Content for TR 33.969 Word version: 17.1.0
4 Recommendations on security requirements of PWS
5 System architecture of PWS
6 Security features of PWS
7 Possible Security solutions of PWS
8 Evaluation of different solutions
9 Key issues for establishing service requirements and designing a PWS security system
10 Conclusion
A Archived solutions
B Threat discussion depending on the PWS settings in the UE relating to roaming
$ Change History
4 Recommendations on security requirements of PWS p. 12
5 System architecture of PWS p. 13
6 Security features of PWS p. 14
6.1 PWS threats and analysis p. 14
6.1.1 General p. 14
6.1.2 PWS Security circumvention attack p. 14
6.1.3 Spoofing, tampering, and suppressing p. 15
6.1.4 Threats to the delivery of the public key p. 15
6.1.5 Location of node protecting the public key delivery in PWS p. 16
6.2 Proposed security features of PWS p. 16
6.2.1 General p. 16
6.2.2 Restrictions on the PWS message signature length p. 18
6.2.2.1 General p. 18
6.2.2.2 Warning message format in CMAS, KPAS, and EU-Alert p. 18
6.2.2.3 Warning message format in ETWS p. 18
6.2.2.4 Conclusion on signature length p. 19
6.2.3 Algorithm agility of PWS p. 20
6.2.3.1 General p. 20
6.2.3.2 ECDSA domain parameters p. 20
6.2.4 Security level and key length of signature algorithms proposed p. 22
6.2.5 Verification of PWS Warning Notification message p. 24
6.2.6 Primary and secondary notifications p. 25
6.2.7 Network sharing impact to PWS Security p. 26
6.2.8 Triggering condition for public key update p. 28
6.2.9 Roaming impact to PWS Security p. 29
6.2.10 Discussion on parameters to be sent when distributing public keys or broadcasting warning messages p. 31
6.2.10.1 Public Key Identifier (PKID) p. 31
6.2.10.2 Signing entity identifier p. 31
6.2.10.3 Signature Algorithm Identifier (SAI) p. 32
6.2.10.4 Domain parameters p. 32
6.2.10.5 Domain set indicator p. 32
6.2.10.6 Hash function indicator p. 32
6.2.10.7 Network Security Use Counter (NSUC) p. 32
6.2.10.8 Void
6.2.10.9 Void
6.2.10.10 Conclusion p. 32
6.2.11 Considerations on networks in disaster areas p. 34
7 Possible Security solutions of PWS p. 34
7.0 General p. 34
7.1 Void
7.2 Void
7.3 Solution 3: NAS based solution p. 35
7.3.1 General p. 35
7.3.2 PWS public key distribution p. 35
7.3.2.1 Initial PWS public key distribution p. 35
7.3.2.2 Core network PWS public key configuration p. 37
7.3.2.3 PWS public key update p. 38
7.3.3 PWS Warning Notification message p. 40
7.3.4 Solutions to security issues in GSM/GPRS and with 2G subscribers in UMTS p. 43
7.3.4.1 General p. 43
7.3.4.2 Re-use current GSM/GPRS security mechanism with initiating ciphering p. 44
7.3.4.3 Enhanced integrity protection mechanism for GSM /GPRS p. 46
7.3.4.4 Limiting key updates in GSM/GPRS p. 47
7.3.4.5 Mechanisms of NAS solution for GSM/GPRS p. 47
7.3.4.6 Delaying public key update using a UE-controlled timer p. 47
7.4 Solution 4: GBA based protection p. 49
7.4.1 General p. 49
7.4.2 GBA based protection mechanism for public key distribution p. 49
7.4.2.1 Key establishment p. 49
7.4.2.2 Security protocol p. 51
7.4.3 Transport mechanisms p. 52
7.4.3.1 Transport mechanisms for establishment of GBA keys p. 52
7.4.3.2 Transport mechanisms for public key distribution p. 52
7.4.4 Analysis p. 54
7.4.4.1 Pros p. 54
7.4.4.2 Cons p. 54
7.4.4.3 Cost p. 54
7.4.4.4 Comparison to other solutions p. 55
7.5 Solution 5: using NAS layer security p. 56
7.5.1 High level solution discussion p. 56
7.5.2 Solution details p. 57
7.5.2.1 General p. 57
7.5.2.2 Changes in the mobility messages from the UE p. 57
7.5.2.3 Changes to the authentication procedure p. 57
7.5.2.4 Changes to context transfers between core network nodes p. 57
7.5.3 Comparison with other solutions p. 58
7.6 Solution 6: implicit certificate PKI based PWS solution p. 59
7.6.1 General p. 59
7.6.2 Certificate authorities p. 62
7.6.2.1 General p. 62
7.6.2.2 UE provisioning [public key] and [CA-ID] updating of home network p. 63
7.6.2.3 Roaming considerations p. 64
7.6.3 Implicit certificates p. 65
7.6.3.1 High level view of an implicit certificate approach from the UE perspective p. 65
7.6.3.2 Generation of implicit certificate p. 66
7.6.3.3 PWS Security contents p. 67
7.6.4 Properties of solution p. 70
7.7 Solution 7: generalized certificate-based approach for PWS p. 71
7.7.1 Introduction p. 71
7.7.2 Structure of CAs p. 72
7.7.2.1 Top-down approach to CAs p. 72
7.7.2.2 Bottom-up approach to CAs p. 72
7.7.2.3 More complex CA structures p. 72
7.7.2.4 Comparison with server certificates in other 3GPP specifications p. 73
7.7.3 Distribution of public root keys p. 74
7.7.3.1 Pre-installation in terminals at manufacturing time p. 74
7.7.3.2 Configuration when terminal is first taken into use p. 74
7.7.3.3 Public key update and revocation p. 74
7.7.3.4 Comparison with server certificates in other 3GPP specifications p. 74
7.7.4 Certificate format and distribution of certificates p. 75
7.7.5 Considerations on pre-provisioned CAs public keys shared by CBEs p. 76
7.8 Solution 8: national PWS solution based on UICC OTA p. 78
7.8.1 Introduction p. 78
7.8.2 Distribution of PWS public keys and parameters p. 79
7.8.3 Format and handling of PWS notification p. 80
7.9 Solutions to counter the PWS Security circumvention attack and to mitigate the risk of displaying false unprotected warning messages p. 81
7.9.0 General p. 81
7.9.1 Solution A: No display of unauthenticated warning messages p. 81
7.9.2 Solution B: Network-independent location verification p. 82
7.9.3 Solution C: Using a UE-controlled timer p. 84
7.9.4 Recommendation p. 84
7.10 The use of signing proxies p. 85
8 Evaluation of different solutions p. 88
8.1 Void
8.2 Void
8.3 Evaluation of solution 3 p. 88
8.3.1 Public key length p. 88
8.3.2 NAS message consumption for public key p. 88
8.3.3 Frequency of NAS message carrying public key p. 91
8.3.4 Number of CBEs / Signing proxy p. 92
8.3.5 Evaluation of solutions to security issues in GSM/GPRS and with 2G subscribers in UMTS p. 94
8.3.5.1 General p. 94
8.3.5.2 Re-use current GSM/GPRS security mechanism with initiating ciphering p. 94
8.3.5.3 Enhanced integrity protection mechanism for GSM /GPRS p. 94
8.3.5.4 Limiting key updates in GSM/GPRS p. 95
8.3.5.5 Mechanisms of NAS solution for GSM/GPRS p. 95
8.3.5.6 Delaying public key update using a UE-controlled timer p. 95
8.4 Void
8.5 Void
8.6 Evaluation of solution 6 and solution 7 p. 97
8.6.1 Same points for both p. 97
8.6.2 Specific points for implicit certificate based p. 97
8.6.3 Specific points for generalized certificate based p. 97
8.7 Void
8.8 Evaluation of solution 8 p. 98
8.9 Evaluation of signature algorithms in PWS p. 98
9 Key issues for establishing service requirements and designing a PWS security system p. 100
10 Conclusion p. 101
A Archived solutions p. 102
A.1 Solution 1 p. 102
A.1.1 Public key distribution p. 102
A.1.2 Public key distribution in UMTS p. 104
A.1.3 Signature algorithm agility p. 105
A.1.4 Distribution of signature algorithm identifier in UMTS p. 106
A.1.5 Verification of PWS Warning Notification message p. 107
A.2 Solution 2 p. 108
A.2.1 General p. 108
A.2.2 Initial PWS key distribution p. 108
A.2.3 Network PWS key configuration p. 109
A.2.4 PWS key update p. 109
A.2.5 Delivery of PWS Warning Notification message p. 111
B Threat discussion depending on the PWS settings in the UE relating to roaming p. 112
$ Change History p. 116
