Symmetric encryption in the context of database encryption involves a private key being applied to data that is stored and called from a database. This private key alters the data in a way that causes it to be unreadable without first being decrypted.[17] Data is encrypted when saved, and decrypted when opened given that the user knows the private key. Thus if the data is to be shared through a database the receiving individual must have a copy of the secret key used by the sender in order to decrypt and view the data.[18] A clear disadvantage related to symmetric encryption is that sensitive data can be leaked if the private key is spread to individuals that should not have access to the data.[17] However, given that only one key is involved in the encryption process it can generally be said that speed is an advantage of symmetric encryption.[19]