26 September

If your number is saved in someone else's contacts, their LINE app may add you as a friend automatically, because apps send the numbers in a user's address book to their servers for matching. On 26 September 2017, Signal published a new way to do this matching without its servers learning what the address book contains. In the same post, Signal explained that uploading phone numbers as hashes (codes that hide the original number) does not protect them, because there are so few possible numbers that the hashes can almost always be reversed. In February 2024 Signal added a setting that stops people from finding you by your number, and its Android beta in September 2026 lets you register without a phone number at all (see Phone-number-free registration in the Signal Android beta). On LINE, you can stop people who know your number from adding you by turning off the setting under Settings > Friends that allows others to add you.