Quick guide of IMEI, IMSI, ICCID and MSISDN numbers

IMEI Assigned to mobile phone.
IMSI, ICCID and MSISDN numbers are assigned to the SIM card.

IMEI

IMEI (International Mobile Equipment Identity) is a unique static identifier for mobile devices.
It’s used to identify individual mobile phones, as well as some satellite phones.
IMEI numbers are used by GSM networks to identify valid devices and can be used for various purposes,
including tracking lost or stolen phones and preventing unauthorised access to the network.

How to find IMEI in mobile phone ? In key pad type *#06#

The same information, ia available in about section of iphones.

Typically, the IMEI (International Mobile Equipment Identity) is a 15-digit code.
However, there are cases where it can be 14 or 16 digits long.
The structure of the IMEI number is standardized by the GSM Association, and it consists of the following components:

Type Allocation Code (TAC): The first 8 digits represent the TAC, which identifies the manufacturer and model of the device.
Serial Number (SN): The next 6 digits represent the serial number of the device.
Check Digit (CD): The last digit is a check digit used to verify the validity of the IMEI number

IMSI (International Mobile Subscriber Identity)

IMSI is assinged to the SIM card.

The IMSI (International Mobile Subscriber Identity) is a unique static identifier assigned to each mobile subscriber by mobile network operators.
It serves as a key identifier within the mobile network and is stored on the SIM (Subscriber Identity Module) card or equivalent module.
The IMSI is a critical component of the authentication and security mechanisms used in mobile networks.

The IMSI typically consists of three parts:

Mobile Country Code (MCC): A three-digit code that identifies the country where the SIM card was issued.
Mobile Network Code (MNC): A two- or three-digit code that identifies the mobile network operator within the country.
Mobile Subscriber Identification Number (MSIN): A variable-length number that uniquely identifies the subscriber within the mobile network.

When a mobile device connects to a mobile network, it sends its IMSI to the network for authentication and identification purposes.
The IMSI is used by the network to retrieve subscriber information from
the Home Location Register (HLR) or Authentication Center (AuC), verify the subscriber’s identity, and authorize access to network services.

While the IMSI itself is not typically transmitted over the air during normal operation to prevent eavesdropping, it is used internally by the mobile network for various purposes, including call routing, billing, and subscriber management.

IMSI is considered sensitive information and should be protected by mobile network operators to prevent unauthorized access and misuse.
Additionally, mobile devices and applications should adhere to privacy and security best practices to safeguard IMSI information and protect subscriber privacy.

TMSI (Temporary Mobile Subscriber Identity) is a temporary identifier used in mobile networks to enhance subscriber privacy and security.
Unlike IMSI (International Mobile Subscriber Identity), which is a permanent and globally unique identifier associated with each subscriber.
TMSI is periodically assigned and updated by the mobile network to prevent tracking and eavesdropping of subscriber communications.

The primary purpose of TMSI is to provide a level of anonymity for mobile subscribers while they are connected to the network.
Instead of transmitting the IMSI over the air during communication with the network, the subscriber’s device sends the TMSI.
This helps protect the subscriber’s identity and location from potential eavesdroppers or malicious actors.

Key points about TMSI:

Temporary Identifier: TMSI is temporary and can change periodically or in response to certain events,
such as handovers between different cells or re-registration with the network.

Assigned by the Network: TMSI values are assigned by the mobile network to individual subscribers.
When a subscriber registers with the network, the network assigns a TMSI for that session.

Local to the Network: TMSI values are local to the specific network where they are assigned.
They are not globally unique like IMSI values.

Enhances Privacy and Security: By using TMSI instead of IMSI for communication with the network, subscriber privacy and security are enhanced,
as the subscriber’s permanent identity is not exposed over the air.

Stored in SIM Card:
TMSI values are stored on the subscriber’s SIM card or equivalent module and are used by the device during communication with the network.

Overall, TMSI plays a crucial role in protecting subscriber privacy and security in mobile networks by providing temporary and anonymous identifiers for communication with the network.
It is an important component of the authentication and security mechanisms used in mobile communication protocols such as GSM, UMTS, and LTE.

The ICCID (Integrated Circuit Card Identifier)

is a unique identifier associated with the SIM (Subscriber Identity Module) card in a mobile device.
It is used to uniquely identify the SIM card and is composed of several parts:

Issuer Identifier: The first two digits of the ICCID represent the Issuer Identifier Number (IIN), which identifies the organization that issued the SIM card.

Individual Account Identifier: The next six to nine digits represent the Individual Account Identifier (IAI),
which uniquely identifies the SIM card within the issuing organization.

Check Digit: The last digit of the ICCID is a check digit used for error detection.

The ICCID is typically printed on the SIM card itself and can also be retrieved from the phone.

Go to Settings > General and tap About in phones and it will be there.

Industry code

This code identifies the card as belonging to the telecommunications industry.
It’s essentially the first two digits of the entire ICCID code.

ICCID (Integrated Circuit Card Identifier) will always start with 89.
This two-digit code functions as the industry identifier, signifying that the card is used in telecommunication networks.
It differentiates the ICCID from other types of chip cards, like credit cards or some government/business ID cards.

MSISDN

MSISDN stands for Mobile Station International Subscriber Directory Number.
In simpler terms, it’s your phone number in its international format, including the country code.

Here’s a breakdown of its functionality:

Mobile Station (MS): Refers to your mobile phone as a station on the cellular network.
International: Indicates it includes the country code for international calling.
Subscriber Directory Number: Identifies your specific subscription within the mobile network.

MSISDN Example: +94 71 234 5678

“+94” is the country code for Sri Lanka.
“71” is the national destination code for “Mobitel” within Sri Lanka. (Mobitel is a mobile network service provider in Sri Lanka)
“234 5678” is the subscriber number, which uniquely identifies the individual subscriber within Mobitel’s network

Refer https://www.youtube.com/watch?v=y8zi55BJGB4&list=WL&index=160 a good short video.