function readEncriptionData(callback) {
            self.getXmlFileDom('META-INF/encryption.xml', function (encryptionDom, error) {

                if(error) {
                    console.log(error);
                    console.log("Document doesn't make use of encryption.");
                    _encryptionHandler = new EncryptionHandler(undefined);
                    callback();
                }
                else {

                    var encryptions = [];


                    var encryptedData = $('EncryptedData', encryptionDom);
                    encryptedData.each(function (index, encryptedData) {
                        var encryptionAlgorithm = $('EncryptionMethod', encryptedData).first().attr('Algorithm');

                        encryptions.push({algorithm: encryptionAlgorithm});

                        // For some reason, jQuery selector "" against XML DOM sometimes doesn't match properly
                        var cipherReference = $('CipherReference', encryptedData);
                        cipherReference.each(function (index, CipherReference) {
                            var cipherReferenceURI = $(CipherReference).attr('URI');
                            console.log('Encryption/obfuscation algorithm ' + encryptionAlgorithm + ' specified for ' +
                                cipherReferenceURI);
                            encryptions[cipherReferenceURI] = encryptionAlgorithm;
                        });
                    });
                }

            });
        }
Determine whether the media assets (audio, video, images) within content documents require special
programmatic handling.
@returns {*} true if content documents fetched using this fetcher require programmatic fetching
of media assets. Typically needed for zipped EPUBs.

false if paths to media assets are accessible directly for the browser through their paths relative to
the base URI of their content document.