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<TD borderColor=#6699ff><FONT
size=2>您的位置：技术园地>技术讲座-GSM蜂窝移动通信系统 </FONT></TD></TR>
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<DIV align=center><FONT size=4><B><SPAN
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lang=EN-US>第三讲 GSM关键技术</SPAN></SPAN></B></FONT></DIV></TD></TR>
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style="FONT-FAMILY: 宋体; mso-hansi-font-family: 'Times New Roman'">3.11<SPAN
style="mso-spacerun: yes"> </SPAN>保密措施<O:P>
</O:P></SPAN></B></P>
<P class=MsoNormal
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</SPAN><FONT face=楷体_GB2312
color=#000066>大家都知道，GSM系统在安全性方面有了显著的改进，其主要是在下列部分<BR>加强了保护：接入网路方面采用了对客户鉴权；无线路径上采用对通信信息<BR>加密；对移动设备采用设备识别；对客户识别码用临时识别码保护；SMI卡用PIN码保护。</FONT></FONT></SPAN></P>
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size=3><O:P></O:P></FONT></SPAN></P>
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</SPAN><FONT color=#0000cc>(1)提供三参数组<O:P>
</O:P></FONT><O:P></O:P></FONT></SPAN></P>
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color=#000066>客户的鉴权与加密是通过系统提供的客户三参数组来完成的。客户三参数组的产生是在GSM系统的AUC(鉴权中心)中完成，如图3-39所示。每个客户在签约(注册登记)时，就被分配一个客户号码(客户电话号码)和客户识别码(IMSI)。IMSI通过SIM写卡机写入客户SIM卡中，同时在写卡机中又产生一个对应此IMSI的唯一的客户鉴权键Ki，它被分别存储在客户SIM卡和AUC中。AUC中还有个伪随机码发生器，用于产生一个不可预测的伪随机数(RAND)。RAND和Ki经AUC中的A8算法(也叫加密算法)产生一个Kc(密钥)，经A3算法(鉴权算法)产生一个响应数(SRES)。由产生Kc和SRES的RAND与Kc、SRES一起组成该客户的一个三参数组，传送给HLR，存储在该客户的客户资料库中。一般情况下，AUC一次产生5组三参数，传送给HLR，HLR自动存储。HLR可存储10组三参数，当MSC／VLR向HLR请求传送三参数组时，HLR<O:P></O:P></FONT></FONT></SPAN><FONT
face=楷体_GB2312 color=#000066><FONT size=3>又一次性地向<SPAN
lang=EN-US>MSC／VLR传5组三参数组。MSC／VLR一组一组地用，用到剩2组时，再向HLR请求传送三参数组。<O:P>
</O:P></SPAN></FONT></SPAN></FONT><FONT face=楷体_GB2312><SPAN
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size=3><SPAN lang=EN-US><O:P></O:P></SPAN></FONT></SPAN></FONT><FONT
face=楷体_GB2312><SPAN
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<IMG height=210 src="g3-11.files/g3-11.5.gif" width=297
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align=center><SPAN
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face=楷体_GB2312 color=#000066 size=3>图<SPAN lang=EN-US>3-39
三参数组的提供<O:P> </O:P></SPAN></FONT><FONT face=楷体_GB2312 size=3><SPAN
lang=EN-US><O:P></O:P></SPAN></FONT><FONT face=楷体_GB2312
size=3><SPAN lang=EN-US><O:P></O:P></SPAN></FONT><FONT size=3><SPAN
lang=EN-US><O:P></O:P></SPAN></FONT></SPAN></P>
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align=center><SPAN
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size=3><SPAN lang=EN-US><O:P></O:P></SPAN></FONT></SPAN></P>
<P class=MsoNormal
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style="FONT-FAMILY: 宋体; mso-hansi-font-family: 'Times New Roman'"><SPAN
style="mso-spacerun: yes"><FONT size=3> </FONT></SPAN><FONT
size=3><O:P> </O:P></FONT></SPAN></P>
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size=3><SPAN style="mso-spacerun: yes"> </SPAN><FONT
color=#0000cc>(2) 鉴权<O:P> </O:P></FONT><O:P></O:P></FONT></SPAN></P>
<P class=MsoNormal
style="MARGIN-TOP: 0px; TEXT-JUSTIFY: inter-ideograph; MARGIN-BOTTOM: 0px; TEXT-ALIGN: justify"><FONT
size=3><SPAN lang=EN-US
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color=#000066>鉴权的作用是保护网路，防止非法盗用。同时通过拒绝假冒合法客户的</FONT></SPAN><FONT
face=楷体_GB2312 color=#000066><SPAN lang=EN-US
style="mso-ascii-font-family: 宋体">“</SPAN> 入侵</SPAN><SPAN lang=EN-US
style="mso-ascii-font-family: 宋体">”</SPAN> 而保护<SPAN
lang=EN-US>GSM移动网路的客户。鉴权的程序见图3-40，当移动客户开机请求接入网路时，MSC／VLR通过控制信道将三参数组的一个参数伪随机数RAND传送给客户，SIM卡收到RAND后，用此RAND与SIM卡存储的客户鉴权键Ki，经同样的A3算法得出一个响应数SRES，传送给MSC／VLR。MSC／VLR将<O:P>
</O:P></SPAN></FONT><SPAN
style="FONT-FAMILY: 宋体; mso-hansi-font-family: 'Times New Roman'"><SPAN
lang=EN-US><O:P></O:P></SPAN></SPAN></FONT><SPAN
style="FONT-FAMILY: 宋体; mso-hansi-font-family: 'Times New Roman'"><FONT
face=楷体_GB2312 color=#000066 size=3>收到的<SPAN
lang=EN-US>SRES与三参数组中的SRES进行比较。由于是同一RAND，同样的Ki和A3算法，因此结果SRES应相同。MSC／VLR比较的结果相同就允许接入，否则为非法客户，网路拒绝为此客户服务。<O:P>
</O:P></SPAN></FONT></SPAN></P>
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face=楷体_GB2312 color=#000066><SPAN
style="FONT-FAMILY: 宋体; mso-hansi-font-family: 'Times New Roman'"><FONT
size=3>在每次登记、呼叫建立尝试、位置更新以及在补充业务的激活、去活、登记或删除之前均需要鉴权。<SPAN
lang=EN-US><O:P> </O:P></SPAN></FONT></SPAN></FONT></P>
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