There is often no unified global standard for passport numbers in different countries. Instead, they are designed by passport management agencies in each country based on their own internal security requirements and management software systems. The following are some common principles and examples in public literature for academic research or understanding system design ideas, but please note the following points: 1. Security and confidentiality: In order to prevent counterfeiting or abuse, many countries will not disclose detailed internal generation rules. The public information usually only involves the outline of the format or verification algorithm. Any attempt to use this information to produce false documents is illegal. 2. ICAO standards for machine-readable passports (MRP): The International Civil Aviation Organization (ICAO)'s "9303" (Machine Readable Travel Documents) provides guidance on the basic content and verification methods of machine-readable passports. For example, a passport number usually comes with a verification code in the machine-readable zone, and its calculation method is roughly as follows: a. Convert each character to a numeric value. The numbers 0 to 9 represent themselves, the letters A to Z are usually converted to 10 to 35, and filler characters such as "<" are assigned a value of 0. b. The corresponding characters are multiplied by the weights in sequence, and the weights are repeated in the sequence of 7, 3, and 1. c. All the products are summed and modulo 10, and the result is the check digit. This method is used to ensure the integrity of the passport number during data transmission. 3. Example description (Note: The following numbers are fictitious examples, only used to introduce the format and verification principle, and do not represent any real passport): [Example 1] Full digital passport number Assume that a country uses 9-digit passport numbers, such as 123456789. Assuming that they attach a check digit to the passport number, the calculation process may be: – Give weights: 7, 3, 1, 7, 3, 1, 7, 3, 1 (from the first to the ninth digit) – Multiply each digit by the corresponding weight and sum: 1×7 + 2×3 + 3×1 + 4×7 + 5×3 + 6×1 + 7×7 + 8×3 + 9×1 = 7 + 6 + 3 + 28 + 15 + 6 + 49 + 24 + 9 = 147 – 147 mod 10 = 7 Then the passport number part of the complete machine-readable information may be written as 1234567897 (the last digit 7 is the check digit). Note: Whether to add a check digit directly to the passport number and what method to use are different in different countries. [Example 2] Passport number with letters and numbers Some countries may design it to start with 1-2 letters, followed by numbers. For example, "C1234567". If a similar verification algorithm is used, the letters need to be mapped to numerical values according to the regulations (such as C→12 if numbering is A=10), and then the weights are used to calculate the checksum. For example: Number: C1234567 Character mapping: C→12, 1→1, 2→2, 3→3, 4→4, 5→5, 6→6, 7→7 Assume that the weight sequence is 7,3,1,7,3,1,7,3 (for example only) Calculate the sum: 12×7 + 1×3 + 2×1 + 3×7 + 4×3 + 5×1 + 6×7 + 7×3 = 84 + 3 + 2 + 21 + 12 + 5 + 42 + 21 = 190 Checksum: 190 mod 10 = 0 Therefore, the full number may be C12345670. However, it must be emphasized that different countries may use completely different formats and verification rules. 4. Actual situation in various countries: For example, the passport number formats of the United States, the United Kingdom, Canada and other countries are different. Some are pure numbers, some are mixed letters and numbers, and the check code may not be directly displayed in the passport number. The encoding of Chinese passports also has its own rules (for example, it may distinguish between diplomatic, official and ordinary passports), but the specific internal rules and details are not fully disclosed. Summary: Although there is an ICAO-specified verification method as a common technology (especially in the machine-readable area), the compilation of passport numbers involves security, anti-counterfeiting design and internal management needs in addition to data integrity. Therefore, all countries may make adjustments and expansions based on the public format. The above examples and algorithms are for demonstration purposes only and should not be used for any illegal activities.