NSXMLParser get MD5 of XML

using AFNetworking i'm loading a XML from a webservice. Is it possible to generate the MD5 of the XML-String?

AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];
manager.responseSerializer = [AFXMLParserResponseSerializer new];

NSDictionary *parameters = @{@"code": dayString};

[manager POST:kWWEventSeminarServiceURL parameters:parameters success:^(AFHTTPRequestOperation *operation, id responseObject) {
    NSXMLParser *XMLParser = (NSXMLParser *)responseObject;

    // How to get the MD5 here?

    [XMLParser setDelegate:seminarParser];

    [XMLParser parse];

} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
    NSLog(@"Error: %@", error);
}];