Recently, Wang, Liu, Xiao and Dan proposed an efficient and secure dynamic ID-based remote user authentication scheme and claimed that their scheme provides strong security. We demonstrate that Wang et al.’s scheme is vulnerable to insider, masquerade and server spoofing attacks.
Password based authentication schemes have been widely used to verify the legitimacy of a user over an insecure communication channel. A common feature among most of the published schemes is that user's identity (ID) is static in all the transaction sessions, which may leak some information about the user and can create risk of identity theft during message transaction. Therefore, to provide user anonymity, many dynamic ID based remote users authentication schemes have been proposed. Recently, Khan et al. proposed an efficient and secure dynamic ID based remote user authentication scheme and claimed that their scheme can provide strong security against various attacks. In this paper, we have demonstrated that Khan et al.'s scheme is vulnerable to server spoofing attack and insider attack, and has some flaws in login and authentication phase as well and also proposed an enhanced scheme to overcome the identified weaknesses.
In 2009, Liao and Wang proposed a secure dynamic ID based remote user authentication scheme for multi-server environments. They achieved user anonymity by using secure dynamic IDs instead of static IDs. Recently, Hsiang and Shih proposed an improved scheme to fix the security flaws found in Liao-Wang’s scheme. Hsiang and Shih claimed that their scheme maintains the benefits and increases the security of Liao-Wang’s scheme, while providing mutual authentication that Liao-Wang’s scheme lacks. In this paper, however, it is shown that Hsiang-Shih’s scheme cannot withstand user and server impersonation attacks. Their scheme is thus vulnerable to malicious users and insecure for practical applications.
In 2011, Khan et al. analyzed and improved an enhanced secure dynamic ID-based remote user authentication scheme to overcome the weakness of Wang et al.’s scheme. In 2013, Young-Hwa An showed that Khan et al.’s scheme is not secure because Khan et al.’s scheme can not resist password guessing attack, forgery attack and does not provide user anonymity. After that he proposed a security improvement of dynamic ID-based remote user authentication scheme with session key agreement to remedy the weakness in Khan et al.’s scheme. Recently, through our study, we have found that Young-Hwa An’s mechanism is not secure enough. There still exists insider user’s attack, anonymity attack and forgery attack.
Remote user authentication is an essential part in electronic commerce to identify legitimate users over the Internet. However, how to protect user privacy in the authentication has become an important issue recently. Therefore, many secure authentication schemes with smart cards have been proposed. In this paper, we will analyze the security weaknesses of two recently proposed authentication schemes for preserving user privacy. First, Chang et al. (2011) proposed a robust and efficient remote user authentication scheme to provide user anonymity. However, this scheme fails to protect user privacy in terms of anonymity and traceability. In addition, it is vulnerable to the server counterfeit attack and it does not provide perfect forward secrecy for session keys. Furthermore, if the smart card is lost, it will suffer from the offline password guessing attack as well as the user impersonation attack. Second, Wen and Li (2012) recently presented an improved dynamic ID-based authentication scheme with key agreement. However, this scheme is vulnerable to traceability. In addition, it does not support perfect forward secrecy for session keys. Furthermore, the insecure offline password change phase and online secret renewal phase will result in the denial of service attack.
Summary. In 2012, Wen and Li proposed a secure and robust dynamic identity based remote user au-thentication scheme with key agreement using smart cards. They claimed that their scheme is efficient and secure. But in this paper, we demonstrate that their scheme is completely insecure and vulnerable to various known attacks like offline and online password guessing attack, impersonation attack, server mas-querading attack, denial of service attack and an insider attack. Also we point out that there are loopholes in password change phase and online secret renew phase which leads to the desynchronization between user and the server and even the legitimate user is rejected by the server. In addition, an adversary can easily generate the common session key of further transmission between user and the server. Thus the entire system collapses and authors claims are proven to be wrong and their scheme will not be secure and efficient for practical purpose.