2 ms·
Sure, there are hashing functions, but with a search space that is as small as a 10 digit phone number it is easy to create rainbow tables that covers them all.
by Tepix 4y ago
Sure, there are hashing functions, but with a search space that is as small as a 10 digit phone number it is easy to create rainbow tables that covers them all.
Signal has spent some time thinking about this problem, see https://signal.org/blog/private-contact-discovery/ https://signal.org/blog/private-contact-discovery/
- wuiheerfoj 4y agoMultiple hashing rounds or bcrypt would likely be a fine solution for this
- eps 4y agoPray tell the details.
- MonkeyClub 4y agoYeah I initially thought as GP, perhaps some salting, hence my comment above. But the only salt worth its salt (sorry, had to) would be the number itself. Otherwise, you’d need a database associating the number with its salt. And if you use the number itself as the salt, then rainbow tables it is.
- Tepix 4y agoEven if you tweak your hashing algorithm to take 1 second on a fast CPU, you get 31 years of CPU time to search the entire space. That's simply not enough! And going beyond 1 second is probably also not practical.
- deleted 4y ago[deleted]