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LTE安全机制.pdf

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    Netmanias Technical Document: LTE Security II - NAS and AS Security www.nmcgroups.com LTE Security II - NAS and AS Security - October 14, 2014 (Initial Release: August 21, 2012) NMC Consulting Group (tech@netmanias.com) www.netmanias.com www.nmcgroups.com About NMC Consulting Group NMC Consulting Group is an advanced and professional network consulting company, specializing in IP network areas (e.g., FTTH, Metro Ethernet and IP/MPLS), service areas (e.g., IPTV, IMS and CDN), and wireless network areas (e.g., Mobile WiMAX, LTE and Wi-Fi) since 2002. Copyright © 2002-2014 NMC Consulting Group. All rights reserved.
    Netmanias Technical Document: LTE Security II - NAS and AS Security Protocol Stack for NAS and AS Security Setup Copyright © 2002-2014 NMC Consulting Group. All rights reserved. 2 xNAS Security SetupxxAS Security SetupxRRCNASRLCPDCPPHYRRCRLCPDCPPHYNASUEeNBMMELTE-UuMACMACApplicationIPRLCPDCPPHYRLCPDCPPHYUEeNBLTE-UuMACMACPerform ciphering/deciphering (encryption/decryption) and integrity protection/verificationKUPencKUPencKNASint User PlaneControl PlanePerform ciphering/deciphering (encryption/decryption) SRBIPDRBP-GWKNASencKNASint KNASencKRRCint KRRCencKRRCint KRRCencNAS Security Setup for signaling (NAS signaling)AS Security Setup for signaling (RRC signaling)and user IP packet
    Netmanias Technical Document: LTE Security II - NAS and AS Security Overview of LTE Security After Authentication  UE and MME share KASME After NAS Security Setup  UE and MME share NAS security keys (KNASenc, KNASint) in control plane After AS Security Setup  UE and eNB share AS security keys (KRRCenc, KRRCint) in control plane  UE and eNB share a AS security key (KUPenc) in user plane Copyright © 2002-2014 NMC Consulting Group. All rights reserved. 3 Attach Request (IMSI, UE Network Capability, KSIASME=7)Authentication Information Request (IMSI, SN ID, Network Type)Authentication Information Answer (AVs (1...n))Authentication Request (RAND, AUTNHSS, KSIASME=1) [not ciphered; not integrity protected]Authentication Response (RES) [not ciphered; not integrity protected]AS Security Mode Complete (MAC-I)[AS integrity protected]AS Security Mode Command(Ciphering Algorithm=EEA1, Integrity Algorithm=EIA1, MAC-I)[AS integrity protected]Attach Accept(UE Network Capability, KeNB)NAS Security Mode Command (KSIASME=1, Replayed UE Network Capability, NAS Ciphering Algorithm=EEA1, NAS Integrity Algorithm=EIA1, NAS-MAC)[NAS integrity protected]NAS Security Mode Complete (NAS-MAC) [NAS ciphered and integrity protected]Network(HSS) Authentication( AUTNUE = AUTNHSS )UE Authentication( RES = XRES )AuthenticationNAS Security SetupAS Security SetupCiphered and Integrity Protected NAS SignalingCompute KeNBCiphered and Integrity Protected RRC SignalingCiphered User Plane (Data Plane)KNASenc, KNASint KRRCenc, KRRCintKUPencKRRCenc, KRRCintKUPenceNBUEMMEHSS123LTE KRANDEPS AKA AlgorithmAUTNUERESKASMESQNSN IDLTE KRANDEPS AKA AlgorithmAUTNHSSXRESKASMESQNSN IDAuthentication Vector=(RAND, XRES, AUTNHSS, KASME)Select encryption/integrity algorithmKNASencKASMEKDFKNASintAlg-ID, Alg DistinguisherKNASenc, KNASint NAS Uplink CountKeNBKASMEKDFAlg-ID, Alg DistinguisherKRRCencKeNBKDFKRRCintKUPencSelect encryption/integrity algorithmNAS Uplink CountKeNBKASMEKDFKNASencKASMEKDFKNASintAlg-ID, Alg DistinguisherAlg-ID, Alg DistinguisherKRRCencKeNBKDFKRRCintKUPencLTE Security I - AuthenticationLTE Security II – NAS & AS Security
    Netmanias Technical Document: LTE Security II - NAS and AS Security [NAS Security Setup] Security Mode Command (1) Copyright © 2002-2014 NMC Consulting Group. All rights reserved. 4 [Prerequisite Process] ❶ ,❷ • • UE and MME share KASME after LTE authentication LTE authentication using EPS AKA procedure (refer to LTE Security I [1]) KASMEKNASencKNASintMMEAttach Request - IMSI- UE Network Capability . EEA0=on, EEA1=on, EEA2=off,… . EIA1=on, EIA2=on, … - KSIASME = 7Store UE Security CapabilityNAS Security Mode Command- KSIASME =1,- Replayed UE Security Capability,- NAS Ciphering Algorithm=EEA1,- NAS Integrity Algorithm=EIA1, - NAS-MACKDFKDFAlg-ID=01,NAS-int-alg=02EIANAS Security Mode Command MessageNAS-MACCOUNT,Bearer,DirectionIntegrity ProtectionSelect encryption/integrity algorithm (e.g., EEA1/EIA1)(from UE Security Capability)EIA1XNAS-MACIntegrity Verification (NAS-MAC = XNAS-MAC)KNASintKNASencCOUNT, Bearer,DirectionAlg-ID=01,NAS-enc-alg=01Alg-ID=01,NAS-int-alg=02KDFKDFKey Derivation1234Key DerivationAlg-ID=01,NAS-enc-alg=01KASME671UEMMEHSSKSIASMEAV1KASME iAuthenticationAuthentication Vectors KSIASMEAV1KASME i25KSIASME=1NAS Security Mode Command Message
    • KASME derived in ❷ (authentication process) • Security algorithm ID selected in ❶ • Security algorithm distinguisher KNASint = KDF (KASME, NAS-int-alg, Alg-ID) KNASenc = KDF (KASME, NAS-enc-alg, Alg-ID) Security Algorithm ID Algorithm Distinguisher Algorithm ID Description 128-EEA0 128-EEA1 128-EEA2 128-EEA3 128-EIA1 128-EIA2 128-EIA3 Null ciphering algorithm SNOW 3G AES ZUC (optional) SNOW 3G AES ZUC (optional) Value 0000 0001 0010 0011 0001 0010 0011 Algorithm Distinguisher NAS-enc-alg NAS-int-alg RRC-enc-alg RRC-int-alg UP-enc-alg UP-int-alg* Value 0x01 0x02 0x03 0x04 0x05 0x06 * for relay nodes only, not discussed herein Netmanias Technical Document: LTE Security II - NAS and AS Security [NAS Security Setup] Security Mode Command (2) ❶ [MME] Selection of security algorithms  Selects encryption and integrity protection algorithms applied to NAS messages based on UE Security Capability information (e.g. EEA1 and EIA1) ❷ [MME] Derivation of NAS security keys, KNASint and KNASenc  Derives KNASint and KNASenc with the following input parameters: ❸ [MME] Calculation of NAS-MAC for integrity protection  Generates Security Mode Command message and calculates NAS-MAC for the message using KNASint Calculation of NAS-MAC Copyright © 2002-2014 NMC Consulting Group. All rights reserved. Input Parameters for EIA Algorithm Input Parameter Description Count 32-bit downlink NAS count Message Direction Bearer KNASint NAS Message, Security Mode Command message herein 1-bit direction of message transmission, set to 1 for downlink 5-bit bearer ID, constant value (set to 0) 128-bit Integrity protection key for NAS messages 5 KASMEKNASencKNASintKDFKDFAlg-ID=01,NAS-int-alg=02Alg-ID=01,NAS-enc-alg=01EIANAS-MAC(KNASint)CountDirectionBearerKeyMessageSecurity Mode CommandMessage
    Netmanias Technical Document: LTE Security II - NAS and AS Security [NAS Security Setup] Security Mode Command (3) ❹ [UE  MME] Transmitting the Security Mode Command message  Security Mode Command: Integrity protected but not ciphered  MME sends the Security Mode Command (KSIASME, Replayed UE Security Capability, NAS Ciphering Algorithm, NAS Integrity Protection Algorithm) message with NAS-MAC to UE Information Element KSIASME Replayed UE Security Capability Description 3-bit value associated with a KASME, allocated by MME and used to identify the KASME, (KSIASME = 1 herein) UE Security Capability included in the Attach Request message sent by UE (parts of UE Network Capability) NAS Ciphering Algorithm NAS ciphering algorithm selected by MME, EEA1 herein NAS Integrity Protection Algorithm NAS integrity protection algorithm selected by MME, EIA1 herein ❺ [UE] Setting of KSIASME  Sets KSIASME to the same value of KSIASME in the Security Mode Command message (KSIASME : Identifier of KASME. Used on behalf of KASME between UE and MME) ❻ [UE] Derivation of NAS security keys, KNASint and KNASenc  Derives KNASint and KNASenc with the following the following input parameters: • KASME derived in ❷ (authentication process) • Security algorithm ID delivered in ❹ • Security algorithm distinguisher KNASint = KDF (KASME, NAS-int-alg, Alg-ID) KNASenc = KDF (KASME, NAS-enc-alg, Alg-ID) ❼ [UE] Integrity verification for the Security Mode Command message  Calculates XNAS-MAC, and performs integrity verification using KNASint by comparing NAS-MAC with the calculated XNAS-MAC Calculation of XNAS-MAC Copyright © 2002-2014 NMC Consulting Group. All rights reserved. 6 EIAXNAS-MACCountDirectionBearerMessageSecurity Mode CommandMessage(KNASint)Key
    Netmanias Technical Document: LTE Security II - NAS and AS Security [NAS Security Setup] Security Mode Complete (1) Copyright © 2002-2014 NMC Consulting Group. All rights reserved. 7 UEMMEGenerating NAS Security Mode Complete MessageEIA1NAS Security Mode Complete (NAS-MAC)EEA1Key Stream BlockPlain Text BlockCipher Text BlockCOUNT,Bearer,DirectionCOUNT, Bearer,Direction, LengthCipheringIntegrity ProtectionNAS-MACCiphered NAS Security Mode Complete MessageKNASintKNASencCOUNT,Bearer,DirectionXNAS-MACEEA1Key Stream BlockPlain Text BlockEIA1DecipheringKNASintKNASencNAS Security Mode Complete MessageCOUNT, Bearer,Direction, LengthCiphered NAS Security Mode Complete MessageIntegrity Verification (NAS-MAC = XNAS-MAC)89101211
    Netmanias Technical Document: LTE Security II - NAS and AS Security [NAS Security Setup] Security Mode Complete (2) ❽ [UE] Ciphering message using the selected ciphering algorithm  Generates Security Mode Complete message, then encrypts the message using KNASenc Ciphering of Security Mode Complete Message Input Parameters for EEA Algorithm Input Parameter Description Count 32-bit uplink NAS count Bearer 5-bit bearer ID, constant value (set to 0) Direction Length KNASenc 1-bit direction of message transmission, set to 0 for uplink length of key stream block 128-bit ciphering key for NAS messages ❾ [UE] Calculation of NAS-MAC for integrity protection  Calculates NAS-MAC for the ciphered Security Mode Complete message using KNASint Input Parameters for EIA Algorithm Input Parameter Description Count 32-bit uplink NAS count Message Direction Bearer KNASint NAS Message, Security Mode Complete message herein 1-bit direction of message transmission, set to 0 for uplink 5-bit bearer ID, constant value (set to 0) 128-bit integrity protection key for NAS messages Copyright © 2002-2014 NMC Consulting Group. All rights reserved. 8 EEAKey Stream BlockSecurity Mode Complete Message(KNASenc)CountBearerDirectionLengthKeyCiphered Security Mode Complete MessagePlain Text BlockCipher Text BlockEIANAS-MACCountDirectionBearerMessage(KNASint)KeyCiphered Security Mode Complete Message
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