Here is a link to a Microsoft web page:
https://technet.microsoft.com/en-us/library/aa998077(v=exchg.65).aspxUnderstanding Public Key Cryptography
For most of us, this is as much secrecy as we need. The Public Key method is easy to use and hard to crack. But it is not bullet proof.
... example, both the sender and the recipient must keep the key secret because anyone who knows the key can use it to decrypt and read the message. A lost key renders the encryption useless. In addition, the strength of the algorithm is important. An unauthorized party can take encrypted ciphertext and attempt to break the encryption by determining the key based on the ciphertext.
This subject is often considered controversial and should be avoided. IMO every user should have a basic knowledge of what this is and why it matters.
