Taketsugu Yao

Reliable broadcast message authentication in wireless sensor networks

Due to the low-cost nature of sensor network nodes, we cannot generally assume the availability of a high-performance CPU and tamper-resistant hardware. Firstly, we propose a reliable broadcast message authentication working under the above-mentioned circumstances. The proposed scheme, although based on symmetric cryptographic primitives, is secure against anyone who knew the message authentication key as well as the malicious router nodes in multi-hop networks. The proposed scheme consists of three steps; (i) reliable broadcast of a message, (ii) legitimate acknowledgments from all the nodes in the network, and (iii) disclosure of the message authentication key. Secondly, we propose a way to reduce the amount of the stored information until the disclosure of the key, in which the server transmits the message integrity code of a message before transmitting the message. Finally, we consider the characteristic and the security issues of the proposed schemes.

Initial common secret key sharing using random plaintexts for short-range wireless communications

With the advent of radio frequency-based remote controls, we have to consider new security threats of eavesdropping and unauthorized controls in exchange for user-friendliness. Against these attacks, it is effective to encrypt and authenticate control commands. However, it will be a challenge to design how we establish a common secret key for encryption and authentication between a remote control and a controlled device. We propose new initial common key sharing protocol, which extends the over-the-air key transport in plaintext with suppressing the transmission power. Our proposed protocol increases the amount of transmission data by sharing the secret data to multiple random plaintexts, and makes it difficult for the eavesdroppers that are not located near the transmitter to obtain secret data by increasing the probability of the transmission error at the eavesdroppers. We evaluate the security level of our proposed protocol based on IEEE 802.15.4 specification, and show the relationships among the amount of transmission data, the bit error rate at eavesdroppers, and the number of trials to find the secret data through a brute force attack.