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.
|
Identifier |
Type |
Description |
|
0000 |
128-EEA0 |
Null ciphering algorithm |
|
0001 |
128-EEA1 |
SNOW 3G |
|
0010 |
128-EEA2 |
AES |
|
0011 |
128-EEA3 |
ZUC |
Reference :
[1] The New LTE Cryptographic Algorithms EEA3 and EIA3