3 ms·
Unless you know the original algorithm, any collisions you find are useless. I'll give you an example. Here's a hashcode from a real phone number: 178688367191
by xapata 10y ago
Unless you know the original algorithm, any collisions you find are useless.
I'll give you an example. Here's a hashcode from a real phone number: 1786883671916465751. What's the phone number I used to generate it?
- lorenzhs 10y agoPretty sure Facebook can find out which hash function WhatsApp is using.
- xapata 10y agoOr they can just get the original data... So why complain that hashing is insecure?
- JshWright 10y agoWith one hash, that would obviously be impossible. With millions? Trivial... Particularly when you already know the phone numbers for many of the users (those who have added their number to their profile), and you can match against contact databases.
- xapata 10y agoIf you're going to cheat by using your contacts database, why not just ask your colleague for the original data? Even with hundreds of millions of observations, the space of possible hashing algorithms that map phone numbers onto those hash codes is infinite. Well, not infinite, but the space of functions that map phone numbers onto whatever domain the hash codes have is mind bogglingly large.