Section: C.1.1.3 Time-based sequence number generation
Content: In its binary representation, the sequence number consists of two concatenated parts SQN = SEQ || IND. The part SEQ is not divided into two parts. The global counter GLC is thus as long as SEQ. Instead of storing the individual counter SEQHE in the HE there is a value DIF stored in the HE which is individual for each user. The DIF value represents the current difference between generated SEQ values for that user and the GLC. When the HE needs new sequence numbers SQN to create new authentication vectors, HE retrieves the (user-specific) value of DIF from the data base and calculates SEQ values as SEQ = GLC +DIF. The DIF value may have to be updated in the HE only during the re-synchronization procedure. In this case the DIF value is set as DIF = SEQMS - GLC where SQNMS = SEQMS || INDMS is the value sent by USIM in the re-synchronization procedure.