The following are some common rules and styles for generating ID numbers (or similar identification marks) in several countries or regions. Please note that the public structure information and sample numbers shared here are only used to illustrate the principle, not real and valid numbers. Please do not use them for any illegal purpose or forge identity documents. Different countries have different systems and algorithms. Only some cases are listed below: ──────────────────────── 【1. Chinese Resident Identity Card】 China currently uses the second-generation resident identity card number, which is 18 digits in total (the last digit may be a capital letter X). The meaning of each part is as follows: • The first 6 digits: area code, representing the location of the issuing authority (province, city, county level). • The next 8 digits: date of birth, in the format of YYYYMMDD (for example, 19491231 means December 31, 1949). • The next 3 digits: sequence code, usually used to distinguish people from the same region and the same date of birth, where odd numbers generally represent men and even numbers represent women. • The last digit: check digit, which is calculated by a specific weighted algorithm based on the first 17 digits. The possible results are 0 to 9 or the letter X. Example (randomly generated, not real information): 11010519491231002X means: 110105 represents a certain area; 19491231 is the date of birth; 002 is the sequence code; X is the check digit. The calculation method of the check digit is relatively public, and you can refer to the national standard GB 11643-1999. ────────────────────────── 【2. Swedish Personal Identification Number (Personnummer)】 Swedish personal identification numbers are usually in the form of 10 digits, often written as "YYMMDD-XXXX". Among them: • The first 6 digits represent the date of birth (year, month, day), and usually only the last two digits are taken to represent the year. • Of the last 4 digits, the last digit is the check digit, and the entire number is generally checked using the Luhn algorithm. For example: 850709-9805 Explanation: Born on July 9, 1985, the "5" in the following 9805 is a check digit calculated based on the other digits. Note: Different systems may have slightly different separators or reverse years, but the basic structure is as above. ────────────────────────── 【3. India's Aadhaar Number】 India's Aadhaar is a set of 12 digits based on a randomly assigned check digit calculated using the Verhoeff algorithm: • There are 12 digits in total, of which the last digit is a check digit calculated based on the previous 11 digits to prevent input errors. Example: 123456789012 (This example is purely a format demonstration and does not have any verification effect.) ────────────────────────── 【4. US Social Security Number (SSN)】 It should be noted that the United States does not have a national ID number, but the Social Security Number (SSN) is often used for identity identification. SSN is a 9-digit number with a traditional format of "three segments, such as AAA-GG-SSSS". Although some of the digits used to represent geographic areas or issuance times in the early days, the issuance standards of this type of number have changed since the mid-to-late 20th century. For example, the sample number: 078-05-1120 Note: This number is a famous historical sample number that has been widely used for demonstrations and should not be used in actual situations. ────────────────────────── 【5. Other countries】 Many countries and regions have their own ID card or identity coding system, and their structures vary. For example: • German Resident Identity Card (Personalausweis): The number is closely related to the machine-readable zone (MRZ) data and contains multiple checksums, but the specific algorithm and structure are not publicly available. • Korean Resident Registration Number: Usually 13 digits, such as "YYMMDD-XXXXXXX", some of which are used to encode the place of birth, gender and checksum; • Japan's "My Number": It is a 12-digit number, but the specific generation algorithm and allocation rules are mainly controlled by the government. ────────────────────────── 【Notes】 1. The above examples and descriptions are all structural analysis in the public domain. It is not supported to use this information to generate fake documents for fraud or illegal purposes. 2. The ID card numbers of many countries are subject to strict management and use regulations. Any attempt to tamper with, forge or abuse the ID card number may violate the law. 3. The algorithms and formats of various countries may be adjusted due to time and policy reasons. For specific questions, it is recommended to refer to the latest official documents. I hope the above information will help you understand the generation structure of ID card numbers in different countries. If you need more detailed algorithm details (such as the specific weighting factors and calculation process of the verification code algorithm of the Chinese ID card), you can further refer to the standards or official guidelines of the relevant countries.