Strictly speaking, IMSI identifies the SIM. A subscriber may have multiple SIMs and many SIMs throughout their lifetime. The IMSI is never ever transferable. Th

Strictly speaking, IMSI identifies the SIM. A subscriber may have multiple SIMs and many SIMs throughout their lifetime. The IMSI is never ever transferable. The IMSI/SIM represents a unique network identity and links to items such as individualised cryptographic keys; session state, etc. the counterparts to which are baked into the SIM itself.