A method of distributing a key to encrypt data for storing on a removable data storage item in a data transfer device library, the library comprising a controller having a key associated therewith and being connected to a plurality of data transfer devices each being operable to transfer data to a removable data storage item and having a key store, the method comprising: providing the key for the library to the controller; the controller providing the key to the key store of each data transfer device connected to the controller. A data transfer device library is also disclosed.