How to find the owner of lost AirPods using only the last four digits of a phone number?
Apple's wireless earphones,
Did you lose your AirPods? | Alex Yancey
https://alexyancey.com/lost-airpods/
One day, Yancey's friend found a pair of AirPods lying on the ground. When he brought his smartphone close to the AirPods and tapped the notification that appeared, the serial number of the AirPods and the last four digits of the phone number were displayed, but since he couldn't contact the owner with that alone, his friend asked Yancey for help.
The following image shows the information displayed on Yancey's friend's smartphone. In this case, the last four digits of the phone number are provisionally set to '1234.'
One way to find the owner is to send an SMS message to all combinations of phone numbers with the last four digits '1234' saying 'Did you drop your AirPods?' However, this is an unrealistic method because the number of people to contact is too large. Therefore, considering that the place where the AirPods were picked up is Portland, Oregon, one of the largest cities in the northwestern United States, Yancey first assumed that 'the owner lives near his or her address in Portland.'
American phone numbers are standardized to 10 digits consisting of a combination of a 3-digit area code and a 7-digit unique number, and unlike Japan, there is no distinction between landlines and mobile phones. In other words, in Japan, if you see a number starting with '090' or '080', you can tell that it is a mobile phone number, but in America, you cannot tell just by looking at a phone number whether it is a landline or a mobile phone, but instead you can tell 'what area the person lives in'.
Yancey's assumption that the owner of the lost AirPods lives near their address allows them to determine the first three digits of the area code. Then, they know the three-digit area code and the last four digits of the 10-digit number, so the remaining combinations of phone numbers are 1,000 combinations with the middle three digits ranging from '000' to '999'. This makes it quite realistic to send SMS messages to everyone, but Yancey wanted to narrow it down a bit more.
In fact, in Portland, the middle three digits of a phone number, '000' to '199', are reserved codes that cannot be used by telecommunications carriers. In addition, the middle three digits are assigned to wireless communication carriers, including mobile phones, and only 26% of the total are assigned to wireless communication carriers. This reduced the number of possible phone number combinations to 232.
In addition, since the chances of Android users using AirPods are quite low, we can assume that the owner has an iPhone. So Yancey used an API that can check whether the phone number is compatible with Apple's messaging service iMessage to eliminate phone numbers that are not used by iPhones. In the end, he was able to narrow down the number of phone numbers that could be the owner of the AirPods to 84.
Once he had narrowed down the list of phone numbers, Yancey used a script on his MacBook to send a mass iMessage to those numbers. He got fewer than 10 replies, including one person who said they'd lost their AirPods. Yancey provided that person's contact information to a friend, who was then able to return the lost AirPods to their owner.
This method has also become a hot topic on the social news site Hacker News, with people sharing their experiences such as, 'I dropped my AirPods in their case on the school playground, and even a week later, after heavy rain , they still had charge left and I was able to find them using the Find My feature,' and 'I put my AirPods in their case through the washer and dryer without breaking them.'
Did you lose your AirPods? | Hacker News
https://news.ycombinator.com/item?id=41334207
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in Web Service, Hardware, Posted by log1h_ik