Journal:Informatica
Volume 26, Issue 2 (2015), pp. 181–198
Abstract
Abstract
This paper proposes an access control mechanism of verifiable cloud computing services using chameleon hashing and Diffie–Hellman key exchange protocol. By this mechanism, an entity can apply for cloud computing services and he can authorize other users to access granted data or services. When an authorized user or entity wants to access cloud computing services, he can authenticate the cloud computing service provider. Moreover, no entity secret will be revealed by data kept by cloud servers such that security and cost saving can be both ensured. Security proof under the simulation paradigm is also given.
Journal:Informatica
Volume 24, Issue 1 (2013), pp. 1–12
Abstract
Wireless communication techniques provide convenience for users to get desired information. Construction and management costs of information provision systems with low computational-ability devices, such as RFID devices, are low so lightweight authentication protocols are required for information security. In this paper, two lightweight authentication protocols are proposed for reliable information provision systems with low computational-ability devices. The first protocol is for public information, and the other ensures that only authorized users can get information.
Journal:Informatica
Volume 18, Issue 4 (2007), pp. 535–546
Abstract
In 2004, Abe et al. proposed a threshold signer-ambiguous signature scheme from variety of keys. Their scheme is a generalized case of the ring signature scheme, and it allows the key types to be based on the trapdoor one-way permutations (TOWP) or sigma-protocols including Schnorr's signature scheme. However, the signed message is public for all, which may result in disputes. In this paper, we present a novel threshold signer-ambiguous signature scheme, having the signed message concealed and keeping who the receivers are secret from variety of keys.
Journal:Informatica
Volume 16, Issue 4 (2005), pp. 503–518
Abstract
Recently, e-commerce becomes widespread; hence electronic department stores come into being. As a result, Chan and Chang proposed a scheme for digital gift certificates in 2002. Because it is hard to estimate the number of the clients of the electronic department stores, reducing the computation complexity of the electronic department stores becomes an important issue. Due to the need, we propose two schemes for digital gift certificates. Our proposed schemes are very practical since the computation load is light. So the schemes can be applied to the terminals with low computation power.