Search

With the advent of cloud computing, data privacy has become one of critical security issues and attracted much attention as more and more mobile devices are relying on the services in cloud. To protect data privacy, users usually encrypt their sensitive data before uploading to cloud servers, which renders the data utilization to be difficult. The ciphertext retrieval is able to realize utilization over encrypted data and searchable public key encryption is an effective way in the construction of encrypted data retrieval. However, the previous related works have not paid much attention to the design of ciphertext retrieval schemes that are secure against inside keyword-guessing attacks (KGAs). In this paper, we first construct a new architecture to resist inside KGAs. Moreover we present an efficient ciphertext retrieval instance with a designated tester (dCRKS) based on the architecture. This instance is secure under the inside KGAs. Finally, security analysis and efficiency comparison show that the proposal is effective for the retrieval of encrypted data in cloud computing.

Recently, how to retrieve the encrypted data efficiently from a cloud storage system becomes a hot topic. Public key encryption with keyword search (PEKS) can allow one to search the encrypted data with a keyword efficiently. Due to the booming of post-quantum cryptography, we propose public key encryption with keyword search from lattice assumption, which can resist quantum computer attacks. We delegate a particular cloud server to search the results, thus only the designated cloud server can finish the test process. Our scheme has been proved ciphertext indistinguishability in the standard model, which can reflect its security in the real world. To the best of our knowledge, our scheme is the first construction based on lattice in the standard model, which is a step stone in the post-quantum cryptographic communication.

With networking became prevalent, the amount of data to be stored and managed on networked servers rapidly increases. Meanwhile, with the improvement of awareness of data privacy, the user’s sensitive data is usually encrypted before uploading them to the cloud server. The searchable public-key encryption provides an efficient mechanism to achieve data retrieval in encrypted storage. Therefore, it is a critical technique on promoting secure and efficient cloud storage. Unfortunately, only few the existing schemes are secure to resist outside keyword guessing attacks. In this paper, we propose two efficient searchable public-key encryption schemes with a designated tester (dPEKS). One is a basic dPEKS, where the dPEKS ciphertext indistinguishability is proved without the random oracle. Meanwhile, the basic scheme is secure to resist the outside KGA since it satisfies the property of trapdoor indistinguishability. Comparing with the existing dPEKS schemes which use expensive pairing computation, our scheme is more efficient since we only need multi-exponentiation. Another is an enhanced dPEKS scheme. With the sender’s identity is kept secret from server, this scheme can provide stronger security.

In this paper, we present an effective fully homomorphic encryption (FHE) from ring learning with errors (RLWE) assumption without using Gentry’s standard squashing and bootstrapping techniques. Our FHE scheme is to modify the recent FHE scheme of Brakerski. We use the re-linearization technique to reduce the length of ciphertext considerably, and use the modulus reduction technique to manage the noise level and decrease the decryption complexity without introducing additional assumptions. Furthermore, with the key-homomorphic property, we extend our FHE scheme to a threshold fully homomorphic encryption (TFHE), which allows parties to cooperatively decrypt a ciphertext without learning anything but the plaintext. The TFHE scheme can be protected from related-key attacks, as long as we add extra smudging noise during sensitive operations.

In order to enhance the cleaning speed, reduce the cleaning cost and solve other problems of the existing cleaning equipment for blanket cylinder, we put forward a new-type unpowered cleaning equipment for blanket cylinder after a comparative analysis between powered spurt brush type cleaning equipment and unpowered cleaning cloth type cleaning equipment with respect to their structures and characteristics. Furthermore, after we study the cylinder structure of printing press and the cleaning effect of the existing cleaning equipments, a spurt brush type is proposed. We obtain the optimal pressure of this cleaning equipment through repeated experimental analyses on the pressure exerted by brush roller on blanket cylinder. The velocity parameter is determined by analyzing the cleaning principle of brush roller.

For paper forward unit of the current forward type flute laminating machine, the contact surface of the paper forward unit may damage paper during high speed paper forwarding. In view of this phenomenon, a solution is proposed through the study on the feeding unit of the flute laminating machine. In this paper, the corresponding sprocket driveshaft is controlled by a servo motor to slowly forward paper at the beginning and accelerate its forwarding speed gradually, until the entire feeding process is completed. In this way, the problem of paper pile-up and damages during the paper forwarding process can be solved, while matching backing paper feeding, so as to improve the feeding accuracy of the full-automatic flute laminating machine and hence its laminating accuracy.

Variable head sizes of paper roll will influence the stability of paper feeding device and hence the printing quality. Therefore, it is necessary to improve the printing quality by improving the stability of paper feeding device based on dynamic analysis on the phenomenon of variable head sizes of paper roll. It is found through dynamic analysis that the effect of variable head sizes on the support force of bearings is nearly five times that of the case when such effect does not exist. Vibration performance analysis of paper feeding device using finite element analysis obtains the natural frequencies of the first 6 orders for paper carriage and their dominant vibrational modes. This provides theoretical basis for the improvement of paper feeding device.

With the improvement of awareness of data privacy, the user's sensitive data is usually encrypted before uploading them to the cloud. The searchable public-key encryption with keyword search provides an efficient mechanism to achieve the encrypted data retrieval without the complicated key management of symmetric encryption. Therefore, it is a critical technique on promoting secure and efficient cloud storage. Unfortunately, only one existing construction of ciphertext retrieval scheme is secure against inside keyword guessing attacks (KGA). In this paper, we build a framework to resist insider attacks. Additionally, we propose an efficient ciphertext retrieval with keyword search scheme with a designated tester (dCRKS), which is secure against inside keyword guessing attacks (KGA). Our security proof and performance analysis demonstrate that our scheme is practical for retrieval data stored in the cloud server.

With the improvement of awareness of data privacy, the user's sensitive data are usually encrypted before uploading them to cloud. Searchable encryption is a critical technique on promoting secure and efficient cloud storage. In particular, publickey encryption with keyword search (PEKS) provides an elegant approach to achieve data retrieval in encrypted storage. All existing searchable publickey encryption schemes only provide the security based on classical cryptography hardness assumption. With the development of quantum computers, these schemes will be insecure. Based on the lattice hardness assumptions, we propose a new searchable publickey encryption scheme with a designated tester (dPEKS). Our scheme has advantages: First, our scheme is the first searchable publickey encryption scheme that is considered to be secure even if quantum computers are ever developed. Second, our scheme achieves the trapdoor indistinguishability. The trapdoor indistinguishability implies the security against outside offline keyword guessing attacks (KGAs). Last, our scheme can achieve the trapdoor anonymity for server.

Group signatures allow a group member to sign messages anonymously on behalf of the group. Generally, group signatures have anonymity, traceability and authentication. It has been well applied in practical distributed security communication environments. However, very few schemes can achieve the non-frameability and support dynamic membership management. In this paper, we propose a new group signature scheme. Our scheme achieves the non-frameability without the trusted issuer. Meanwhile, this scheme can support dynamic members join and revocation without incurring other secure threats. Furthermore, in our scheme, the size of group member's private key and the size of group public key are shorter than other schemes while the costs to be kept constant for signing and verifying. In particular, we prove that our scheme achieves anonymity, traceability and non-frameability under the random oracle model.