Ciphering

 Ciphering:

It changes the contents of eight interleaved blocks by using the encryption methods that are known to the Mobile Station (MS) and the Base Transceiver Station (BTS).

Must Read>> Base Transceiver Station (BTS)

In order to enhance security, different encryption algorithms are used for different calls.

In GSM there are two ciphering algorithms A3 and A5. These algorithms are used to prevent unauthorized network access and radio transmission privacy.

The A3 algorithm provides authentication to each mobile by verifying the passcode with the SIM with a cryptographic key at the Mobile Service Centre (MSC).

The A5 algorithm provides scrambling of 114 coded data bits that are sent in each time slot.