Is it possible to create a random alphanumeric password with built in error detection? [closed]
A friend told me about a giant alphanumeric password that he had to enter somewhere. Although he was initially worried that he would need multiple attempts due to typos. He was pleasantly surprised when the password text field actually showed an error message as soon as he typed in a single incorrect character.
If this system exists, how would it be possible? I haven't been able to find any description online or any research to explain it.
I could imagine that there could be a trade-off between introducing error detection and reducing entropy. E.g. if a password generator creates a 10 character alphanumeric password it would have 36 ^ 10 possible combinations. But if it always alternated numbers and letters, then there would be 2 * (26 ^ 5 + 10 ^ 5) possible combinations, and some typos could be detected. Could this idea be pushed further with more elaborate algorithm than swapping between numbers and letters?
I'm thinking of something like the Luhn algorithm for credit card numbers. A website can check a credit card number I enter and tell me if it is a valid number, without actually knowing if it's really my credit card number.
