« There’s a concept in encryption called perfect forward secrecy. This is a property of some encryption protocols that keeps past communication secret, even if their private keys are compromised. I think of the modern internet as having perfect forward vulnerability - once your information gets out, there’s no way to make it private again. »
https://robertheaton.com/2017/11/24/identity-graphs-how-online-trackers-follow-you-across-devices/