SIM's use a derived key - which means that getting your hands on that key would only affect that specific SIM, and generally the Km (master key) exists only on

SIM's use a derived key - which means that getting your hands on that key would only affect that specific SIM, and generally the Km (master key) exists only on an HSM. There's not much point in the intelligence services going after these keys, if they can just put a box in the operator's data center and capture unencrypted traffic