public key
In cryptography, a public key is a large numerical value that is used to encrypt data. The key can be generated by a software program, but more often, it is provided by a trusted, designated authority and made available to everyone through a publicly accessible repository or directory.
A private key is another large numerical value that is mathematically linked to the public key. In asymmetric cryptography, whatever is encrypted with a public key may only be decrypted by its corresponding private key and vice versa.