Cheng-Ta Yang

Trading decryption for speeding encryption in Rebalanced-RSA

In 1982, Quisquater and Couvreur proposed an RSA variant, called RSA-CRT, based on the Chinese Remainder Theorem to speed up RSA decryption. In 1990, Wiener suggested another RSA variant, called Rebalanced-RSA, which further speeds up RSA decryption by shifting decryption costs to encryption costs. However, this approach essentially maximizes the encryption time since the public exponent e is generally about the same order of magnitude as the RSA modulus. In this paper, we introduce two variants of Rebalanced-RSA in which the public exponent e is much smaller than the modulus, thus reducing the encryption costs, while still maintaining low decryption costs. For a 1024-bit RSA modulus, our first variant (Scheme A) offers encryption times that are at least 2.6 times faster than that in the original Rebalanced-RSA, while the second variant (Scheme B) offers encryption times at least 3 times faster. In both variants, the decrease in encryption costs is obtained at the expense of slightly increased decryption costs and increased key generation costs. Thus, the variants proposed here are best suited for applications which require low costs in encryption and decryption.

A Pair-wise Key Establishment for Wireless Sensor Networks

Random key pre-distribution scheme is a flexible key management scheme for wireless sensor networks. Recently, numerous related studies have been proposed. However, most of them have weaknesses. First of all, sensors require large storage to store keys in order to maintain high connectivity. Secondly, impact caused by compromised sensors cannot be completely eliminated. In this paper, a novel pair-wise key establishment scheme based on the combination is proposed. Impact of key exposure from compromised sensors can be ignored since the pair-wise key for each pair of sensors is unique. Most significantly, we achieve the merit of fully connectivity without increasing storage requirement of sensors.