3GPP TSG SA WG3 (Security) meeting #8	Tdoc S3-99456
Sophia Antipolis, 16-19 November 1999

			
	
3G CHANGE REQUEST	Please see embedded help file at the bottom of this
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	33.103	CR	001r1	Current Version:	3.0.0		
					
3G specification number 		 CR number as allocated by 3G support team	
	
For submision to TSG	SA#6	for approval	X	(only one box should	
list TSG meeting no. here 	for information		be marked with an X)	
	
Form: 3G CR cover sheet, version 1.0        The latest version of this form is available from: ftp://ftp.3gpp.org/Information/3GCRF-xx.rtf	
	
Proposed change affects:	USIM	X	ME		UTRAN		Core Network	X	
(at least one should be marked with an X)	
	
Source:	TSG SA WG3	Date: 	1999-11-18	
	
Subject:	Refinement of Enhanced User Identity Confidentiality	
	
3G Work item:	Enhanced User Identity Confidentiality	
	
Category: 	F	Correction					
	A	Corresponds to a correction in a 2G specification					
(only one category 	B	Addition of feature					
shall be marked	C	Functional modification of feature	X				
with an X)	D	Editorial modification					
	
Reason for 
change:
	This CR incorporates changes proposed to 33.102 related to refinement and clarification of enhanced user identity confidentiality mechanism.

Clauses affected:	3.3; 4.2.1; 6.2.1	
	
Other specs	Other 3G core specifications	X	  List of CRs:	33.102CR022r1	
affected:	Other 2G core specifications		  List of CRs:		
	MS test specifications		  List of CRs:		
	BSS test specifications		  List of CRs:		
	O&M specifications		  List of CRs:		
	
Other 
comments:		

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3.3	Abbreviations
For the purposes of the present document, the following abbreviations apply:
3GMS	Third Generation Mobile Communication System
AK	Anonymity Key
AUTN	Authentication Token
AUTS	Authentication Token for Synchronisation
AV	Authentication Vector
CK	Cipher Key
CS	Circuit Switched
DSK(X)(data)	Decryption of "data" with Secret Key of X used for signing EKSXY(i)(data)	Encryption of "data" with Symmetric Session Key #i for sending data from X to Y
EPK(X)(data)	Encryption of "data" with Public Key of X used for encryption
ECK	Network Wide Cipher Key
ECKC	Network Cipher Key Component for UE
ECKCpeer	Network Cipher Key Component for peer UE
EMSI	Encrypted Subscriber identity
GK	Group Key
GI	Group Identifier
Hash(data)	The result of applying a collision-resistant one-way hash-function to "data"
HE	Home Environment
HLR	Home Location Register
IK	Integrity Key
IMSI	International Mobile Subscriber Identity
IV	Initialisation Vector
KACX	Key Administration Centre of Network X
KSXY(i)	Symmetric Session Key #i for sending data from X to Y
KSI	Key Set Identifier
KSS	Key Stream Segment
LAI	Location Area Identity
MAP	Mobile Application Part
MAC	The message authentication code included in AUTN, computed using f1
MACS	The message authentication code included in AUTS, computed using f1*
MAC-I	Message authentication code for data integrity
MS	Mobile Station
MSC	Mobile Services Switching Centre
MT	Mobile Termination
NEX	Network Element of Network X
PS	Packet Switched
RAND	Random challenge
RANDms	Random value stored on MS received during user authentication request 
RNDX	Unpredictable Random Value generated by X
SEQ	Sequence number
SEQUIC	Sequence number
SN	Serving Network
TE	Terminal Equipment
Text1	Optional Data Field 
Text2	Optional Data Field
Text3	Public Key algorithm identifier and Public Key Version Number (eventually included in Public Key Certificate)
TMSI	Temporary Mobile Subscriber Identity
TTP	Trusted Third Party
UEA	UMTS Encryption Algorithm
UIA	UMTS Integrity Algorithm
UN	User Name
USIM	User Services Identity Module
VLR	Visited Location Register
X	Network Identifier
XMAC	Expected message authentication code for user authentication
XMAC-I 	Expected message authentication code for data integrity
XRES	Expected Response
XUR	Expected User Response
Y	Network Identifier
4.2	User services identity module
4.2.1	Enhanced User Identity Confidentiality (EUICUSIM)
For UMTS users with EUIC, the USIM has to store additional data and have additional functions implemented to encrypt the permanent user identity (IMSI). We describe the requirements as regards data storage and algorithm implementation for an example mechanism in annex B of 3G TS 33.102.
The following data elements need to be stored on the USIM:
a)	SQNUIC: a counter that is equal to the highest SQNUIC generated and sent by the USIM to the HE/HLR/AuC;
b)	GK: the group key used to encrypt the IMSI and SQNUIC;
c)	GI: a group identifier that identifies the group the user refers to as well as the GK;
d)	HLR-id consists of the first 3 digits of MSIN as a subaddress of HLR the user is related to;
Table 1: USIM – Enhanced User Identity Confidentiality – Data elements
Symbol	Description	Multiplicity	Lifetime	Length	Mandatory / Optional	
GK	Group key	1 per user group the user belongs to	Permanent	128 bits	Optional	
SQNUIC	Counter 	1 per user	Updated when protocol for EUIC is executed	32 bits	Optional	
GI	Group Identity	1 per user	Permanent	32 bits	Optional	
HLR-id	Subaddress of entitiy which can perform decryption
(first 3 digits of MSIN)	1 per user	Permanent	3 digits	Optional	

The following cryptographic functions need to be implemented in the HLR/AuC:
•	f6:	the user identity encryption function.
For a summary of the data elements and cryptographic function of the EUICHE function see Table 2.
Table 2: USIM– Enhanced User Identity Confidentiality – Cryptographic functions
Symbol	Description	Multiplicity	Lifetime	Standardised / Proprietary	Mandatory / Optional	
f6	User identity encryption function	1 	Permanent	Proprietary	Optional 	

4.6	Home location register / Authentication centre
4.6.1	Enhanced User Identity Confidentiality (EUICHE)
For UMTS users with EUIC, the HLR/AuC has to store additional data and have additional function implemented to decrypt the permanent user identity (IMSI). We describe the requirements as regards data storage and algorithm implementation for the example mechanism in annex B of 3G TS 33.102.
The following data elements need to be stored on the HLR/AuC:
a)	GK: the group key used to decrypt the IMSI and SQNUIC;
b)	GI: a group identifier that identifies the group the user refers to as well as the GK;
Table 18: HLR/AuC – Enhanced User Identity Confidentiality – Data elements
Symbol	Description	Multiplicity	Lifetime	Length	Mandatory / Optional	
GK	Group key	1 per user group 	Permanent	128	Optional	
GI	Group Identity	1 per user	Permanent	32 bits	Optional	

The following cryptographic functions need to be implemented in the HLR/AuC:
•	f7:	the user identity decryption function.
For a summary of the data elements and cryptographic function of the EUICHE function see Table 2.
Table19: HLR/AuC – Enhanced User Identity Confidentiality – Cryptographic functions
Symbol	Description	Multiplicity	Lifetime	Standardised / Proprietary	Mandatory / Optional	
f7	User identity decryption function	1 	Permanent	Proprietary	Optional