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> we want to explore ways for you to communicate with businesses that matter to you too Empty marketing speak, that sentence has zero information content. It j

by Renaud 10y ago

> we want to explore ways for you to communicate with businesses that matter to you too Empty marketing speak, that sentence has zero information content. It just leaves me vaguely worried that they don't seem to be up-front with whatever they are about to do. I'm just glad that FB doesn't have my number and doesn't have access to my contact list.

aembleton 10y ago
If any of your Facebook friends have your number and have synced their contact list, then they do have you number.
- Renaud 10y ago
  But Facebook will not know it's me because FB doesn't have my number. At worst, all FB know is that some people have my Whatsapp number. That doesn't help FB serve targeted ads to my FB account.
  - eric_the_read 10y ago
    FB is constantly popping up a message to me saying, "Is (xxx) xxx-xxxx your phone number? Confirm it now to secure your account" despite the fact that I have never given them my phone #, nor ever used Whatsapp. I'm sure they know perfectly well it's you, they just aren't (for whatever reason) doing anything about it yet.
jamiesonbecker 10y ago
If you've installed WhatsApp, then they do. If I hash your number that you installed whatsapp on and get X, and then hash your number in Facebook and get X, and then realize that X == X, then I just matched your contact list in WhatsApp with all of your data in FB, all without explicitly sharing your phone number. Even better, I now can match up all your friends, and all of their likes and dislikes, and make some educated guesses about what your likes and dislikes are. Hashing, long story short: put some data in, like a phone number, and get a unique, unguessable strong back -- the same string, every time. https://simple.wikipedia.org/wiki/Cryptographic_hash_function https://simple.wikipedia.org/wiki/Cryptographic_hash_functio...
- Renaud 10y ago
  I know what hashing is, but, as I mentioned, FB doesn't have my phone number, so no X hash to compare to whatsapp X hash.
  - deleted 10y ago
    [deleted]

by Renaud 10y ago

aembleton 10y ago

If any of your Facebook friends have your number and have synced their contact list, then they do have you number.

Renaud 10y ago
But Facebook will not know it's me because FB doesn't have my number. At worst, all FB know is that some people have my Whatsapp number. That doesn't help FB serve targeted ads to my FB account.
- eric_the_read 10y ago
  FB is constantly popping up a message to me saying, "Is (xxx) xxx-xxxx your phone number? Confirm it now to secure your account" despite the fact that I have never given them my phone #, nor ever used Whatsapp. I'm sure they know perfectly well it's you, they just aren't (for whatever reason) doing anything about it yet.

jamiesonbecker 10y ago

If you've installed WhatsApp, then they do. If I hash your number that you installed whatsapp on and get X, and then hash your number in Facebook and get X, and then realize that X == X, then I just matched your contact list in WhatsApp with all of your data in FB, all without explicitly sharing your phone number. Even better, I now can match up all your friends, and all of their likes and dislikes, and make some educated guesses about what your likes and dislikes are. Hashing, long story short: put some data in, like a phone number, and get a unique, unguessable strong back -- the same string, every time. https://simple.wikipedia.org/wiki/Cryptographic_hash_function https://simple.wikipedia.org/wiki/Cryptographic_hash_functio...

Renaud 10y ago
I know what hashing is, but, as I mentioned, FB doesn't have my phone number, so no X hash to compare to whatsapp X hash.
- deleted 10y ago
  [deleted]