Asymmetric key encryption is a method of encryption which uses two complementary keys — a private key and a public key. Each recipient has a private key which is kept secret and a public key which is published. A sender uses the recipient’s public key to encrypt a message. The recipient uses its private key to decrypt the message.
The initiator only needs to protect the confidentiality and integrity of his or her private key. The public key can be distributed more freely, but its authenticity must be assured (e.g., guaranteed by binding the identity of the owner to that key).