Ciphering(GBSS14.0_03)

GSM BSSGBSS14.0

Ciphering Feature ParameterDescription

Issue 03Date 2013-04-12

HUAWEI TECHNOLOGIES CO., LTD.

Copyright Huawei Technologies Co., Ltd. 2013. All rights reserved.No part of this document may be reproduced or transmitted in any form or by any means without prior writtenconsent of Huawei Technologies Co., Ltd. Trademarks and Permissions

and other Huawei trademarks are trademarks of Huawei Technologies Co., Ltd.All other trademarks and trade names mentioned in this document are the property of their respective holders. NoticeThe purchased products, services and features are stipulated by the contract made between Huawei and thecustomer. All or part of the products, services and features described in this document may not be within thepurchase scope or the usage scope. Unless otherwise specified in the contract, all statements, information,and recommendations in this document are provided "AS IS" without warranties, guarantees or representationsof any kind, either express or implied.

The information in this document is subject to change without notice. Every effort has been made in thepreparation of this document to ensure accuracy of the contents, but all statements, information, andrecommendations in this document do not constitute a warranty of any kind, express or implied. Huawei Technologies Co., Ltd.Address: Huawei Industrial Base

Bantian, LonggangShenzhen 518129People's Republic of China

Website: http://www.huawei.comEmail: [email protected]

Issue 03 (2013-04-12) Huawei Proprietary and ConfidentialCopyright Huawei Technologies Co., Ltd.

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Contents

1 About This Document..................................................................................................................11.1 Scope..................................................................................................................................................................11.2 Intended Audience..............................................................................................................................................11.3 Change History...................................................................................................................................................1

2 Overview.........................................................................................................................................43 Kc and Its Generation...................................................................................................................64 A5 Ciphering Algorithm..............................................................................................................75 Algorithm Selection......................................................................................................................96 Signaling Procedure....................................................................................................................117 Improvements in A5 Ciphering Algorithm............................................................................138 Impact on KPI...............................................................................................................................159 Engineering Guidelines.............................................................................................................1710 Parameters...................................................................................................................................1811 Counters......................................................................................................................................2912 Glossary.......................................................................................................................................3013 Reference Documents...............................................................................................................31

GSM BSSCiphering Feature Parameter Description Contents


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1 About This Document1.1 Scope

This document describes ciphering of Huawei GBSS. It covers the function of and technologymechanisms regarding this feature, including the ciphering key (Kc) generation, A5 cipheringalgorithm, ciphering algorithm selection, signaling procedure, and improvements in A5ciphering algorithm.

1.2 Intended AudienceIt is assumed that users of this document are familiar with GSM basics and have a workingknowledge of GSM telecommunication.This document is intended for:l Personnel working on Huawei GSM products or systemsl System operators who need a general understanding of this feature

1.3 Change HistoryThe change history provides information on the changes in the ciphering feature in differentdocument versions.There are two types of changes, which are defined as follows:l Feature change

Feature change refers to the change in the ciphering feature of a specific product version.l Editorial change

Editorial change refers to the change in wording or the addition of the information that wasnot described in the earlier version.

Document IssuesThe document issues are as follows:

GSM BSSCiphering Feature Parameter Description 1 About This Document


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l 03 (2013-04-12)l 02 (2012-12-31)l 01 (2012-04-28)l Draft A (2012-02-15)

03 (2013-04-12)This is the third commercial release of GBSS14.0.Compared with issue 02 (2012-12-31), 03 (2013-04-12) incorporates the changes described inthe following table.

Change Type Change Description Parameter ChangeFeature change None NoneEditorial change Optimized chapter "8 Impact on KPI." None

02 (2012-12-31)This is the second commercial release of GBSS14.0.Compared with issue 01 (2012-04-28), 02 (2012-12-31) incorporates the changes described inthe following table.

Change Type Change Description Parameter ChangeFeature change Added the description of randomization

of filling information of SI 6 in chapter"7 Improvements in A5 CipheringAlgorithm."

Added the followingparameter:SI6RandomBit

Editorial change None None

01 (2012-04-28)This is the first commercial release of GBSS14.0.Compared with issue Draft A (2012-02-15), issue 01 (2012-04-28) incorporates the changesdescribed in the following table.



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Change Type Change Description Parameter ChangeFeature change Added the description of

the encryption algorithmpriority. For details, see "5Algorithm Selection".

Added the following parameters:l EncryptionAlgorithm1stl EncryptionAlgorithm2ndl EncryptionAlgorithm3rdl EncryptionAlgorithm4thl EncryptionAlgorithm5thl EncryptionAlgorithm6thl EncryptionAlgorithm7th

Editorial change None None

Draft A (2012-02-15)This is the draft A release of GBSS14.0.Compared with issue 01 (2011-03-31) of GBSS13.0, issue Draft A (2012-02-15) of GBSS14.0has no change.



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2 OverviewThe information ciphered on the Um interface involves signaling, speech, and data. Theimplementation of ciphering guarantees the information security and prevents user informationor conversation contents from unauthorized access.The ciphering procedure is initiated on the network side. The BTS and MS cipher and decipherthe information by using the A5 algorithm and the ciphering key (Kc) generated by the A8algorithm on the basis of the capability of the MS and BTS. Thus, the security of the informationon the Um interface is ensured. The Kc is generated by the GSM authentication center (AuC)and stored in the MSC/VLR. The Kc is sent to the BTS before the ciphering procedure begins.The MS and the network adopt the A8 algorithm to generate the Kc by using the same Ki andrandom number (RAND).A ciphering or deciphering sequence is generated through the A5 algorithm on the basis of theKc stored in the MS and the network and the frame number from the current pulse stream. Thenetwork uses the same ciphering sequence in the uplink and downlink. For each burst, the datais ciphered or deciphered as follows:l One sequence is used for the MS ciphering and BTS deciphering.l The other sequence is used for the BTS ciphering and MS deciphering.The GSM specifications define the following ciphering algorithms:l A5/0 Ciphering Algorithml A5/1 Ciphering Algorithml A5/2 Ciphering Algorithml A5/3 Ciphering Algorithml A5/4 Ciphering Algorithml A5/5 Ciphering Algorithml A5/6 Ciphering Algorithml A5/7 Ciphering Algorithm

NOTEA5/0 means no ciphering at all.

Huawei GBSS supports A5/1, A5/2, and A5/3 ciphering algorithms.A network operator can use the A5 ciphering algorithm only after being granted by the 3GPPOrganizational Partners. As A5/1 and A5/2 ciphering algorithms have been decoded, it is

GSM BSSCiphering Feature Parameter Description 2 Overview


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advisable that you use the more secure A5/3 ciphering algorithm or the A5/1 ciphering algorithmwith A5/1 Encryption Flow Optimization enabled.The ciphering algorithms are selected on the basis of the capabilities of the network and MS.The ciphering algorithms to be adopted should be those allowed in the ciphering commanddelivered by the MSC, allowed in the BSC data configuration, and supported by the MS. TheBSC selects the appropriate ciphering algorithms based on the priorities of the algorithms. If theBSS does not support the ciphering algorithms allowed in the ciphering command delivered bythe MSC, the ciphering is rejected.The A5 ciphering algorithm provides weak protection for data security. Therefore, the cipheringprocedure is optimized on the basis of the characteristics of the Um interface transmission inGSM, thus enhancing transmission security and network bugging defense.

GSM BSSCiphering Feature Parameter Description 2 Overview


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3 Kc and Its GenerationThis describes the application and generation of the ciphering key (Kc).The MS and the network use the same Kc for ciphering and deciphering user data.An MS is allocated an International Mobile Station Identity (IMSI) and Ki after it is registeredin the GSM network. The MS and the network use the same Ki and RAND. The RAND isgenerated by the network and sent to the MS. Both the network and the MS use the A8 algorithmto generate the ciphering key Kc. Figure 3-1 shows the generation of the Kc.

Figure 3-1 Generation of Kc

GSM BSSCiphering Feature Parameter Description 3 Kc and Its Generation


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4 A5 Ciphering AlgorithmThis describes the application of the A5 ciphering algorithm, which is used to generate a pseudo-random sequence. (GBFD-113501 A5/1 and A5/2 Ciphering Algorithm, GBFD-113503 A5/3Ciphering Algorithm)The A5 ciphering algorithm generates a 114-bit ciphering sequence or a 114-bit decipheringsequence based on the 64-bit Kc stored in the MS and the network, and a 22-bit frame numberfrom the current pulse stream. The data ciphering/deciphering is achieved through the ExclusiveOR operation between the ciphering/deciphering sequence and the information bit in theciphered/deciphered data according to the A5 algorithm.The network uses the same ciphering sequence in the uplink and downlink. For each burst, onesequence is used for the MS ciphering and BTS deciphering whereas the other is used for theBTS ciphering and MS deciphering.The ciphering/deciphering on the radio links is performed by the BTS and MS. Figure 4-1 showsthe ciphering/deciphering process.

Figure 4-1 Ciphering/deciphering process

GSM BSSCiphering Feature Parameter Description 4 A5 Ciphering Algorithm


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GSM BSSCiphering Feature Parameter Description 4 A5 Ciphering Algorithm


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5 Algorithm SelectionThe ciphering algorithms are selected on the basis of the capabilities of the network, BSS, andMS. The ciphering algorithm supported by the BSS side is specified by the parameterENCRY.The process of selecting the ciphering algorithms is as follows:1. In the call access procedure, the MS sends an Establish Indication message to the BSC.

l If the parameter ECSC in the system information is set to No, the MS reports Classmark1 or Classmark 2, indicating whether the MS supports A5/1, A5/2, and A5/3 cipheringalgorithms.

l If the parameter ECSC in the system information is set to Yes, the MS reports Classmark1, Classmark 2, and Classmark 3, indicating whether the MS supports A5/1, A5/2, A5/3,A5/4, A5/5, A5/6, and A5/7 ciphering algorithms.

2. On receiving the Cipher Mode Command message from the MSC, the BSC checks theclassmarks reported by the MS. If the BSC does not receive Classmark 3, the BSC sendsa Classmark Enquiry message to the MS, asking the MS to report Classmark 3. Classmark3 defines whether an MS supports A5/4, A5/5, A5/6, and A5/7 ciphering algorithms.

The selection of the ciphering algorithms follows the following principles:l The ciphering algorithms to be adopted should be those supported by the MSC, allowed in

the BSC data configuration, and supported by the MS.l Set the priorities of the ciphering algorithms by setting EncryptionAlgorithm1st,

EncryptionAlgorithm2nd, EncryptionAlgorithm3rd, EncryptionAlgorithm4th,EncryptionAlgorithm5th, EncryptionAlgorithm6th, and EncryptionAlgorithm7th. If youdo not perform any configurations on the priority, use the default priority.

l The BSC selects the appropriate ciphering algorithms based on the priorities of thealgorithms, and then sends an Encryption Command message to the BTS.

NOTE

The default priorities of the ciphering algorithms are decreased from A5/7 to A5/0.

GSM BSSCiphering Feature Parameter Description 5 Algorithm Selection


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CAUTIONl If the BSS does not support the ciphering algorithms specified in the Cipher Mode Command

message, it sends the MSC a Ciphering Mode Reject message with the cause value CipheringAlgorithms Not Supported.

l If the MSC requests to change the ciphering algorithms while the BSS has enabled the formerciphering algorithms, the BSS sends a Ciphering Mode Reject message to the MSC.

GSM BSSCiphering Feature Parameter Description 5 Algorithm Selection


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6 Signaling ProcedureThis describes the signaling procedure for ciphering. The ciphering procedure generally appliesto location update, service access, and inter-BSC handover. It requests that the BSC and MSCare configured with the ciphering algorithms and that the BTS and MS have the codec capabilitiesassociated with the ciphering algorithms.The application of ciphering algorithms in the radio telecommunications system depends on theradio resources management entity. Figure 6-1 shows the ciphering procedure, which is initiatedby the network and executed by the BTS.

Figure 6-1 Ciphering procedure

Initiating the Setting of the Ciphering ModeWhen the authentication procedure is complete, the MSC sends the BSC a Ciphering ModeCommand message, which contains the Kc. The BSC sends a Ciphering Mode Commandmessage to the MS through the BTS. This message indicates whether the ciphering should beperformed by the MS and which ciphering algorithm should be used by the MS.

Completing the Setting of the Ciphering ModeCompleting the setting of the ciphering mode involves the following operations:

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1. On receiving a valid Ciphering Mode Command message, the MS loads the Kc stored inthe SIM card. If the MS receives an invalid Ciphering Mode Command message, themessage is considered erroneous. In this case, the MS sends an RR Status message withthe cause value Protocol Error and does no further processing.A valid Ciphering Mode Command message is defined to be one of the following:l One that indicates "start ciphering" and is received by the MS in "not ciphered" mode.l One that indicates "no ciphering" and is received by the MS in "not ciphered" mode.l One that indicates "no ciphering" and is received by the MS in "ciphered" mode.

2. After the MS receives the Ciphering Mode Command message and finishes the ciphering,it begins to send and receive messages in ciphered mode.l If the MS has started certain operations specified in the Ciphering Mode Command

message, it sends a Ciphering Mode Complete message to the network.l If the "cipher response" field in the Ciphering Mode Command message is specified

"IMEISV request", the MS shall include its IMEI in the Ciphering Mode Completemessage.

3. On receiving the Ciphering Mode Complete message from the MS, the network startsinformation transmission in ciphered mode.

Rejecting the Ciphering ModeIf the BSS does not support the ciphering algorithms specified in the Cipher Mode Commandmessage, it sends the MSC a Cipher Mode Reject message with the cause value CipheringAlgorithm Not Supported.

GSM BSSCiphering Feature Parameter Description 6 Signaling Procedure


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7 Improvements in A5 Ciphering AlgorithmThis describes the improvements in A5 ciphering algorithm against security problems. Theciphering procedure is optimized on the basis of the characteristics of the Um interfacetransmission in GSM, and thereby enhances transmission security and network bugging defense.( GBFD-113521 A5/1 Encryption Flow Optimization)The optimization of the ciphering procedure is achieved from the following aspects:l Fast SDCCH handover is adopted in the MS access process, which increases the difficulty

for the intruder to trace the user call.Fast SDCCH handover indicates that the BTS initiates an intra-cell SDCCH handoverimmediately after sending the ciphering command to the MS. Thus, the subsequent cipheredsignaling can be transmitted and received on a new signaling channel.SDFASTHOSWITCH specifies whether this function is enabled. To avoid incompatibilitywith the MS, the handover command is sent after the ciphering complete message isreceived.

l The TCH timing handover is introduced to increase the difficulty for the intruder to tracea user.For speech calls, intra-cell handovers are performed at a specified time.TCHTIMEHOSWITCH specifies whether the TCH timing handover is enabled. IfTCHTIMEHOSWITCH is set to Yes, the handover timer is started and the length of thetimer is TCHTIMEHOPERIOD. When TCHTIMEHOPERIOD expires, an intra-cellforced handover is performed.

l The Hopping Sequence Number (HSN) in the Flex Training Sequence Code (TSC) andFlex Mobile Allocation Index Offset (MAIO) differentiates one TCH from another.Therefore, the characteristics of TCHs are different and an intruder cannot trace other TCHsaccording to the characteristics of a certain TCH.Whether to enable the Flex TSC function depends on the setting of FLEXTSCSWITCH.If FLEXTSCSWITCH is set to Yes, the channels join in frequency hopping and eachchannel is randomly assigned a TSC, ranging from 0 to 7.

l After the BTS sends the ciphering command, it stops sending System Information 5, 5bis,and 5ter over the SACCH on the SDCCH.STOPSI5SWITCH specifies whether to stop the sending of system information. IfSTOPSI5SWITCH is set to Yes, the BTS stops sending System Information 5, 5bis, and5ter over the SACCH on the SDCCH after sending the ciphering command. Instead, theBTS sends System Information 6 or L2 fill frames.

GSM BSSCiphering Feature Parameter Description 7 Improvements in A5 Ciphering Algorithm


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l The dummy bits are randomized.DUMMYBITRANDSWITCH specifies whether to randomize the dummy bits. IfDUMMYBITRANDSWITCH is set to Yes, the BTS randomizes all the 0x2b dummy bitsin the signaling and all the dummy bits in L2 fill frames. To avoid incompatibility with theMS, the BTS reserves the initial 0x2b dummy bits when randomizing signaling.

l Filling information of SI 6 is randomized.The randomization of filling information of SI 6 is specified by SI6RandomBit. If thisparameter is set to YES(Yes), the BTS fills a random bit in the idle spare bit following thevalid information in SI 6 sent to the MS. The idle spare bit is contained in the SI6 rest octetsIE. The bit stream of SI 6 on the channel that carries the ongoing call changes after theciphering procedure starts. Therefore, intruders cannot compare the bit streams anddecipher the A5/1 ciphering algorithm.

GSM BSSCiphering Feature Parameter Description 7 Improvements in A5 Ciphering Algorithm


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8 Impact on KPIImpact on System Capacity

None

Impact on System PerformanceThe use of ciphering algorithms increases the signaling exchange and access delay of a call. Ifthe BSS does not support the specified ciphering algorithm, call admissions or handovers mayfail, and the system performance (for example, assignment success rate and handover successrate) is lowered.Enabling A5/1 Encryption Flow Optimization has the following impacts on system performance:l Quick SDCCH handover

The success rate of intra-cell handovers increases. Consequently, the handover successrate on the entire network increases. The number of intra-cell handovers increases. Consequently, the number of call drops

and the call drop rate increase.l Timing TCH handover

The success rate of intra-cell handovers increases. Consequently, the handover successrate on the entire network increases. The number of intra-cell handovers increases. Consequently, the number of call drops

and the call drop rate increase. In addition, the increased number of TCH handoversresults in an MOS decrease.

l Flex TSCIt is recommended that Flex TSC be enabled in an asynchronous network. This is becauseenabling Flex TSC will impair link performance and therefore lead to call drop, crosstalk,and noise in a synchronous network where Soft-Synchronized Network or IBCA is enabled.

l Stopping sending system information 5, 5bis, and 5ter after encryptionIf frequencies in the BA 1 and BA2 lists have been manually modified, the received systeminformation 5, 5bis, and 5ter may be incomplete. This increases the handover success rateand SDCCH call drop rate.

l Dummy bit randomizationThe dummy bit randomization has a slight impact on KPIs. It can decrease the probabilityof intermodulation interference generated when the MS receives signals and therefore

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decreases the probability of downlink call drops due to sequence errors. However, suchcall drops account for a small proportion of call drops on the live network. Therefore, theKPIs will not be affected greatly.

GSM BSSCiphering Feature Parameter Description 8 Impact on KPI


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9 Engineering GuidelinesHuawei equipment supports the following ciphering algorithms: A5/1, A5/2, and A5/3.The ciphering algorithms A5/1, A5/2, and A5/3 coexist in the same system and can be flexiblydefined through data configuration to meet specific regional requirements. The 3GPPOrganizational Partners allow all countries to apply for A5/1 or A5/3 because A5/2 is prone tobe decrypted. The A5/3 ciphering algorithm is preferred over other ciphering algorithms in termsof security.

GSM BSSCiphering Feature Parameter Description 9 Engineering Guidelines


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10 ParametersTable 10-1 Parameter description

Parameter ID NE MMLCommand

Feature ID Feature Name Description

DUMMYBITRANDSWITCH

BSC6900 SETGCELLSOFT

GBFD-113521 A5/1 EncryptionFlowOptimization

Meaning:Whether a BTSrandomizes thedummy bits inall messagesexcept systeminformation thatare sent to MSson dedicatedchannels. If thisparameter is setto OFF, dummybits are filled by0x2B. If thisparameter is setto ON, dummybits are filled byrandom values.GUI ValueRange:OFF(Off), ON(On)Unit:NoneActual ValueRange:OFF, ONDefaultValue:OFF(Off)

GSM BSSCiphering Feature Parameter Description 10 Parameters


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ECSC BSC6900 SETGCELLCCBASIC

GBFD-111101GBFD-114302

SystemInformationSendingGSM/TD-SCDMAInteroperability

Meaning:Theearly classmarksending control(ECSC)parameterspecifieswhether the MSsin a cell use earlyclassmarksending. After asuccessfulimmediateassignment, theMS sendsadditionalclassmarkinformation tothe network asearly aspossible. Theadditionalclassmarkinformationmainly containsthe CM3(classmark 3)information.The CM3(classmark 3)informationcontains thefrequency bandsupportcapability of theMS (used for thefuture channelassignment),powerinformationabout eachfrequency bandsupported by theMS (used for thehandoverbetweendifferentfrequencybands), andencryption



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capability of theMS.GUI ValueRange:NO(No),YES(Yes)Unit:NoneActual ValueRange:NO, YESDefaultValue:YES(Yes)

ENCRY BSC6900 SETGCELLBASICPARA

GBFD-113501GBFD-113503

A5/1 and A5/2CipheringAlgorithmA5/3 CipheringAlgorithm

Meaning:Encryption algorithmsupported by theBSS sideGUI ValueRange:A5/0,A5/1, A5/2,A5/3, A5/4,A5/5, A5/6,A5/7Unit:NoneActual ValueRange:A5/0,A5/1, A5/2,A5/3, A5/4,A5/5, A5/6,A5/7DefaultValue:A5/0-1&A5/1-0&A5/2-0&A5/3-0&A5/4-0&A5/5-0&A5/6-0&A5/7-0



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EncryptionAlgorithm1st

BSC6900 SETGCELLBASICPARA

GBFD-113501GBFD-113503GBFD-113521

A5/1 and A5/2CipheringAlgorithmA5/3 CipheringAlgorithmA5/1 EncryptionFlowOptimization

Meaning:Encryption algorithmwith priority 1.GUI ValueRange:A51(A5/1), A52(A5/2), A53(A5/3), A54(A5/4), A55(A5/5), A56(A5/6), A57(A5/7)Unit:NoneActual ValueRange:A51,A52, A53, A54,A55, A56, A57DefaultValue:A57(A5/7)

EncryptionAlgorithm2nd


GBFD-113501GBFD-113503GBFD-113521





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EncryptionAlgorithm3rd


GBFD-113501GBFD-113503GBFD-113521



EncryptionAlgorithm4th


GBFD-113501GBFD-113503GBFD-113521





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GBFD-113501GBFD-113503GBFD-113521





GBFD-113501GBFD-113503GBFD-113521





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GBFD-113501GBFD-113503GBFD-113521





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FLEXTSCSWITCH


GBFD-113521GBFD-118201GBFD-117001

A5/1 EncryptionFlowOptimizationSoft-SynchronizedNetworkFlex MAIO

Meaning:Whether to enable thefunction of theFlex trainingsequence code(TSC). If thevalue of thisparameter is ONand the BTSsupports theFlex TSCfunction, theBSSdynamicallyallocates TSCsto hoppingfrequencies forimproving thesecurity of calls.GUI ValueRange:OFF(Off), ON(On)Unit:NoneActual ValueRange:OFF, ONDefaultValue:OFF(Off)



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SDFASTHOSWITCH


GBFD-113503 A5/3 CipheringAlgorithm

Meaning:Whether to enable theSDCCH quickhandoverfunction. If thisparameter is setto ON, the BSChands over anMS to anotherSDCCH aftersending anencryptedcommand to theMS. Thisensures thatsubsequentencryptedcommands canbe sent andreceived on theSDCCH,increasingnetworksecurity.GUI ValueRange:OFF(Off), ON(On)Unit:NoneActual ValueRange:OFF, ONDefaultValue:OFF(Off)



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SI6RandomBit BSC6900 SETGCELLSOFT


Meaning:Whether to fill randombits in systeminformation (SI)6 after acipheringcommand issent.GUI ValueRange:NO(No),YES(Yes)Unit:NoneActual ValueRange:NO, YESDefaultValue:NO(No)

STOPSI5SWITCH



Meaning:Thisparameterspecifieswhether thesending ofsysteminformation 5,5bis, and 5tercan be stoppedon the SACCHon the SDCCHafter the BTSissues acipheringcommand.GUI ValueRange:OFF(Off), ON(On)Unit:NoneActual ValueRange:OFF, ONDefaultValue:OFF(Off)



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TCHTIMEHOPERIOD



Meaning:Thisparameterspecifies theinterval at whichthe speechservice on aTCH is handedover.GUI ValueRange:1~600Unit:sActual ValueRange:1~600Default Value:60

TCHTIMEHOSWITCH



Meaning:Thisparameterspecifieswhether toperformperiodic intra-cell handoverfor speechservices onTCH.GUI ValueRange:OFF(Off), ON(On)Unit:NoneActual ValueRange:OFF, ONDefaultValue:OFF(Off)



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11 CountersTable 11-1 Counter description

Counter ID Counter Name CounterDescription

NE Feature ID Feature Name

1282432419 CELL.SPT.CIPHER.CMD.A5.3

A3413C:Number of CipherCommands(A5/3)

BSC6900 GBFD-113503 A5/3 CipheringAlgorithm

1282432420 CELL.SPT.CIPHER.SUCC.A5.3

A3433S:Number of SuccessfulCipher Times(A5/3)

BSC6900 GBFD-113503 A5/3 CipheringAlgorithm

GSM BSSCiphering Feature Parameter Description 11 Counters


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12 GlossaryFor the acronyms, abbreviations, terms, and definitions, see the Glossary.

GSM BSSCiphering Feature Parameter Description 12 Glossary


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13 Reference Documents1. 3GPP 48.058: "Base Station Controller - Base Transceiver Station (BSC-BTS) Interface

Layer 3 Specification"2. BSC6900 Feature List3. BSC6900 Optional Feature Description4. BSC6900 GSM Parameter Reference5. BSC6900 GSM MML Command Reference6. BSC6900 GSM Performance Counter Reference

GSM BSSCiphering Feature Parameter Description 13 Reference Documents


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Contents1 About This Document1.1 Scope1.2 Intended Audience1.3 Change History

2 Overview3 Kc and Its Generation4 A5 Ciphering Algorithm5 Algorithm Selection6 Signaling Procedure7 Improvements in A5 Ciphering Algorithm8 Impact on KPI9 Engineering Guidelines10 Parameters11 Counters12 Glossary13 Reference Documents

Ciphering(GBSS14.0_03)

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