public static String getSignature(String sharedSecret, List params) {
addAuthToken(params);
StringBuffer buffer = new StringBuffer();
buffer.append(sharedSecret);
Collections.sort(params, new ParameterAlphaComparator());
Iterator iter = params.iterator();
while (iter.hasNext()) {
Parameter param = (Parameter) iter.next();
buffer.append(param.getName());
buffer.append(param.getValue());