Credit Cards - Breaking the Code: The maths behind bank numbers and the Luhn test

TL;DR

Credit card numbers use a specific encryption algorithm to ensure security and validity, making it difficult to create fake credit cards.

Transcript

credit cards use a rather similar idea similar encryption but it's a little different and we're gradually working towards an understanding of what is the general structure of all these things so probably your credit card um it may have a 12 or a 16 digigit form here's a 16 digigit form so I've just invented uh a number here and uh what we do is tha... Read More

Key Insights

• 💳 Credit card numbers are encrypted using The Loon test algorithm, which has been an industry standard since the 1950s.
• 🥇 The encryption algorithm involves doubling odd-placed digits and creating a weighted sum with even-placed digits.
• 🔂 The algorithm catches single-digit mistakes, typing errors, and most adjacent number swaps.

Questions & Answers

Q: How does the encryption algorithm for credit card numbers work?

The encryption algorithm, known as The Loon test, involves doubling odd-placed digits, summing the resulting digits if they are larger than nine, and creating a weighted sum by adding even-placed digits to a multiplier times the odd-placed digits.

Q: What happens if there is a transcription error or a typing mistake in a credit card number?

The encryption algorithm catches every single-digit mistake or mistyping of a number in a credit card. It also accounts for swapping adjacent numbers, except for a few cases like 09 and 90, ensuring the validity of the credit card number.

Q: Why is it important for the final sum in the encryption algorithm to be divisible by ten?

The final sum of the weighted digits and even-placed digits must be divisible by ten for the credit card number to be considered valid. This constraint ensures that the algorithm can detect any errors or fraudulent attempts to create fake credit cards.

Q: Can the encryption algorithm be used to validate credit card numbers?

Yes, the encryption algorithm can be used to validate credit card numbers. By applying the algorithm to a given credit card number, checking if the final sum is divisible by ten, one can determine if the credit card number is valid.

Summary & Key Takeaways

• Credit card numbers typically have a 12 or 16-digit form.

• The encryption algorithm used for credit card numbers, known as The Loon test, was created by Peter Loon in the 1950s and remains an industry standard.

• The algorithm involves doubling odd-placed digits, handling results larger than nine, summing the digits, and ensuring the final number is divisible by ten for validity.