RSA Cryptography

Imagine a padlock anyone can snap shut, but only you can open. You publish the open lock far and wide; anyone locks their message and sends it, and only your private key undoes it. This is RSA — the public-key system invented in 1977 and still protecting HTTPS, email, and banking. Its security rests on one asymmetry: multiplying two primes is easy; recovering them from the product is not.