3GPP TSG SA WG3 (Security)	3GPP S3-99312
Sophia Antipolis, 29 September-1 October, 1999	

Agenda Item:	9.2

Source:	Nokia

Title:	Draft CR to 33.102 on integrity procedures

Document for:	decision

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Reason for change
This draft CR introduces in 33.102, the signaling procedure use to set up ciphering and integrity check. Such an signaling is needed by other 3GPP groups to design appriate protocols. Furthermore,  in a second signaling diagram, this CR proposes a method to recover from  a failure of transmission due to e.g. repeated integrity check failure , new RNC not supporting negotiated ciphering algorithm, one of COUNT parameters becomes out of synchronisation, periodic authentication failure… We considered first to drop the RRC connection, but this would allow an invalid UE to drop the connection of a valid user. Therefore, our conclusion is that a full authentication procedure is needed to recover from such situation. We propose here that RNC may request this authentication from CN through a request security check message.
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6.X Signaling flow to start ciphering and integrity checking
The figure below illustrate the signaling procedure.

Before the procedure is initiated, the UE is in not having an RRC connection.
1.	The UE establishes an RRC connection [3GPP TS 25.331]. During this procedure the COUNT parameter (or its most significant part, i.e. the hyperframe number) is transferred from UE to RNC [missing in v1.3.0]
2.	The UE sends an initial L3 message. This message could be a Service Request, Routing area update request, attach request, paging response. This message is neither ciphered nor integrity checked. This message shall include KSI stored in UE. SGSN/VLR needs to perform security procedure. If KSI corresponds to a valid authentication vector stored in SGSN/VLR it may not perform an authentication. Otherwise SGSN/VLR shall perform an authentication procedure.
Note: This initial L3 message may contain the MS network capability.

3.	The SGSN sends an  user authentication request (RAND; AUTN ;  KSI). After the authentication procedure, the new CK and IK are stored in the UE together with KSI. 
4.	The UE sends an user authentication response (RES).
5	 SGSN/VLR sends Security mode command (CK, IK, UEA(s), UIA(s); KSI). UEA(s) and UIA(s) indicate the list of algorithm(s) that RNC may use. RNC selects the first UEA and the first UIA it supports in the list.
6	RNC stores the keys, generate FRESH and RNC sends Security control command to the UE (UIA; UEA; FRESH; KSI). RNC may choose the algoritm(s) from the set received from SGSN/VLR. This message shall be integrity checked. RNC is now prepared to receive ciphered and integrity checked uplink message.
Note: The use of uplink Activation Time mentioned in [3GPP TS 25.331 v1.3.0] is unclear.
7	UE starts ciphering and integrity checking for uplink and downlink. It sends Security control response to RNC using ciphering and integrity checking.
8	RNC starts ciphering and integrity checking for downlink . RNC sends Security mode complete to SGSN (UIA; UEA). UIA and UEA indicates the security algorithm used.
After this procedure, ciphered and integrity checked channels are established.

6.Y Signaling procedure in case of radio transmission failure due to ciphering or integrity problem.

This procedure is used by the RNC to request the 3G-SGSN/VLR to perform an authentication and to provide a new CK and IK.

RNC detects that new security parameters are needed. This may be triggered by (repeated) failure of integrity checks (e.g. COUNT went out of synchronisation), failure of periodic authentication, the new RNC does not support an algorithm selected by the old RNC.
1. RNC send a security check request to SGSN/VLR (indicating cause of the request). 
2. The SGSN/VLR performs the user authentication procedure. 
3. If the authentication is successful, the SGSN/VLR sends a Security mode command to RNC. This will restart the ciphering and integrity check with fresh parameter. If the authentication is not successful, the SGSN/VLR sends a Security check response (Cause) to RNC.