Security & applets

Secure the SIM layer. Then put logic on the card.

Two services. Keys that never leave the site — and a security read of the card, including the electrical profile.

Our services

Two pieces of work

On-site key generation

Build the whole chain — how OPC/Ki and OTA keys are born, who holds which secret, HSM, what to avoid — on the operator's site. Consulting on that ceremony is part of the same job. The point of on-premise is that those keys do not go out.

SIM security and electrical profile

Overview of SIM security — including against regulation where that is the requirement — and design of the electrical profile: file structure, access (PIN / PUK / ADM / ARR), and OTA keysets.

Electrical profile

Three kinds of file. Folders around them.

A SIM is a smart card: it hides a key and proves it has it. The electrical profile is how that computer is laid out — not a mystery name, a filesystem. ETSI TS 102 221. The longer walkthrough starts from why the card exists at all.

Electrical profile — ETSI TS 102 221 §8.2

MF 3F00 Master file root of the card

EF ICCID Transparent one blob — the serial

DF TELECOM Folder phonebook, SMS, last numbers

EF ADN Linear fixed records: a phonebook table

EF LND Cyclic records circle read/write — last numbers dialled

ADF USIM Application a network identity lives here

EF IMSI Transparent the subscriber identity

EF ARR Linear fixed who may read or write each file

Transparent
One stretch of bytes. Read or write by offset — like a single document.

IMSI, ICCID
Linear fixed
Equal-length records, addressed by number — like rows in a table.

Phonebook (ADN), ARR
Cyclic
Still records — same as linear. Read and write go in a circle: the newest write overwrites the oldest. TS 102 221 §8.2.2.3.

Last numbers dialled (EF LND)

Access: PIN1 · PIN2 · PUK1 · PUK2 · ADM · ARR per file OTA keyset (SCP80): KVN '01'–'0F' · KIc + KID + DEK/KIK · TS 102 225 annex A SCP81 (HTTP): PSK-TLS + DEK, typically KVN '40'–'4F' · GP Amendment B / SGP.02

Applets

What runs on the card

Traditional

Multi-IMSI

Switch identity when roaming is thin. We build yours — not a product checkbox.

Build your own Multi-IMSI — contact

Traditional

IMEI lock

Bind a SIM to a piece of hardware. Fraud learned to fake the IMEI — so this is not the whole story.

Discuss an IMEI lock

Free STK tool

Terminal Profile analyser

When a SIM meets a device: Reset → ATR (the card answers) → Terminal Profile (the handset declares what it can do). An applet reads that profile. No IMEI needed.

Why it matters · Parse a profile online · Source on GitHub

Contact

Discuss keys, a profile, or an applet

Email direct: [email protected]

Include the network or estate, the SIM vendors, and what the campaign needs to do. A technical call is 30 minutes, engineering to engineering.

Enquiries are handled as in the privacy notice. Do not paste production keys.