Photo/Illutration Users of the Telegram social media app can set the time they want a message automatically deleted. (Ryo Oyama)

A social media app developed in Russia to skirt censorship there is proving to be the biggest roadblock for Japanese police investigating a recent string of scams and deadly robberies.

The four ringleaders the Philippines deported to Japan earlier this month apparently used the Telegram app to send instructions to their underlings in Japan who carried out the actual crimes, including the suspected brutal murder of a 90-year-old woman in Komae, western Tokyo.

Telegram is a free app that can be used to send messages and videos. The service has about 700 million users around the world, according to its official website.

Telegram has a secret chat function that lets users set the time when a message is automatically deleted from the sender's and the recipient’s devices. Records of the encrypted messages are not left in the computer system of the service provider.

That may be one reason many of the 15 or so mobile phones and tablet computers sent to Japanese police by their Philippine counterparts had almost no relevant data in them, police said.

It is not clear if the devices were rebooted or if the messages were automatically deleted through the secret chat function. The instructions were sent by individuals using names such as "Luffy" and "Kim."

The Telegram app was developed by a Russian who was pressured by authorities to delete anti-government posts on another social media site operated by the developer, according to cybersecurity expert Koichiro Komiyama.

To avoid interference from the authorities, Telegram included several functions intended to protect freedom of expression as well as the privacy of the user.

Many of the instructional messages sent to those who carried out the crimes in Japan had been deleted, making it difficult for Japanese police to determine the exact chain of command.

Daisuke Tanaka, 48, is president of Asueito Advisory Inc., a company that analyzes electronic equipment.

He said it is extremely difficult to analyze Telegram because the company has not made its encryption procedure open, nor has it revealed the location of the computer system used to operate the service.

“Because an anti-authority thinking lies at the root of the service, the operator will not likely cooperate with investigators,” Tanaka said.

But at the same time, Tanaka said it is not impossible to reconstruct deleted messages.

He said it is possible to partially reconstruct messages, determine the sender and the time it was sent if the analytical tool used is compatible with the device and its operating system.

Tanaka said there is a much greater chance of obtaining messages to use as evidence if the sender forgot to utilize the secret chat function.

Investigative sources said any analysis would likely take time because the 15 or so devices sent to Japan from the Philippines span a wide range of models and different app versions, meaning different methods would have to be used for each device to reconstruct deleted messages.

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