[bvdbijl]

When you install you make a new password by sending an SMS to your phone to verify that you actually own the number.

If you change a SIM card in a phone it will keep using the same Whatsapp number

[sgehlich]

I like the use of the word "password". If they would at least implement a password, the whole thing would be a lot more secure.

[bvdbijl]

They should have made the password random, it's saved anyways.