3 ms·

Hashing something with a limited domain like phone numbers is useless... Does Signal get any benefit out of that hashing at all? Why do they bother?

• tialaramex 6y ago
  For one thing hashing means Signal doesn't care that my telephone number is sixteen digits while yours probably isn't. All the hashes are the same size. In 1975 other users would have cared because that's sixteen digits to painstakingly memorise or copy down somewhere, but that problem went away. Very few people today even notice because who needs telephone numbers? And it's not true that any finite domain is tractable. The IPv6 address space is large enough, and thus sparse enough that it's basically pointless to try to connect to random addresses. If you pick random 32-bit IP addresses and connect to TCP port 22 a lot of them will answer. Some of them might have a bug you know to exploit. Maybe you can get one thousand answers per hour and one in every ten thousand is vulnerable to your attack, you are now successful twice every day. Whereas if you try this with IPv6 you'll die of old age before you connect successfully let alone find a vulnerable server.