String contentMD5 = getHeader(cr, "Content-MD5");
String contentType = getHeader(cr, "Content-Type");
String date = getHeader(cr, "Date");
if (date == "") {
date = new RFC1123DateConverter().format(new Date());
cr.getHeaders().add("Date", date);
}
// build signed string
String stringToSign = requestMethod + "\n" + contentMD5 + "\n"