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4G/LTE - NAS |
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EEA(EPS Encryption Algorithms)
Simply put, this is a Ciphering Algorithm. and Ciphering can be aplied to both U-Plane Data and C-Plane Data (RRC/NAS Message). The type of EEA being used is determined by Network and informed to UE via Security Mode Command. NAS EEA is carried by NAS:Security Mode Command and RRC EEA is carried by RRC:Security Mode Command.
NAS_LTE:EMM,Security mode command Security mode command ::= DIVISION +-Security header type ::= V | +-Security header type ::= CHOICE [Plain NAS message, not security protected] +-EPS mobility management protocol discriminator ::= V | +-Protocol discriminator ::= PD [7] +-Security mode command message identity ::= V | +-Message type ::= MSG [5D] +-Selected NAS security algorithms ::= V | +-Octet1 ::= DIVISION | +-spare ::= FIX [0] | +-Type of ciphering algorithm ::= CHOICE [EPS encryption algorithm EEA0(ciphering not used)] | +-spare ::= FIX [0] | +-Type of integrity protection algorithm ::= CHOICE [Reserved 0] +-Spare half octet ::= V | +-Spare half octet ::= FIX [0] +-NAS key set identifier ::= V | +-TSC ::= CHOICE [native security context (for KSI ASME)] | +-NAS key set identifier ::= CHOICE [possible values for the NAS key set identifier 0] +-Replayed UE security capabilities ::= LV | +-Octet1 ::= DIVISION | | +-Length of UE security capability contents ::= LEN (0..255) [5]
+-c1 ::= CHOICE [securityModeCommand] +-securityModeCommand ::= SEQUENCE +-rrc-TransactionIdentifier ::= INTEGER (0..3) [0] +-criticalExtensions ::= CHOICE [c1] +-c1 ::= CHOICE [securityModeCommand-r8] +-securityModeCommand-r8 ::= SEQUENCE [0] +-securityConfigSMC ::= SEQUENCE | +-securityAlgorithmConfig ::= SEQUENCE | +-cipheringAlgorithm ::= ENUMERATED [eea0] | +-integrityProtAlgorithm ::= ENUMERATED [spare1] +-nonCriticalExtension ::= SEQUENCE OPTIONAL:Omit
Currently there are three different types of EEA we can use as shown in the following table.
Reference :
[1] The New LTE Cryptographic Algorithms EEA3 and EIA3
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