Answer Description
PKI, or Public-Key-Infrastructure uses asymmetric encryption. There is a public key, and a private key, anything encrypted with a key can only be decrypted with the opposing key.
Wikipedia
Public-key cryptography, or asymmetric cryptography, is a cryptographic system that uses pairs of keys: public keys, which may be disseminated widely, and private keys, which are known only to the owner The generation of such keys depends on cryptographic algorithms based on mathematical problems to produce one-way functions Effective security only requires keeping the private key private the public key can be openly distributed without compromising securityIn such a system, any person can encrypt a message using the receiver's public key, but that encrypted message can only be decrypted with the receiver's private key This allows, for instance, a server to generate a cryptographic key intended for symmetric-key cryptography, then use a client's openly-shared public key to encrypt that newly-generated symmetric key
Public-key cryptography - Wikipedia, the free encyclopedia