Saitama Prefectural Police headquarters (Mainichi/Takuya Suzuki)

       SAITAMA -- An employee from Kanagawa Prefecture was served a fresh arrest warrant by the Saitama Prefectural Police's cybercrime section on July 27 for allegedly interfering with the operation of a company he was asked to work for by making the firm's website inaccessible.

       According to investigators, the 25-year-old man, accused of violating the Act on Prohibition of Unauthorized Computer Access and Obstruction of Business by Damaging a Computer, abused a public key authentication method. According to the Saitama police, it is believed to be the first case in Japan where a person was arrested for unauthorized use of public key authentication.

       The man reportedly accessed the server of a Tokyo-based advertising company operating the firm's website without permission on March 8, 2020, making the website inaccessible for 13 hours.

       The suspect personally undertook work to speed up the company's website as a side business, but apparently had trouble with the company over work content. He has been arrested twice in the past on suspicion of unauthorized access against the company, but has reportedly denied the charges in both cases.

       Public key authentication is a method that uses a pair of digital keys -- a "private key" and a "public key." Investigators say the man connected to the website's server from his own device with the password given to him by the firm. He is said to have arbitrarily set a private key on his device and a public key for the server.

       With public key authentication, it's impossible to access the server from a device on which a private key has not been set. This way of authentication is said to be more secure than a password-based method, and is widely used among research institutes.

       (Japanese original by Ayako Hiramoto and Hayato Narisawa, Saitama Bureau)

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