How are public/private keys used in code? [closed]

Question

I have a question about public key encryption.

Say I have a string: "Hello, everyone."

If I am choosing to use a cipher to encode/encrypt this by just shifting the letters around X places, it is easy to figure out what the key is due to things in the english language like LL, OO, etc.

Taking a key into consideration, which could be a string or a number or whatever else, how does this incorporate into the code I'm writing to make my plain-text string encrypted in such a way that it isn't possible to discern patterns in the encrypted text?

Answer 1

You are using the term "cipher" with the meaning it had up to, say, 1860. While this would be quite appropriate in case of a quick chat with queen Victoria, it so happens that Science has advanced a tiny bit since these times.

Your question is is rather broad since it is, mostly: "that field of cryptography which has occupied thousands of researchers for more than four decades, well, how does it work ?". This cannot be answered within the size constraints of this site. Well, I can tell that "it works pretty well" but, beyond that, you are in need of some introductory material on cryptography. For instance, this book, which is not bad, as far as these things go.