The main problem with the earlier Tesla keyfobs is that they used a known-broken 40-bit encryption scheme that allowed them to simply be cloned by an attacker.

The main problem with the earlier Tesla keyfobs is that they used a known-broken 40-bit encryption scheme that allowed them to simply be cloned by an attacker. I'm not sure what they fixed other than upgrading the crypto to something that wasn'y horribly insecure. That's also the reason they introduced the PIN feature.