LINE Phone number disguised measures that we found out -Weekly ASCII

　A LINE phone that attracted attention as an IP phone with a cheap price.One of the features that other services do not have is that it can be sent with the same phone number as a smartphone that you usually use.However, immediately after the start of the Android version, this number could be disguised (related article).

　While some people are worried, LINE announced on April 5 that it will strengthen security.On April 28, the Android version is version 4.3.Updated to 0 and authentication was enhanced.Following this, the iOS version of the LINE phone started on May 2.It is said that the authentication is performed in the same way as the Android version.

　Then, this version 4.3.What measures were taken in 0?According to LINE's official blog, the following three are confirmed.

・ Confirmation of SIM information of the terminal ・ Confirmation of network connection status ・ Confirmation by illegal examination algorithm

　It may have been a mechanism to check if the terminal has a SIM card or the same as the first authenticated SIM card.If you recognize that it is connected to the network via celluler, it will be possible to determine whether the SIM card has been canceled to some extent.Up to this point, it is almost the same as what I pointed out in the conclusion of the previous article.This is a three -stage measure to enhance security by inserting an illegal detection algorithm here.

　However, the details of the confirmation method and standards have not been disclosed from a security perspective.So I tried to see what kind of action was required to be re -authenticated.

If you pull out the SIM card and send it, it will be not notified

　In the Xperia Z1 (docomo version) used on the main line, I pulled out the SIM card and started and transmitted a LINE phone.The alert was displayed.Without a SIM card, it would not be possible to send a number notification in one shot.In this case, you cannot register only the phone number on the LINE and leave it on the LINE phone, and use the SIM card on another terminal.

It cannot be re -authenticated unless the phone number is linked

　SMS re -authentication is required to cancel a non -notification, but it will not be released unless the phone number originally linked to LINE.If another SIM card is inserted, the SMS will not reach the terminal and cannot be authenticated.However, it is possible to insert the original SIM card into another terminal and only authenticate.

When I inserted the canceled SIM, the phone number was notified and I was able to send it.

　On the other hand, when I pulled out the SIM card and inserted the canceled SIM card, I was able to send the phone number of the SIM card that was inserted first.I tried it several times, but there was no need to re -authenticate the phone number.However, it is unknown how long this condition will last.

　Following the Android version, I tried the same thing on the iPhone version of LINE.

The iPhone has a different number from SIM

　My iPhone 5s was a SIM-free version, and until just before testing, it was stuck with a US T-mobile SIM card.When the LINE phone was sent in this state, the Japanese phone number used for LINE authentication was notified to the other party.Re -authentication was not particularly required, and it could be transmitted by the original SIM phone number different from the SIM that was stabbed at that time.

I was able to notify the number even in the "no SIM" state without the SIM card

　I pulled out the SIM card and sent it out, but it was still not notified.In the first place, the LINE authentication in this iPhone was already done with the au phone number that had already been canceled.

　Unlike Xperia Z1 (and many other Android devices), the iPhone does not restart even if you remove the SIM card.Recognize the newly inserted SIM card without the need to turn off the terminal.I wondered if this specification should not be.

If you restart the iPhone without SIM, you will be in a non -notification state

　So I restarted an iPhone without SIM and started a LINE phone again, and I couldn't notify the phone number.

Even in situations where re -authentication is not possible

　This iPhone LINE requires authentication on au line, but the SIM card has already been canceled.Therefore, the re -authentication has become impossible again.It would be nice if you could authenticate with a new SIM card, but in this case, you have no choice but to delete the app, which is quite inconvenient.

　The following is a guess, but it seems that the restart is a trigger for the LINE phone, and the app side confirms whether there is a SIM card.If you do not restart or insert another SIM card, you may be able to disguise your phone number as before, but you can check under other conditions, such as whether it will lead to a network.There is enough sex.I haven't tried it this time, but it may be that there is a mechanism that generates a certification process after a certain period of time.

　However, the disguise of the phone number can be technically.There is not much need to downside the conditions that require re -authentication.Rather, it would be more important to not be abused even if the standard was published.Also, it may be careful that the hole has not yet been completely blocked, as it may be temporary, but it has been transmitted with the cancelled phone number.On the other hand, the release of the new version was harder to disguise phone numbers than in the beginning.At least it takes a lot of work to find a way out, and it is likely to be a deterrent for abuse.In less than a month, LINE's attitude, which responds to the user's voice quickly, is a point that can be evaluated.

■ Related site LINE Phone Official Blog