Efficient And Provable-Secure Certificateless Public Key Cryptosystems And Its Application

In the year of1976, Diffie and Hellman proposed the concept of Public Key Cryptography, which started a new direction of the cryptology. From then on, for satisfying the different security requirements, there were large numbers of public key cryptosystems to be presented and applied in all fields.In the traditional public key cryptosystem based on the public key infrastructure, the center authority issues the certificates to entities for ensuring the legality of public keys. However, in this system, it will face the problems of the update and expand of infrastructure, and the management of certificate, including the revocation, storage, distribution and verification, which places a huge energy and computational cost of the whole system. In order to remove this problem, Shamir proposed the identity based public key cryptography. In this primitive, the private key generator takes the identity of the user as a public key so that it enables to avoid the problem of certificate management. Nevertheless, the public and private key pair is generated by the private key generator alone and then results the key escrow problem. The entity must trust the trusted third party totally. Al-Riyami and Paterson put forward the certificateless public key cryptography to avoid the problems of certificate management and key escrow. In this cryptography, the user’s public and private key pair consist of the partial key from key generate center and the secret value from itself, and then the trusted third party cannot obtain the entity’s private key any more.The method of the security proof in the earlier public key cryptosystem provided the security judgment based on some assumption, and it would be secure if the scheme could not be broken in a long period. If there exists the security vulnerability, it revises the corresponding scheme and employs it continually. To go around and begin again, it raises the cost of the scheme and the concerns about the security. For avoiding this drawback, the researchers proposed the theory of the provable secure.In this paper, we focus on the provable secure certificateless public key cryptosystem and do some research as follows:1. Certificateless public key cryptography with bilinear pairing needs costly operations, which is not appropriate for a practical application. In this paper, we present a certificateless public key encryption scheme without bilinear pairing. This encryption scheme achieves Girault’s trust level3as in traditional public key infrastructure based cryptography and is proved to be secure in the random oracle model under the hardness assumption of computational Diffie-Hellman problem. The performance analysis and simulation show that our scheme is more efficient than other related schemes. Furthermore, based on this protocol, we also propose a scheme to protect the confidentiality and integrity of the transmitted information on the wireless sensor networks.2. Telecare Medicine Information Systems (TMIS) promote the traditional medical and healthcare services by information and communication technology. Since the physician and caregiver can monitor the patient’s real time physiological condition remotely in TMIS, this sensitive data transmitted in the public channel should be protected, which is the key issue in the Health Insurance Portability and Accountability Act. In this paper, we propose an efficient certificateless public key encryption scheme without bilinear pairing for TMIS. Our proposal is proved to be secure in the random oracle model under the hardness assumption of computational Diffie-Hellman problem. Moreover, after modifying the original model of the certificateless encryption, this scheme achieves Girault’s trust level3. Compared with the related protocols, the perform evaluations show that our scheme is more efficient and appropriate to collocate with low power mobile devices for TMIS. 3. Broadcast authentication is an efficient authenticated method, which enables a multitude of entities to verify the legality of the transmitted information and the data source. Some symmetric key based broadcast authentication schemes have been proposed to provide such services for wireless sensor networks, such as μTESLA and its variants.Unfortunately, these schemes all suffer from the Denial of Service attack due to the serious time delay in message authentication. In this paper, we propose a certificateless signature based broadcast authentication scheme without pairing. Moreover, this broadcast authentication scheme can reach Girault’s trusted level3and be proved to be secure in the random oracle under the hardness assumption of the discrete logarithm problem. Compared with the previous protocols, the perform evaluations show that this scheme is efficient and appropriate to be applied in wireless sensor networks with low power devices.