Dan Yamamoto

Incrementally Executable Signcryptions

We present the concept of incrementally executable signcryptions, which is a generalization of traditional on-line/off-line signcryption and facilitates optimizing the sender’s off-line computation. With an incrementally executable signcryption scheme, the sender can activate signcryption process incrementally by its given sequential input: the sender’s key pair, a recipient’s public key, and a plaintext message to be sent to the recipient. Furthermore, we present an efficient generic construction of incrementally executable signcryption scheme. In our construction, the signing process can be done before being given the recipient’s public key as well as the message to be sent. This feature enables us to accelerate the subsequent processes. Moreover, our construction achieves the strongest security notions without relying on random oracles. In addition, it requires a weak assumption for the underlying signature scheme, i.e., the underlying signature scheme is sufficient to be unforgeable under generic chosen message attack. Furthermore, it supports the parallel un-signcryption feature, which allows receivers to perform two potentially expensive computations, i.e., the verification of off-line signature and the key-decapsulation, in parallel.

Cloud Security and Privacy Metamodel - Metamodel for Security and Privacy Knowledge in Cloud Services.

Security and privacy are important in cloud services. Numerous security and privacy patterns as well as nonpattern-based knowledge such as practices and principles exist in cloud services. Selecting and combining the appropriate knowledge is difficult due to numerous options and the nature of the layered cloud stack. Herein we propose a metamodel called the Cloud Security and Privacy Metamodel (CSPM) to handle security and privacy in cloud service development and operations. CSPM can classify and support existing cloud security and privacy patterns and practices in a consistent and uniform manner. Moreover, we propose a security and privacy aware process to develop cloud system utilizing CSPM. Several case studies verify the effectiveness and usability of our approach. As a result, we confirmed effectiveness and usability of CSPM, as well as some possible future work.

Secure ID management for social security and tax number system

The Japanese government will adopt the Social Security and Tax Number System. The system is beneficial, but it is necessary to consider how to prevent abuse of the system. To prevent any abuse of the system, we developed a secure device which manages IDs such as Social Security and Tax Number. This secure device safely manages IDs, and can increase efficiency of audit. In this paper, we evaluate the Japanese Social Security and Tax Number System by fault-tree analysis and summarise the proposed ID-management device.