A cryptographic method using asymmetric keys in which one key is made public while the other (the private key) is kept secure. Data encrypted with one key must be decrypted with the other. If the public key is used to encrypt the data, only the holder of the private key can decrypt it; therefore the data is secure from unauthorized use. If the private key is used to encrypt the data, anyone with the public key can decrypt it. Because only the holder of the private key could have encrypted it, however, such data can be used for authentication. See also digital certificate, digital signature.