- Joined
- Jun 12, 2020
They're way cooler than that. They have a tiny processor and do cryptographic challenges with the tower to establish a session. I'm not entirely sure how eSIM modules work, but it's probably a programmable SIM in software where you can write the cryptographic secrets to a protected area and do the same challenge-response authentication.The sim card is essentially just a config file that the phone reads in, so having that extra hardware for no reason is an extra point of failure.
One notable oddity associated with eSIMs I came across recently is reflashing your phone does not wipe out eSIMs. After I went back to CalyxOS, all my previous eSIMs were still listed and worked fine. This is likely due to that protected area being entirely unaffected by the OS itself being replaced.