Reference Manual

Encryption
32 Encryption
Encryption is used for ciphering and deciphering of information to and
from an MS over a dedicated resource. The RBS supports two
encryption modes, either using no encryption or using a GSM
encryption algorithm.
The BSC controls which encryption mode is used.
There are two product variants with different encryption algorithms
implemented:
•
No encryption — GSM encryption algorithm version 1 (A5/1).
• No encryption — GSM encryption algorithm version 2 (A5/2).
32.1 References
/GSM 04.08/ GSM 04.08 (phase 2) version 4.7.0
/GSM 08.58/ GSM 08.58 (phase 2) version 4.7.0
Whenever a reference is made to a function described in another chapter,
please refer to the table of contents to find the appropriate chapter.
32.2 Start Encryption at Channel Activation
Purpose
To initiate encryption mode on a dedicated logical channel.
Precondition and initiation
The function starts encryption if element "Encryption Information" is
provided in the "CHANNEL_ACTIVATION" message.
Element "Encryption Information" is optional when the Channel
Activation types are:
• Normal Assign
• Asynchronous Handover
• Synchronous Handover
• Multislot Configuration
Element "Encryption Information" is not supported for Channel
Activation type "Immediate Assign".
Access burst, which is received from MS at handover access, is not
deciphered.
• Supported channel numbers: /GSM 05.02:6.4/
• Bm + ACCH
• Lm + ACCH
• SDCCH/8 + ACCH
• SDCCH/4 + ACCH (and TN=0)
EN/LZT 720 0008 P2A
2001-11-28
291 (485)
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