def wsu_timestamp
      security_hash :wsu, "Timestamp",
        "wsu:Created" => (created_at || Time.now).utc.xmlschema,
        "wsu:Expires" => (expires_at || (created_at || Time.now) + 60).utc.xmlschema
    end
def wsu_timestamp
      security_hash :wsu, "Timestamp",
        "wsu:Created" => (created_at || Time.now).utc.xmlschema,
        "wsu:Expires" => (expires_at || (created_at || Time.now) + 60).utc.xmlschema
    end
Returns a Hash containing wsu:Timestamp details.