Why Can't Hackers Crack Your Password?
Why Can't Hackers Crack Your Password? — Sometimes being "hard to undo" is itself the greatest strength. Prime numbers, studied out of pure curiosity for over 2,000 years, became the keys guarding the entire internet. Pure curiosity that once looked useless ended up changing the world.
When you buy a game item or send a message online, your information flies far across internet cables. What if someone steals a peek in the middle? Amazingly, that almost never happens. How does a computer keep secrets?
Keeping secrets is an ancient problem. Old generals swapped letters to hide messages from enemies. Rome's Caesar shifted every letter by three (A→D, B→E). But such codes broke easily once you knew the rule. The real problem was: how do you deliver the key safely? Get caught sending the key, and it's over.
Mathematicians had a clever idea: use numbers that are easy to multiply but extremely hard to reverse. Prime numbers divide only by 1 and themselves (2, 3, 5, 7, 11…). For example, 17 × 23 = 391 is quick. But going backward — "which two primes multiply to 391?" — takes far more effort. Computer encryption multiplies two enormous primes, hundreds of digits long, to build a lock. The product can be made public, because splitting it back into two primes would take even the fastest computer thousands of years!
- Online shopping and banking apps: card numbers protected by prime-based encryption (the 🔒 lock icon)
- Messengers like KakaoTalk: conversations encrypted
- The core technology behind cryptocurrencies like Bitcoin
- Digital certificates and e-signatures
密 (mil) means something hidden densely deep in the mountains (山) — the 密 of "secret." A code built from primes, as deep as a mountain and unbreakable, is exactly the math of 密.
Meet this hanja in Cheonjamun →Sometimes being "hard to undo" is itself the greatest strength. Prime numbers, studied out of pure curiosity for over 2,000 years, became the keys guarding the entire internet. Pure curiosity that once looked useless ended up changing the world.
