APDU
Definition
Application Protocol Data Unit. The command and response message format used to communicate with a smart card over the ISO 7816 interface. Forensic SIM readers issue read-only APDUs (SELECT to navigate the file system, READ RECORD or READ BINARY to retrieve file content) without issuing write commands that would alter the card.
- Full name
- Application Protocol Data Unit
- Interface
- ISO 7816 smart card communication
- Forensic commands
- SELECT, READ RECORD, READ BINARY
- Forensic constraint
- Read-only APDUs used to avoid altering SIM card content
Common questions
Why do forensic SIM readers restrict themselves to specific APDU commands?+
Using only navigation and read commands avoids issuing write or update APDUs that would change the file system or data on the card, which preserves the evidentiary integrity of the original SIM rather than modifying it during extraction.
How does APDU structure relate to what an examiner actually recovers from a SIM?+
SELECT commands move through the card's hierarchical file system to reach a target elementary file, such as the SMS or contacts file, and the subsequent READ RECORD or READ BINARY commands then retrieve that file's raw content for the examiner to parse.
Related terms
- EF_SMS
- Elementary File for Short Message Service. A fixed-size record file on the SIM that stores SMS messages. Each record has a status...
- ICCID
- Integrated Circuit Card Identifier. The serial number of the physical SIM card itself, stored in EF_ICCID. It identifies the card as a...
- IMSI
- International Mobile Subscriber Identity. A 15-digit number stored in EF_IMSI on the SIM that uniquely identifies the subscriber account on the mobile...
- LOCI
- Location Information file (EF_LOCI on SIM, EF_LOCI and EF_EPSLOCI on USIM). Stores the Location Area Identity (LAI) last received from the network...
- UICC
- Universal Integrated Circuit Card. The physical hardware platform for modern SIM cards. A UICC can host multiple card applications simultaneously: a SIM...