Information Exchange on MANET for Efficient Evacuation

In disaster situations, people need to evacuate from dangerous areas to safe ones. In particular, they must formulate an evacuation plan for themselves when they cannot obtain support. Communicating with other evacuees to obtain information is useful in formulating an evacuation plan, and some studies have used a mobile ad hoc network (MANET) for this purpose, because such a network can be constructed using only wireless devices even when a fatal situation arises. However, we cannot treat a MANET in the same manner as other networks (such as a carrier network or Wi-Fi), and MANETs have several shortcomings in regard to information exchange. It is necessary to investigate the effects of these limitations on creating evacuation support systems on a MANET. We evaluated whether the limited information exchange available using a MANET is sufficient to create evacuation support systems through the use of a multi-agent evacuation simulator. As a result, our simulator showed that limited communication in which people communicate only with neighbors provides substantial efficiency for evacuation. People can continue to evacuate effectively even if they cannot obtain all of the desired information owing to MANET limitations.

Acceleration of Homomorphic Arithmetic Processing Based on the ElGamal Cryptosystem

In recent years, opportunities for using cloud services as computing resources have increased and there is a concern that private information may be leaked when processes data. The data processing while maintaining confidentiality is called secret computation. Cryptosystems can add and multiply plaintext through the manipulation of ciphertexts of homomorphic cryptosystems, but most of them have restrictions on the number of multiplications that can be performed. Among the different types of cryptosystems, fully homomorphic encryption can perform arbitrary homomorphic addition and multiplication, but it takes a long time to eliminate the limitation on the number of homomorphic operations and to carry out homomorphic multiplication. Therefore, in this paper, we propose an arithmetic processing method that can perform an arbitrary number of homomorphic addition and multiplication operations based on ElGamal cryptosystem. The results of experiments comparing with the proposed method with HElib in which the BGV scheme of fully homomorphic encryption is implemented showed that, although the processing time for homomorphic addition per ciphertext increased by about 35%, the processing time for homomorphic multiplication was reduced to about 1.8%, and the processing time to calculate the statistic (variance) had approximately a 15% reduction.

Implementation and Evaluation of Transport Layer Protocol Executing Error Correction (ECP)

Technologies for retransmission control and error correction are available for communications over the Internet to improve reliability of data. For communications that require the data reliability be ensured, TCP, which performs retransmission control, is often employed. However, for environments and services where response confirmation and retransmission are difficult, error correction technologies are employed. Error correction is generally implemented on UDP, but the existing framework implemented on UDP frequently does not consider the maximum frame size of the data link layer and relegates data division to the IP module. The IP module divides data according to the maximum size for the data link, and the receiving IP module reconstructs the divided data. For a data link layer typified by the current Ethernet with an error detection function, the frame is often destroyed upon error detection. At the IP module, the specification allows destruction of the entire dataset whenever divided data necessary for reconstruction is incomplete. Consequently, an error in a single bit results in a total loss of data handed to the IP module, and thus error correction performance declines with the increase in data size handed to the IP module. The present study considers the MTU of the data link layer and proposes error correction protocol (ECP) over IP, which decreases the transfer data volume flowing to the data link layer by dividing data into blocks of appropriate size based on designated error correction code and its parameters (thus improving error correction performance) and assesses the performance of ECP. Experimental results demonstrate that performance is comparable or better than existing error correction frameworks. Results also show that when a specification not ensuring the reliability of the data link layer was employed, error correction was superior to existing frameworks on UDP.