Security Analysis of Server-Aided Public Key Generation Protocols on Low-Power Devices for Ad-Hoc Networks

In ITST2006, Chen et al. presented two server-aided public key generation protocols for low-power devices and claimed that their protocols secure against collusion attack. In this paper, we point that if the servers collude with each other, those servers could obtain low-power devices' secret information, and they can get the plaintext from any ciphertext. We also present an improved server-aided standard RSA key generation protocol against the collusion attack.

1. Introduction

In some real-time applications, handheld devices such as cell phone, Mp3, PDA need to do complex work (scientific computation, prime generation, etc.). For instance, a cell phone wants to generation a RSA modulus in public key cryptosystems. However, those handheld devices have very limited computing power and will cost much time to do such work [1]. It is desirable for us to improve the computation performance on the handheld devices. Taking account of the mobility and security, we will employ untrusted servers to offload heavy work. In those server-aided computations, security is important. This means that the auxiliary servers should not obtain any confidential information of the low-power devices.