If something can be encrypted with a public key, why can’t someone just reverse engineer the encryption using the public key to get the original data?
In: Technology
Public key encryption relies on the fact that some math operations are more difficult than others. Multiplication is easier than division, squaring is easier than taking a square root, exponentiation is easier then taking a logarithm, etc.
In particular, it is very easy to multiply numbers, but incredibly difficult to factor them. How quickly can you factor 1147 by hand? There’s not really a fast way to do it other than just guessing every prime number until you get to the answer.
Encryption works by using extremely large prime numbers multiplied together, so large that factoring the result takes computers so long by brute force that it’s typically not worth it. It then uses some number theory properties of these numbers to generate a private key and public key, and those number theory manipulations are a pain in the butt to reverse engineer.
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