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KDDI is a IS-95 CDMA carrier in Japan.

Background. KDDI is a IS-95 CDMA carrier in Japan. Many Japanese travel abroad, but few people come to Japan. (due to high consumer price in Japan?) Strong interest in ANSI-41 -> GSM roaming Less interest in GSM -> ANSI-41 roaming.

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KDDI is a IS-95 CDMA carrier in Japan.

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  1. Background • KDDI is a IS-95 CDMA carrier in Japan. • Many Japanese travel abroad, but few people come to Japan.(due to high consumer price in Japan?) Strong interest in ANSI-41 -> GSM roaming Less interest in GSM -> ANSI-41 roaming. • KDDI can rely on the IIF (Interworking Function) for roaming GSM to ANSI-41, which is planned to be deployed by some GSM carriers. • It is anticipated that only a few percent of KDDI users who subscribe GSM roaming, in other words who have SIM cards, will visit and stay in the GSM network. • Management of subscription data in IIF causes complexity.

  2. Main Concept • One-way roaming ANSI-41 to GSM. • No subscription data in IIF. • No impact on GSM infrastructure. • Few impacts on ANSI-41 infrastructure. • Concept allows CAVE based authentication by the ANSI-41 home while mobile is roaming in GSM system. • The length of authentication parameters of GSM MAP is longer than that of ANSI-41. Therefore, GSM MAP and air-interface can contain ANSI-41 authentication parameters. 2

  3. Mechanism This figure indicates the example of IIF interworking without Subscription data in IIF SIM Card *2 Security Related Information Request AUTHREQ *2 *2 authreq Authentication Vector Response GSMMSC/VLR (RAND, SRES, Kc) (RANDU, AUTHU) *1 ANSI-41 HLR IIF Mapping example RANDU (24bits) } AUTHU (18bits) } This SIM Card includes CAVE and A8 algorithm, and calculate AUTHU and SSD-B. AUTHU is contained in the SRES parameter. The SSD-B acts as Kc (ciphering key). And, this SIM Card contains MIN, ESN, fixed SSD-A and AAV parameter. 128bits 32bits RAND SRES AUTHU : AuthenticationResponseUniqueChallenge RANDU : RandVariableUniqueChallenge AAV : AuthenticationAlgorithmVersion *1 : HLR needs to contain fixed SSD-A for the roamer to GSM. *2 : This message is sent x times.

  4. Impact on ANSI-41 The IIF doesn’t know the ESN when the user initially made a registration in the GSM system. The IIF will set a default ESN in the initial REGNOT. The HLR has to accept the REGNOT. The HLR needs to contain a fixed SSD_A for each subscriber.

  5. Proposal - Authentication (without Subscription data) - ANSI-41MS GSM MSC/VLR IIF ANSI-41 HLR/AC ANSI-41 MSC/VLR no Subscription data ESN is set to a default value. Send_Auth_Req [IMSI, Number of requested vectors] AUTHREQ [MSID, ESN(fixed ESN), MSCID(IIF)] ANSI-41 HLR detects that MSCID parameter in AUTHREQ is IIF ID, it allows MSID/ESN mismatch, and it sends RANDU, AUTHU and SSD in authreq. It continues one to five times. authreq [RANDU, AUTHU, SSD] Send_Auth_Res [ AuthenticationSetList (RAND, SRES, Kc)] Authentication_Req (RAND) Authentication is needed. ANSI-41 MS executes the authentication using CAVE. It extracts RANDU from RAND in Auth_Req and calculates the AUTHU using RANDU and SSD-A. Authentication_Res (SRES) 4

  6. Initial Registration with Authentication (without Subscription data) [1/2] ANSI-41MS GSM MSC/VLR IIF ANSI-41 HLR/AC ANSI-41 MSC/VLR no Subscription data Update_Location_Req (IMSI) ESN is set to a default value. Send_Auth_Req [IMSI, Number of requested vectors] AUTHREQ [MSID, ESN(fixed ESN), MSCID(IIF)] ANSI-41 HLR detects that MSCID parameter in AUTHREQ is IIF ID, it allows MSID/ESN mismatch, and it sends RANDU, AUTHU and SSD in authreq. It continues one to five times. authreq [RANDU, AUTHU, SSD] Send_Auth_Res [ AuthenticationSetList (RAND, SRES, Kc)] Authentication_Req (RAND) ANSI-41 MS executes the authentication using CAVE. It extracts RANDU from RAND in Auth_Req and calculates the AUTHU using RANDU and SSD-A. Authentication_Res (SRES) 5

  7. Initial Registration with Authentication (without Subscription data) [2/2] ANSI-41MS GSM MSC/VLR IIF ANSI-41 HLR/AC ANSI-41 MSC/VLR Update_Location [IMSI] REGNOT [MSID, ESN(fixed ESN)] REGCANC [MSID, ESN] regcanc regnot [profile] Insert_Sub_Data Insert_Sub_Data ack Update_Location ack Update_Location_Ack 6

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