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he magic of Luhn's algorithm: Why this simple formula can protect your credit card securit
Credit cards have become a ubiquitous payment method in our daily lives. However, as the use of credit cards increases, problems also arise, especially in identifying validity and avoiding errors. At this time, the emergence of the Luhn algorithm brought a solid line of defense to our payment system.
Introduction to Luhn Algorithm
The Luhn algorithm, also known as the modulo 10 algorithm, was originally proposed by IBM scientist Hans Peter Luhn in 1960. This is a simple checksum calculation formula used to verify the validity of various types of identification numbers, especially credit card numbers. The algorithm is specified in the ISO/IEC 7812-1 standard and is public domain knowledge.
This algorithm is designed to protect users from accidental input errors, not to protect against malicious attacks.
How the Luhn algorithm works
The basic logic of the algorithm is to remove the last digit (check digit) of the number to be verified, and then double every second digit from right to left. If the doubled result is greater than 9, subtract 9. All processed digits are added together and the calculated sum is then subjected to a modulo 10 operation to obtain the check digit.Example of Check Bit Calculation
For example, given an account number 1789372997 (without the check digit), the check digit can be calculated using the following steps. First, all the numbers are processed, and finally the calculated value can be checked to see if it matches the original check digit. This can effectively verify the validity of the number and prevent errors.
Strengths and weaknesses
The advantage of Luhn's algorithm is that it can detect all single errors, as well as almost all transpositions of adjacent numbers. For example, if a single digit is wrong, the algorithm will recognize it immediately. However, the algorithm is not effective against certain specific input errors, such as transposing 09 and 90.
Also, although the Luhn algorithm can identify most errors, its detection capability is still inferior to other complex checksum algorithms, such as the Verhoeff and Damm algorithms.
Application Scope
The Luhn algorithm is not limited to credit card verification, but is also widely used in other identification number systems. For example, the US National Provider Identification Number, Canadian Social Insurance Number, Israeli ID Number, etc. are all checked using this algorithm.
Conclusion
Luhn's algorithm is almost indispensable in our digital world. Next time you use a credit card to pay, will you think about how this algorithm is protecting your security?
