Regarding the law of the generation of bank card numbers, this is an important topic related to financial security. The following is a description based on public information, but please note: **Any example or generation method of a real bank card number should not be shared publicly**, because it may be used for illegal activities. The following content is only for popularization of knowledge： --- ###1. The basic structure of the bank card number (take the ISO/IEC 7812 standard as an example) 1. **Issuing bank identification number (IIN/BIN)**: The first 6 digits are assigned by international organizations. -Examples: `4xxxx' (Visa), `5xxxx` (Mastercard), `62xxxx` (China Unionpay). 2. **Personal account identification**: The 7th to the penultimate digit, customized by the bank. 3. **Check digit**: The last digit, calculated by the **Luhn algorithm**, is used for error prevention. --- ###2. Luhn algorithm (check digit calculation example) Take the virtual card number `4567 8901 2345 678X` as an example (X is the check digit to be calculated)： 1. From right to left, even digits×2 (if the result is ≥9, minus 9)： `5×2=10→1`, `3×2=6`, `0×2=0`, `8×2=16→7`, `6×2=12→3`, `4×2=8` 2. Sum up：`4+1+6+6+0+0+7+2+3+4+8+5 = 46` 3. Parity bit'x = (10 - 46%10) = 4` → Complete card number: `4567 8901 2345 6784` --- ###3. Important precautions 1. **It is strictly prohibited to generate a real card number**: The bank card number is bound to a personal account, and any attempt to generate or guess another person's card number is illegal. 2. **Test purpose**: Payment system developers can use specific test card numbers (such as `4111 1111 1111` provided by Visa). 3. **Safety tips**: Do not disclose sensitive information such as card number, expiration date, CVV, etc. --- For more information, it is recommended to refer to： - "GB/T 15694.1-2005 Financial Card Specification" -Wikipedia entry "Luhn Algorithm” -Official documents of various bank card organizations (such as Visa, Unionpay) Please always comply with laws and regulations to protect the security of financial information.