Security weaknesses of song´s advanced smart card based password authentication protocol

Password based authentication with smart cards has been adopted as a more secure means in insecure networks to validate the legitimacy of users. Traditional authentication schemes are based on the tamper-resistant smart card; that is, the data stored in the smart card cannot be revealed. However, it is a challenging problem for considering non-tamper-resistant smart cards used in user authentication. Very recently, in 2010, Song proposed an efficient authentication scheme with such non-tamper resistant smart cards based on symmetric key cryptosystems as well as modular exponentiations. In this paper, we will show that Song´s scheme is vulnerable to the offline password guessing attack and the insider attack. Besides, this scheme does not provide perfect forward secrecy and does not preserve user anonymity.