4.2.92 EFEPSNSC (EPS NAS Security Context)
31.1023GPPCharacteristics of the Universal Subscriber Identity Module (USIM) applicationRelease 17TS
If service n°85 is "available", this file shall be present.
This EF contains the EPS NAS Security context as defined in TS 33.401 [52]. This file shall contain only one record.
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Identifier: ‘6FE4’ |
Structure: linear fixed |
Optional |
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SFI: ’18’ |
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Record size: X bytes (X≥54) |
Update activity: high |
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Access Conditions: READ PIN UPDATE PIN DEACTIVATE ADM ACTIVATE ADM |
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Bytes |
Description |
M/O |
Length |
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1 to X |
EPS NAS Security Context TLV Object |
M |
X bytes |
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EPS NAS Security Context tags
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Description |
Tag Value |
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EPS NAS Security Context Tag |
‘A0’ |
EPS NAS Security Context information
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Description |
Value |
M/O |
Length (bytes) |
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EPS NAS Security Context Tag |
‘A0’ |
M |
1 |
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Length (length of all subsequent data) |
Y |
M |
Note 1 |
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Key set identifier KSIASME Tag |
’80’ |
M |
1 |
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Length |
K |
M |
Note 1 |
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Key set identifier KSIASME |
— |
M |
K |
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ASME key (KASME) Tag |
’81’ |
M |
1 |
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Length |
L |
M |
Note 1 |
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ASME key (KASME) |
— |
M |
L |
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Uplink NAS count Tag |
’82’ |
M |
1 |
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Length |
M |
M |
Note 1 |
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Uplink NAS count |
— |
M |
M |
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Downlink NAS count Tag |
’83’ |
M |
1 |
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Length |
N |
M |
Note 1 |
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Downlink NAS count |
— |
M |
N |
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Identifiers of selected NAS integrity and encryption algorithms Tag |
’84’ |
M |
1 |
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Length |
S |
M |
Note 1 |
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Identifiers of selected NAS integrity and encryption algorithms |
— |
M |
S |
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Note 1: The length is coded according to ISO/IEC 8825-1 [35] |
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– Key set identifier KSIASME Tag ’80’
Contents:
The ASME key set identifier as defined in TS 33.401 [52]. In this release the KSIASME is coded on 1 byte.
Coding:
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b8 |
b7 |
b6 |
b5 |
b4 |
b3 |
b2 |
b1 |
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KSIASME |
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bits b4 to b8 are coded 0 |
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– ASME key (KASME) Tag ’81’
Contents:
The ASME Key as defined in TS 33.401 [52]. In this release a valid ASME key is coded on 32 bytes. The ME shall treat any ASME key values stored in this EF as invalid if the ASME key set identifier indicates that no ASME key is available or if the length indicated in the ASME key TLV is set to ’00’,
Coding:
The most significant bit of KASME is the most significant bit of the 1st byte of this TLV value field. The least significant bit of KASME is the least significant bit of the last byte of this TLV value field.
– Uplink NAS count Tag ’82’
Contents:
The uplink NAS count as defined in TS 33.401 [52]. In this release the Uplink NAS count is coded on 4 bytes.
Coding:
The most significant bit of the uplink NAS count is the most significant bit of the 1st byte of this TLV value field. The least significant bit of the uplink NAS count is the least significant bit of the last byte of this TLV value field.
– Downlink NAS count Tag ’83’
Contents:
The downlink NAS count as defined in TS 33.401 [52]. In this release the downlink NAS count is coded on 4 bytes.
Coding:
The most significant bit of the downlink NAS count is the most significant bit of the 1st byte of this TLV value field. The least significant bit of the downlink NAS count is the least significant bit of the last byte of this TLV value field.
– Identifiers of selected NAS integrity and encryption algorithms Tag ’84’
Contents:
The identifiers of selected NAS integrity and encryption algorithms as defined in TS 33.401 [52] and TS 24.301 [51]. In this release the identifiers of selected NAS integrity and encryption algorithms are coded on 1 byte.
Coding:
as the content of the NAS security algorithms information element defined in TS 24.301 [51].
Byte 1 of this TLV value field: first byte of the NAS security algorithms information element
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b8 |
b7 |
b6 |
b5 |
b4 |
b3 |
b2 |
b1 |
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MSB |
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Unused bytes shall be set to ‘FF’.
In order to mark the stored EPS NAS security context as invalid:
– the record bytes shall be set to ‘FF’, or
– the KSIASME is set to ’07’, or
– the length indicated in the ASME key TLV is set to ’00’.