For public-key encryption, the key is published to the world while keeping the private key secret. Anyone with a copy of the public key can then encrypt information that only the recipient can read, even people the recipient has never met. The primary benefit of public-key encryption is that it allows people who have no preexisting security arrangement to exchange messages securely. The need for sender and receiver to share secret keys via some secure channel is eliminated; all communications involve only public keys, and no private key is ever transmitted or shared.