It's not just a phone number! If you own a smartphone, you will be assigned a lot of "numbers" [Yoshikawa's "smartphone is a little deeper"]

I think what you are most aware of when using a smartphone is the "phone number", and the smartphone uses a variety of "numbers" in addition to phone numbers. I'd like to introduce some below.

[1. Telephone number]

Up to now, smartphones are mobile phones, so they have been assigned phone numbers. Japanese mobile phones use 11-digit numbers starting from "090" and "080", but due to the recent increase in the number of contracts, the number has been exhausted, so new numbers starting from "070" have been used since November this year. In addition, the contractor is uniquely identified internally by a number called IMSI (International Mobile Subscriber Identity) (different from the telephone number).

携帯電話の番号といえばやっぱり電話番号

[2.SIM card number (ICCID)]

In current mobile phones, the contract information is stored in an IC card called SIM card (* 1). By setting this card on the terminal, mobile phone services can be used. The SIM card itself also has a 19-digit number called ICCID (IC card ID). Because it is the number of the SIM card, the ICCID will also change if it is replaced due to the size adjustment or loss of the SIM card.

* 1: strictly speaking, there are many names, such as "UIM", "USIM", "R-UIM" and so on, which are collectively referred to as SIM cards.

写真のSIMカードに記載されている「8981200」から始まる番号がICCID

[3. Terminal number (IMEI)]

The terminal itself also carries a number called IMEI (International Mobile Equipment Identity). In general, pressing "* # 0mm" on the phone screen will display IMEI. CDMA terminals (au terminals in China) use a number named "MEID" or "ESN".

IMEIは端末自身に割り振られる番号

[4. Identification number of mobile telephone network (MCC/MNC)]

MCC (Mobile Country Code) is the number that identifies the country and region, and MNC (Mobile Network Code) is the number that identifies the operator. In Japan, MCC is "440", MNC is NTT DoCoMo is "10", Softbank Corp. Mobile is "20" and so on.

[5.IP address]

If the phone number identifies the communication object in the telephone service, then the IP address identifies the other party in the network connection, such as Web or mail. IP addresses have version 4 (IPv4) addresses in the format "123.5.22.25" and "version 6" (IPv6) addresses in the format "2001:13a::32ea". IPv4, which is widely used today, theoretically has only 4.3 billion addresses, so there are no unused IPv4 addresses. Therefore, in the domestic mobile phone operators, multiple users share IPv4 addresses to save. Worldwide, the import of IPv6 that can ensure more addresses is being promoted, but the current situation is that few domestic mobile phones have been imported.

[6.MAC address]

Wireless LAN (Wi-Fi) devices and Bluetooth devices built into smartphones are assigned as MAC addresses (Media Access Control Address), such as inherent numbers such as "30:17:c8:00:00:00". They are used to identify each other through Wi-Fi and Bluetooth communication, respectively.

インターネット接続時にはIPアドレスとMACアドレスが利用される

[7.iOS/Android unique identifier]

The IOS device assigns a unique number called UDID (Unique Device Identifier) to all devices. Apple is often used in applications at first because it is easy to identify devices, but Apple forbids obtaining UDID from applications because of privacy concerns. Android has a similar "Android ID".

In addition, there are also the customer numbers for the internal management of customer information by mobile phone operators, the manufacturing numbers given by terminal manufacturers to each terminal, and so on. Although I inadvertently own a smartphone, I want to know that there are actually all kinds of "inherent numbers".

So, these summaries are shown in the table below.

No.	番号名	割り当て対象	変えられる？ （*2）
1	電話番号	携帯電話契約	変えられる（事業者の対応による）
2	ICCID	SIMカード	変えられないがSIMカードを交換すると変わる
3	IMEI	携帯電話端末	変えられない
4	MCC/MNC	携帯電話事業者（の設備）	変えられない
5	IPアドレス	インターネット接続中の携帯電話端末	その時々で勝手に変わる
6	MACアドレス	携帯電話端末のWi-Fi・Bluetoothデバイス	携帯電話の場合変えられない （*3）
7-1	UDID	iOS端末	変えられない
7-2	Android ID	Android端末	変えられないが変わる場合がある （*4）

* 2: irregular methods such as "rewriting terminal ROM" are not envisaged. * 3: there are also network devices that can change the MAC address. * 4: it is described in the developer documentation that "changes may occur when initializing to the factory state".

If you usually use a smartphone, you may not have the opportunity to realize that a number other than the phone number, especially in the smartphone app, this information is accidentally used. For example, consider the following usage.

Example 1) example 2) obtain the binding between MCC/MNC and SIM card to manage membership information

Such a feature may improve the convenience of the application, but on the other hand, because it is an "inherent number", it also contains concerns about compromising security and privacy. In fact, it is difficult for users to see when the application is using which number, but from a security and privacy point of view, it is important to know that there is such a number.

固有番号をアプリから取得できる（自作サンプルアプリで検証）

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In this sense, I'd like to introduce a variety of "slightly deeper places" for smartphones and tablets. Because I will write it down as briefly as possible, and please take care of me in the future.

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