

"The same thing applies to messaging apps: Terrorists will always find a way to communicate. They will always find a solution," he believes.

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Telegram has stepped in to shut down public channels on its app that were being used by ISIS -- at the last count, the company says they have had closed more than 660 of them.

"Every day four or five channels are reported by our users and we take them down," Durov explains.

Durov is originally from Russia, but since going into exile in 2014 he says he has had no permanent home; instead he's opted to move from city to city, traveling light.

His experiences in his native land sparked the decision to create Telegram, and also shaped his view of the importance of privacy and freedom from monitoring by the state, which says they are monitoring criminal activity like drug dealing, human trafficking and pedophiles.

Risks vs. rights

"When I was living in Russia a few years ago, all these activities were used as a pretext to monitor the communication of Russian citizens and then in many cases used to suppress dissidents and liberal thinking individuals," he said.

For Durov, it's a question of balancing priorities: the right to communicate without being snooped on, versus the chance of preventing a possible attack -- and he insists that's not a decision he should be making.

"This is a big debate concerning the values of the society in question: Whether the risk of a terrorist act is more important than the 100% right to privacy," he says. "This should be decided by the people of the country in question. Not by myself."

But he warns that making a choice against privacy would likely open a Pandora's Box of trouble: "For me I would say that in most parts of the world this would lead to dangerous consequences."