The purpose of privacy-preserving spam filtering is to inspect email while preserving the privacy of its detection rules and the email content. Although many solutions have emerged, they suffer from the following: 1) Theprivacyprovided is insufficient as the email content or detection rules may be exposed to third parties; 2) Due to improper use of encryption, exhaustive word search attacks are possible, potentially breaking theconfidentialityof encrypted emails; 3) When spam filtering is outsourced, email is given to the outsource, whereuser privacy may be compromisedif privacy protection measures are not properly put in place; 4) Confirmation of whether the encrypted email is spam is only determinedafterthe receiver receives the email, which can lead to a situation in which spam is loaded to the memory of the receiver’s terminal for spam filtering. This can be harmful, for example, when an attacker inserts a web browser vulnerability into the body of an email to lure users to a phishing site simply by reading the email; 5)Computationally expensive operationsare unavoidable to provide required features of privacy-preserving spam filtering. We present Privacy-preserving Content-based Spam Filter (PCSF), which is a spam filter system that does not suffer from the aforementioned issues. Additionally, our system providespre-validationbefore the receiver reads the email. We provide an implementation of our system based on the Naive Bayes spam filter and prove its security.

The field of cryptography has endeavored to solve numerous security problems. However, a common premise of many of those problems is that the encryptor always generates the ciphertext correctly. Around 10 years ago, this premise was not a problem. However, due to the rapid development and the use of the cloud, which has introduced various access policies and functionalities to provide higher security, it is not correct to assume that this premise is always applied. A “Fake Policy Attack”, which we introduce in this article, is an attack that incorrectly sets the access policy of the ciphertext against the system rules so that users who do not meet the rules can decrypt the ciphertext. In other words, it is an attack that ignores the rules of the system and eventually breaks the security and leaks information. This attack can be more critical for the application environments that require strong security not to leak any related information about ciphertext. In this article, we demonstrate the possible threat of the Fake Policy Attack by providing two relevant examples. Then, we propose a scheme called Policy Authenticable ABE (PA-ABE) to resolve this issue. We provide a formal security analysis of the proposed scheme and performance evaluation results based on our implementation.

Abstract Recently, a lot of researches focused on identity‐based encryption (IBE). The advantage of this scheme is that it can reduce the cost of the public key infrastructure by simplifying certificate management. Although IBE has its own innovations, one of its weaknesses is the key escrow problem. That is, the private key generator in IBE knows decryption keys for all identities and consequently can decrypt any ciphertexts. The certificate‐based encryption (CBE) scheme proposed in EUROCRYPT 2003 provides a solution for the key escrow problem by allowing the certification authority to possess a partial decryption key that comprises the full decryption key together with the user‐generated private key. In this paper, we propose new CBE schemes without pairing and prove them to be Indistinguishability under Chosen Ciphertext Attack secure in the random oracle model based on the hardness of the computational Diffie–Hellman problem. When compared with other CBE schemes, our schemes are significantly efficient in terms of performance, which makes our schemes suitable for computation‐limited node (e.g., sensor, wearable device) networks. Copyright © 2016 John Wiley & Sons, Ltd.

Predicate encryption is a public-key encryption that supports attribute-hiding as well as payload-hiding and achieves high flexibility in terms of access control. Since Katz, Sahai, and Waters first proposed the predicate encryption scheme in 2008, several predicate encryption schemes have been published. Unfortunately these are impractical as they require$O(n)$pairing computations for decryption with considerably large sized public parameters, secret key, and ciphertext, where$n$is the dimension of the attribute/predicate vectors. In this paper, we propose a very efficient predicate encryption scheme that requires only$n$exponentiation plusthreepairing computations for decryption with shorter sized public parameters, secret key, and ciphertext. The proposed scheme is proven selective attribute-secure against chosen-plaintext attacks in the standard model under the Asymmetric Decisional Bilinear Diffie-Hellman assumptions.

Abstract Predicate encryption (PE) that provides both the access control of ciphertexts and the privacy of ciphertexts is a new paradigm of public‐key encryption. An important application of PE is a searchable encryption system in cloud storage, where it enables a client to securely outsource the search of a keyword on encrypted data without revealing the keyword to the cloud server. One practical issue of PE is to devise an efficient revocation method to revoke a user when the secret key of the user is compromised. Privacy preserving revocable PE (RPE) can provide not only revocation but also the privacy of revoked users. In this paper, we first define two new security models of privacy preserving RPE: the strongly full‐hiding (FH) security and the weakly FH security. Next, we propose a general RPE construction from any PE scheme and prove its security in the weakly FH security model. Our generic RPE scheme is efficient because the number of ciphertext elements is not proportional to the number of users in a receiver set. Additionally, our RPE scheme can support polynomial‐size circuits if a recently proposed functional encryption scheme for polynomial‐size circuits is used as an underlying PE scheme. Copyright © 2014 John Wiley & Sons, Ltd.

The pyroprocessing operation-modelling is characterized as complicated batch type operation and tangled material flow logic, and handling many numbers of chemical elements. Discrete event system modeling was performed to build an integrated operation model, a simulation of which showed that a dynamic material flow was implemented. All data related to a dynamic material flow were recorded in database tables, and used for verification and validation in terms of material balance. Compared to equilibrium material balance, dynamic mass balance showed that the amount of material transported upstream and downstream in the unit process satisfied the mass balance equation at every batch operation. This study also showed that a dynamic material flow, which is a basic framework for an integrated pyroprocessing simulator, was well working. The integrated model built thus far will be improved in a few years toward an integrated simulator with safeguards assessment, technical feasibility, and economic feasibility modules.

ABSTRACT Most of broadcast encryption schemes do not provide source authentication property. This allows an adversary to launch impersonating attacks. Therefore, broadcast encryption scheme without source authentication is not applicable in our real life as it is. In this paper, we propose two source‐authenticated broadcast encryption schemes that achieve both confidentiality and authenticity simultaneously. Ciphertexts in both schemes are of constant size, independent of the size of the receiver set. The first scheme is particularly efficient in case of pre‐computation, whereas the overall performance of the second scheme is better than that of Selvi et al.'s scheme. Copyright © 2013 John Wiley & Sons, Ltd.