Masami Mohri

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In cloud-computing services, using the SSL/TLS protocol is not enough to ensure data confidentiality. For instance, cloud service providers can see the plaintext after the decryption at the end point of a secure channel. It is wise to introduce an encryption layer between the service client and the communication channel so the data will not be seen by the(More)
ICN/CCN advocates ubiquitous in-network caching to enhance content distribution. Non-safety application in vehicular communication is emerging beyond the initial safety application. However, it suffers from a typical issue of low delivery ratio in urban environments, where high buildings block and attenuate the radio propagation from RSU infrastructures as(More)
Ciphertext-Policy Attribute-Based Encryption (CP-ABE) is suitable for data access control on a cloud storage system. In CP-ABE, the data owner encrypts data under the access structure over attributes and a set of attributes assigned to users is embedded in user’s secret key. A user is able to decrypt if his attributes satisfy the ciphertext’s access(More)
Some time-stamping services are on business for protection of a document. A user can get the time-stamp just by connecting a terminal to the internet. However, if the user cannot connect to the internet, the document cannot be protected. Without regard to the internet access, if the user can get the time-stamp anywhere, time-stamping can use in many other(More)
Many physical devices and sensors make it possible to obtain more localized data and applications which provide more localized information for users will appear. Generally, those applications use a storage server for computing location-dependent data. Traffic of Internet of Things (IoT) devices may cause concentration, when data is stored into a server. It(More)
By exchanging the information on the status and the surrounding environment between devices, devices can determine the optimal action. We focus on the construction of a digital signature scheme for local broadcast, which allows the devices with limited resources to securely transmit broadcast messages. A multi-group authentication scheme that enables a node(More)
The malicious websites used by drive-by download attacks change their behavior for web client environments. To analyze the behavior of malicious websites, the singleenvironment analysis cannot obtain sufficient information. Hence, it is difficult to analyze the whole aspect of malicious websites. Also, the code obfuscation and cloaking are used in malicious(More)