An aggregate signature scheme allows a public algorithm to aggregate n signatures on n distinct messages from n signers into a single signature. By validating the single resulting signature, one can be convinced that the messages have been endorsed by all the signers. Certificateless aggregate signatures allow the signers to authenticate messages without suffering from the complex certificate management in the traditional public key cryptography or the key escrow problem in identity-based cryptography. In this paper, we present a new efficient certificateless aggregate signature scheme. Compared with up-to-date certificateless aggregate signatures, our scheme is equipped with a number of attracting features: (1) it is shown to be secure under the standard computational Diffie-Hellman assumption in the random oracle model; (2) the security is proven in the strongest security model so far; (3) the signers do not need to be synchronized; and (4) its performance is comparable to the most efficient up-to-date schemes. These features are desirable in a mobile networking and computing environment where the storage/ computation capacity of the end devices are limited, and due to the wireless connection and distributed feature, the computing devices are easy to be attacked and hard to be synchronized.
A problem in the use of cryptographic mobile agents in the multilevel data warehouse environment is discussed. First, a systematic approach to cryptographic systems is presented. A cryptographic system is a collection of cryptographic primitives and protocols which help to ensure the confidentiality, integrity, and authenticity of data as well as secure key exchange for these primitives. Cryptography is a good tool for protecting sensitive data stored in data warehouses and transmitted through the corporate network. Mobile agents are intelligent programs that can migrate on a computer network. The authority of each agent can be established by way of cryptographic techniques.
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