Summary The computing power of graphics processing units (GPU) has increased rapidly, and there has been extensive research on general‐purpose computing on GPU (GPGPU) for cryptographic algorithms such as RSA, Elliptic Curve Cryptosystem (ECC), NTRU, and Advanced Encryption Standard. With the rise of GPGPU, commodity computers have become complex heterogeneous GPU+CPU systems. This new architecture poses new challenges and opportunities in high‐performance computing. In this paper, we present high‐speed parallel implementations of the rainbow method based on perfect tables, which is known as the most efficient time‐memory trade‐off, in the heterogeneous GPU+CPU system. We give a complete analysis of the effect of multiple checkpoints on reducing the cost of false alarms and take advantage of it for load balancing between GPU and CPU. For GTX460, our implementation is about 1.86 and 3.25 times faster than other GPU‐accelerated implementations, RainbowCrack and Cryptohaze, respectively, and for GTX580, 1.53 and 2.40 times faster. Copyright © 2014 John Wiley & Sons, Ltd.

Devising a user authentication scheme based on personal identification numbers (PINs) that is both secure and practically usable is a challenging problem. The greatest difficulty lies with the susceptibility of the PIN entry process to direct observational attacks, such as human shoulder-surfing and camera-based recording. This paper starts with an examination of a previous attempt at solving the PIN entry problem, which was based on an elegant adaptive black-and-white coloring of the 10-digit keypad in the standard layout. Even though the method required uncomfortably many user inputs, it had the merit of being easy to understand and use. Our analysis that takes both the experimental and theoretical approaches reveals multiple serious shortcomings of the previous method, including round redundancy, unbalanced key presses, highly frequent system errors, and insufficient resilience to recording attacks. The lessons learned through our analysis are then used to improve the black-and-white PIN entry scheme. The new scheme has the remarkable property of resisting camera-based recording attacks over an unlimited number of authentication sessions without leaking any of the PIN digits.

Authenticated broadcast, enabling a base station to send commands and requests to low-powered sensor nodes in an authentic manner, is one of the core challenges for securing wireless sensor networks. μTESLA and its multilevel variants based on delayed exposure of one-way chains are well known valuable broadcast authentication schemes, but concerns still remain for their practical application. To use these schemes on resource-limited sensor nodes, a 64-bit key chain is desirable for efficiency, but care must be taken. We will first show, by both theoretical analysis and rigorous experiments on real sensor nodes, that if μTESLA is implemented in a raw form with 64-bit key chains, some of the future keys can be discovered through time-memory-data-tradeoff techniques. We will then present an extendable broadcast authentication scheme called X-TESLA, as a new member of the TESLA family, to remedy the fact that previous schemes do not consider problems arising from sleep modes, network failures, idle sessions, as well as the time-memory-data tradeoff risk, and to reduce their high cost of countering DoS attacks. In X-TESLA, two levels of chains that have distinct intervals and cross-authenticate each other are used. This allows the short key chains to continue indefinitely and makes new interesting strategies and management methods possible, significantly reducing unnecessary computation and buffer occupation, and leads to efficient solutions to the raised problems.