2022 Advanced SIM
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Advanced SIM topics: ARA-M, SCP02, OTA, ISIM
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============================================
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:author: Harald Welte <laforge@gnumonks.org>
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:copyright: 2022 by Harald Welte (License: CC-BY-SA)
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:backend: slidy
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:max-width: 45em
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== Overview
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* Administrative Commands
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* ADF.ISIM
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* DF.5GS
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* ARA-M applet
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* GlobalPlatform SCP02
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* pySim-shell updates
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== Recap: Some smartcard terminology
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* card filesystem
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** *MF* (Master File): The root directory
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** *DF* (Dedicated File): A subdirectory
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** *ADF* (Application Dedicated File): Directory of an application (like USIM, ISIM)
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** *EF* (Entry File): A regulare file
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*** *Transparent EF*: An unstructured file
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*** *Linear Fixed EF*: An file consisting of fixed-length records
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== specs vs. proprietary
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* SIM cards are fully specified by a combination of ISU, ETSI and 3GPP specs
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* this covers only the operation after the card has been issued, e.g.
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** reading and writing files accessible without PIN auth, after PIN auth
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** performing GSM authentication or UMTS AKA
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* it does _not_ cover how the card is issued/provisioned
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** secret key material (Ki / K / OP / OPc) is not readable from the card
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** it is an implementation detail on how the card manufacturer writes those to the card
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* this leads to the need for card-specific support / code in software like pySim
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== Administrative Commands (TS 102 222)
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* most well-known SIM/UICC commands relate to normal operation
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** reflects what happens between phone (ME) and SIM
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** SELECT, {READ,UPDATE} {BINARY,RECORD}, VERIFY CHV, ...
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* there are also standardized _administrative_ commands
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** intended for use by the operator / card issuer
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** usually only work after authentication with ADM PIN or via secure channel
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== Administrative Commands (TS 102 222)
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* `CREATE FILE`
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* `DELETE FILE`
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* `DEACTIVATE FILE`
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** temporary deactivation (cannot be selected anymore)
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* `ACTIVATE FILE`
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** reactivation of deactivated files
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* `TERMINATE DF`
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** DF can never be used again
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* `TERMINATE EF`
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** EF can never be used again
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* `TERMINATE CARD USAGE`
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** permanently bricks the card
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== The ISIM application
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The history:
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* initial 2G SIM cards had `DF.GSM` + `DF.TELECOM`
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* ETSI UICC was specified as application-independent card
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* 3G/UMTS: 3GPP USIM application specified for UICC
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* 4G/LTE: continues to use USIM
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* IMS/VoLTE: optional ISIM application for UICC
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== ISIM application: Entirely optional
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* ISIM application is entirely optional
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* IMS (VoLTE, VoWiFi) can be used with pure USIM
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* without ISIM, default / fall-back mechanisms are used
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** P-CSCF address
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** Identities (IPUI derived from IMSI)
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== ISIM application: Files in USIM or ISIM
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Some files can either be in ADF.USIM **or** in ADF.ISIM
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* cards without ISIM might have them in USIM
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* cards with ISIM *must not* have them in USIM
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Files:
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* `EF.UICCIARI`
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* `EF.FromPreferred`
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* `EF.IMSConfigData`
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* `EF.XCAPConfigData`
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* `EF.MuDMiDConfigData`
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== ISIM application: Separate authentication context
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While IMS uses the same UMTS AKA Authentication Mechanism as 3G/4G systems,
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the authentication context can be different:
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* transport / access network (e.g. LTE) authenticates against USIM
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* IMS core network (e.g. P-CSCF) authenticates against ISIM
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At least in theory (and in practice with sysmoISIM-SJA2), one can configure
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different key material and even choose different algorithms for the two
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situations.
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== ISIM application: Files in ADF.ISIM
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image::adf_isim.png[align="center"]
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== ISIM application: Files in ADF.ISIM
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* `EV.IMPI` (IMS Private User Identity)
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* `EF.DOMAIN` (Home Network Domain Name)
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* `EF.IMPU` (IMS Public User Identity)
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* `EF.AD` (Administrative Data)
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* `EF.ARR` (Access Rule Reference)
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* `EF.IST` (ISIM Service Table, like EF.UST for USIM)
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* `EF.P-CSCF` (P-CSCF Address
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* `EF.GBABP` (GBA Bootstrapping Parameters)
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* `EF.NAFKCA` (NAF Key Centre Address)
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* `EF.SMS / EF.SMSS / EF.SMSR / EF.SMSP` (SMS like in GSM/USIM)
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* `EF.UICCIARI` (IMS Application Reference Identifier)
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* `EF.FromPreferred`
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* `EF.IMSConfigData`
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* `EF.XCAPConfigData`
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* `EF.WebRTCURI`
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* `EF.MuDMiDConfigData`
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== BER-TLV files (1/2)
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* new file type ('structure') from existing known types
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** transparent
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** linear fixed
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** cyclic
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* BER-TLV files store data in BER-TLV format [surprise!]
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* difference between storing BER-TLV in transparent file:
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** read/write/delete only TLV for a certain specific tag
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** no need to bother with padding
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* supported from sysmoISIM-SJA2v2 onwards (IMSI ending in >= 50000)
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== BER-TLV files (2/2)
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* USIM Files specified as BER-TLV:
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** `EF.URSP` (UE Route Selection Policies)
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** `DF.GRAPHICS/EF.ICE_graphics` (?)
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** `DF.MULTIMEDIA/EF.MML` (Multimedia Messages List)
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** `DF.MULTIMEDIA/EF.MMDF` (Multimedia Messages Data File)
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** `DF.MCS/EF.MCS_CONFIG` (Mission Critical Services)
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** `DF.V2X/EF.V2X_CONFIG` (V2X configuration Data)
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* ISIM Files specified as BER-TLV
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** `EF.IMSConfigData` (IMS Configuration Data)
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** `EF.MuDMiDConfigData` (Multi-Device / Multi-Identity Config)
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== 5G SIM / DF.5GS
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* 3GPP did not specify a new card application
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* 5G/NR uses the same USIM as 4G/LTE and 3G/UMTS
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* some optional additional files in ADF.USIM/DF.5GS
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** together with their associated _services_ (122-135)
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** `EF.5GS3GPPLOCI` (like EF.LOCI/3G and EF.EPSLOCI/4G)
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** `EF.5GSN3GPPLOCI` (non-3GPP location information)
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** `EF.5GS3GPPNSC` (NAS Security Context)
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** `EF.5GAUTHKEYS` (K_SEAF / K_AUSF, like EF.KEYS/3G)
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** `EF.UAC_AIC` (UAC Access Identities Configuration)
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** `EF.SUCI_Calc_Info` (For SUCI computation in ME)
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** `EF.OPL5G` (5GS Operator PLMN List)
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** `EF.SUPI_NAI` (SUPI as Network Access Identifier)
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** `EF.Routing_Indicator`
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** `EF.URSP` (UE Route Selection Policies per PLMN)
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** `EF.TN3GPPSNN` (Trusted non-3GPP Serving network names list)
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== 5G SIM / Files in DF.5GS
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image::df_5gs.png[align="center"]
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== 5G SIM / Calculation of SUCI on SIM
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* 5G introduces the optional SUCI security menchanism
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** SUCI == Subscriber Concealed Identifier
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* prevents IMSI (SUPI) transmission in plain-text
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* two implementation options:
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** SUCI computation on ME (phone) using key from SIM
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** SUCI computation on SIM card
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Some high-end cards (like eUICC) support SUCI calculation on the card.
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== ARA-M and Android Carrier Privileges
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* Android specific system to give apps more API access
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** change carrier/operator settings like APN, Roaming, ...
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** change IMS configuration for VoLTE / VoWiFi
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** inject SMS into android from an app
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* hash/cert of key used to sign app stored on SIM
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* if Android detects apps signed with matching key, API access is enabled
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* hash/cert is not stored as normal file in filesytem
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* requires _Secure Element Access Control_ application on card
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== ARA-M / Secure Element Access Control
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image::ara-m-architecture.png[width=1000,align="center"]
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== ARA-M in practice
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* minimal open source ARA-M applet: https://github.com/bertrandmartel/aram-applet
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* pre-installed on sysmoISIM-SJA2
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* pySim-shell has support for adding/deleting rules (see user manual)
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* see https://github.com/herlesupreeth/CoIMS_Wiki for more information
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== pySim-shell updates since April 2021
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* commands
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** more decoders for more files
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** TS 102 222 administrative commands
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** `ust_service_check`
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** `apdu` command
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** `export --json`
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* encoders/decoers
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** TLV definitions for IMS, XCAP and MudMid
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** FCP in `export`
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* BER-TLV file support
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* ARA-M support
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* support for generic, non-sysmocom cards
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* WIP
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** basic GlobalPlatform commands
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** `decode_hex` command
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== GlobalPlatform
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* GlobalPlatform specifies the Javacard universe
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* SIM cards are not required to be Java cards, but in practice they mostly are
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** ... and they mostly only implement ancient GlobalPlatform versions
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* specifies how to install/remove/lock/unlock applets
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* specifies transport layer security protocols (SCP02, SCP03)
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== GlobalPlatform APDU commands
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* Key Management
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** `PUT KEY`
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** `DELETE KEY`
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* Data
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** `GET DATA`
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** `STORE DATA`
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* Application Locking/Unlocking
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** `GET STATUS`
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** `SET STATUS`
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* Installation / Deletion (Executables, Applets)
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** `INSTALL`
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** `DELETE`
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== GlobalPlatform INSTALL / DELETE flavours
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* `INSTALL`
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** `INSTALL [for load]`
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** `INSTALL [for install]`
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** `INSTALL [for load, install and make selectable]`
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** `INSTALL [for install and make selectable]`
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** `INSTALL [for make selectable]`
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** `INSTALL [for extradition]`
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** `INSTALL [for registry update]`
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** `INSTALL [for personalization]`
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* `DELETE`
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** Executable Load File
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** Executable Load File and related Applications
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** Application
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== GlobalPlatform SCP02 initiation
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* mutual authentication between card and external software
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** contains random factor from both sides
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** generates session keys
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* transport-level security established ('secure messaging')
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* protected APDUs between on-card software and off-card software
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image::scp02-flow.png[align="center"]
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== GlobalPlatform SCP02 APDU commands
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* `INITIALIZE UPDATE`
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* `EXTERNAL AUTHENTICATE`
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* `BEGIN R-MAC SESSION`
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* `END R-MAC SESSION`
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== C-MAC
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* C-MAC (Command Message Authentication Code)
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** either on unmodified APDU or modified APDU
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image::scp02_cmac_modified.png[align="center"]
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== R-MAC
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optional MAC on responses generated by card
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image::scp02_rmac.png[align="center"]
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== Data Field Encryption
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optional confidentiality of data field of APDUs
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image::scp02_data_field_encryption.png[align="center"]
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== OTA (Over The Air)
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* Mechanism how some software in operator core can talk to SIM in the field
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* traverses the entire 3GPP Core and Radio Access Network, hence _over the air_.
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image::ota_overview.png[width=1000,align="center"]
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||||||
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== OTA transport mechanisms
|
||||||
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|
||||||
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* SMS-PP (SMS as you know it)
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||||||
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* SMS-CB (Cell Broadcast)
|
||||||
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** would require shared keys, bad idea
|
||||||
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* USSD
|
||||||
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** faster, more responsive than SMS
|
||||||
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* BIP (Bearer Independent Protocol)
|
||||||
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** CSD, GPRS, Bluetooth, IrDA
|
||||||
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* HTTP over TLS-PSK on the card (!)
|
||||||
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** Amendmend B GlobalPlatform Card Sepc v2.2
|
||||||
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|
||||||
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== Further Reading
|
||||||
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|
||||||
|
* https://git.osmocom.org/pysim/about/[pySim source code / git repository]
|
||||||
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* https://media.ccc.de/v/36c3-10737-sim_card_technology_from_a-z[Video of talk "SIM card technology from A-Z"]
|
||||||
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* Specs
|
||||||
|
** ETSI TS 102 221 (UICC)
|
||||||
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** ETSI TS 102 222 (Administrative Commands)
|
||||||
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** ETSI TS 102 223 (Bearer Independent Protocol)
|
||||||
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** ETSI TS 102 225 (Secured Packets for OTA)
|
||||||
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** 3GPP TS 31.102 (USIM)
|
||||||
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** 3GPP TS 31.103 (ISIM)
|
||||||
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** GlobalPlatform Card Specification 2.2.1
|
||||||
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** GlobalPlatform Secure Element Access Control v1.0
|
||||||
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|
||||||
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||||||
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== EOF
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