Some days you can’t love social media enough. This is one of those days. It began like this. Someone stole 12 tons of KitKats.
And then the replies started coming in. Scroll down.
Take your card number and starting from the second-to-last digit, double every second digit moving left. If doubling a digit produces a number greater than nine, subtract nine from the result. Then add all the digits together, the doubled ones and the untouched ones. If the total is divisible by ten, the number is valid. If it isn’t, the number is mathematically impossible as a card number and the form rejects it on the spot.
This is the Luhn algorithm written in 1954 by a computer scientist at IBM named Hans Peter Luhn. It still runs inside every payment form on the internet today. And it turns out that valid card numbers are not random. They follow this mathematical rule, and any number that breaks it is immediately disqualified without ever touching a bank’s systems. No server contacted. No database checked. No network request made. The validation happens entirely on your device, in milliseconds.
The first six digits do additional work before the Luhn check even runs. They are called the Issuer Identification Number; the first digit identifies the card network (4 means Visa, 5 means Mastercard, 3 means Amex), and the following digits identify the specific bank that issued the card. This is why payment forms show you the Visa or Mastercard logo the moment you type the first digit. No server needed. The network is encoded in the number itself.
The last digit of every card number is called the check digit it exists for no other purpose than to make the entire number pass the Luhn algorithm. When a bank generates a new card number, it calculates what the last digit must be to make the sequence valid, then stamps it on the card. It is a built-in mathematical fingerprint.
Miringa, a Kenyan boy creating a ‘People’s IEBC’ to prevent any form of rigging, has come up with a way for Kenyans to beat the government at its own game if it tries to switch off the internet!
A speed reading training video starts at 300 words per minute and ends at 900 words per minute.
I was able to understand this entire video the first time it was present.
Could you?
Imagine a world without music.
We’d prolly be listening to waves wash on the beach, or wait for thunder so that we can drop that banger dance move.
And the end of the year, someone’s Spotify wrapped top album would still be “toilet flushing”???
Pain💀