HLR/VLR/AuC

TheHLR (Home Location Register) is a network database that stores andmanages all details of each mobile phone subscriber that is registeredin the corresponding GSM core network. Specifically, the HLR is thelocation register to which an MS identity is assigned for recordpurposes.

The VLR (Visitor Location Register) is a customer database thattemporarily stores subscription information for the visiting customers(called roaming). While the VLR holds information on roaming, it holdsinformation on all customers that use the system at the current timeincluding those at home location.

The AuC (Authentication Center),commonly a part of the HLR, is a protected database that is used in thesecurity data management for the authentication of subscribers. Thesecret key used in each SIM card is stored in the AuC.