The authenticity of a security document, such as a bank note, is verified by use of a security feature arranged in or on the document, which security feature comprises an antenna arranged to receive EM-radiation from an external energy source; a rectifier arranged to receive electric energy from the antenna and convert it into a rectified current; and an electrochromic display arranged to alter its electrochromic state in response to said rectified current. Hence, a security feature able alter its appearance in response to EM-radiation is provided, which comprises a display that can be given a large variety of two dimensional shapes.