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random number (RAND)

The random number (RAND) is used to check the subscriber's network access authorization in GSM networks

. The generation of a random number is based on a cryptic procedure for which the challenge-response method

isused. According to the procedure, the Authentication Center (AUC) of the Mobile Switching Center (MSC) generates the 128-bit long random number using a random number generator

. Thegenerated RAND is then transmitted to the mobile station

, anda 32-bit long value is calculated from the RAND number using the secret key and the A3 algorithm, both of which are stored on the SIM card

and arealso known to the Authentication Center. The value calculated by the mobile station is transmitted to the AUC as an encrypted response

(SRES) and compared with the value calculated there. If the values match, the subscriber

isauthorized to access

the network.

The advantage of this procedure is that no personal data and keys are transmitted for the network access authorization check.

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Englisch: random number - RAND
Updated at: 21.11.2018
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