The man-in-the-middle (MITM) attack is the major threat for handheld devices to agree on a session key in which they do not share any prior secret in advance, even if these devices are physically located in the same place. Apart from insecurely typing passwords into handheld devices or comparing long hexadecimal keys displayed on the devices' screens, many other human-verifiable protocols have been proposed in the literature to solve the problem. Unfortunately, most of these schemes are unscalable to more users. Even when there are only three entities attempting to agree on a session key, these protocols need to be rerun three times. In this paper, we present a bipartite and a tripartite authentication protocol using a temporary confidential channel. Besides, we further extend the system into a transitive authentication protocol that allows multiple handheld devices to establish a conference key securely and efficiently. In addition, we provide a formal proof to our protocol to demonstrate our scheme is indeed secure. We also implement the prototype of the system on a mobile phone with satisfying performance.

As new vulnerabilities on Windows systems are reported endlessly, it is more practical to stop polymorphic malicious code from exploiting these vulnerabilities by building an behavior-based monitor, rather than adopting a signature-based detection system or fixing these vulnerabilities. Many behavior-based monitors have been proposed for Windows systems to serve this purpose. Some of them hook high-level system APIs to detect the suspicious behaviors of code. However, they cannot detect malicious code that directly invokes Native APIs. In this paper, we present a novel security scheme that hooks Native APIs in the kernel mode. This method effectively prevents malicious code calling Native APIs directly. It introduces an average eight percent computation overhead into the system. Analyses and a series of experiments are given in the paper to support our claims.

Security issues become more and more significant in RFID development. Recently, Chien proposed an ultralightweight RFID authentication protocol in order to achieve privacy and authenticity with limited computation and transmission resources. However, we find two desynchronization attacks to break the protocol. In order to repair the protocol, two patches that slightly modify the protocol are presented in the paper.

Establishing trust between a group of individuals remains a difficult problem. Prior works assume trusted infrastructure, require an individual to trust unknown entities, or provide relatively low probabilistic guarantees of authenticity (95 percent for realistic settings). This work presents SPATE, a primitive that allows users to establish trust via mobile devices and physical interaction. Once the SPATE protocol runs to completion, its participants' mobile devices have authentic data that their applications can use to interact securely (i.e., the probability of a successful attack is 2-24). For this work, we leverage SPATE as part of a larger system to facilitate efficient, secure, and user-friendly collaboration via e-mail, file-sharing, and text messaging services. Our implementation of SPATE on Nokia N70 smartphones allows users to establish trust in small groups of up to eight users in less than one minute. The example SPATE applications provide increased security with little overhead noticeable to users once keys are established.

Several security protocols require a human to compare two hash values to ensure successful completion. When the hash values are represented as long sequences of numbers, humans may make a mistake or require significant time and patience to accurately compare the hash values. To improve usability during comparison, a number of researchers have proposed various hash representations that use words, sentences, or images rather than numbers. This is the first work to perform a comparative study of these hash comparison schemes to determine which scheme allows the fastest and most accurate comparison. To evaluate the schemes, we performed an online user study with more than 400 participants. Our findings indicate that only a small number of schemes allow quick and accurate comparison across a wide range of subjects from varying backgrounds.

Establishing trust between a group of individuals remains a difficult problem. Prior works assume trusted infrastructure, require an individual to trust unknown entities, or provide relatively low probabilistic guarantees of authenticity (95% for realistic settings). This work presents SPATE, a primitive that allows users to establish trust via device mobility and physical interaction. Once the SPATE protocol runs to completion, its participants' mobile devices have authentic data that their applications can use to interact securely (i.e., the probability of a successful attack is 2-24). For this work, we leverage SPATE as part of a larger system to facilitate efficient, secure, and user-friendly collaboration via email and file-sharing services. Our implementation of SPATE on Nokia N70 smartphones allows users to establish trust in small groups of up to eight users in less than one minute. The two example SPATE applications provide increased security with no overhead noticeable to users once keys are established.

Recently, Bertino et al. proposed a new time-bound key management scheme for broadcasting. The security of their scheme is planted on the hardness breaking of elliptic curve discrete log problem, HMAC, and tamper-resistance devices. They claimed that as long as the three assumptions hold, their scheme is secure. By means of secure, users cannot access resources that they are not granted, even if users collude. In this paper, we demonstrate that this scheme is insecure against the collusion attack. We also provide some possible amendments to this scheme.

In 2007, Kim et al. proposed a secure compression code called the secure arithmetic code (SAC). The code was claimed to be secure against chosen plaintext attacks. However, we find that the SAC is not as secure as the authors have claimed. In this paper, we show the code is prone to two attacks. The first attack completely breaks the code using an adaptive chosen plaintext attack with a polynomial number of queries. The second attack is a ciphertext-only attack, which removes a part of the output permutation.