The secret key is used both for encryption and for decryption. For a symmetric algorithm to be successful, the secret key must be known only to the sender and the receiver. The valid key sizes are specified by the particular symmetric algorithm implementation and are listed in the LegalKeySizes property.
If this property is null when it is used, the GenerateKey method is called to create a new random value.
Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)