4 ms·
For the purposes of entropy, you need only consider 10 valid choices for each symbol of a phone number so it's closer to 33.21 bits (10 * (log(10) / log(2))) an
by ZephyrP 6y ago
For the purposes of entropy, you need only consider 10 valid choices for each symbol of a phone number so it's closer to 33.21 bits (10 * (log(10) / log(2))) and smaller still when discarding impossible area, trunk & subscriber numbers.
- gpvos 6y agoAnd then a bit larger again when including foreign phone numbers.
- kosievdmerwe 6y agoSo given than 80 bits is much bigger than 30-40 bits, if I know someone's hash I can very easily narrow down their phone number to one or sometimes two candidates.
- tialaramex 6y agoNo, I'm describing the truncated hash. Signal truncates SHA1 to 10 bytes of output. No matter if your phone number is six digits or sixteen, Signal uses 10 bytes (80 bits) of the hash.