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In the era of cloud computing, public key encryption with keyword search (PEKS) is an extremely useful cryptographic tool for searching on encryption data, whose strongest security notion is indistinguishability encryption against chosen ciphertext attack (ind-cca). Adballa et al. presented a transformation from identity based encryption (IBE) to PEKS in the Theory of Cryptography Conference 2010. This paper proposes a new framework of ind-cca secure PEKS in the standard model. Our main technical tool is a newly introduced notion of smooth projective hash function with key mapping, in which the hash key hk is mapped into another mapping projection key mhp besides the classical projection key hp. Finally, we provide an instantiation of our framework based on symmetric eXternal Diffie–Hellman assumption. [ABSTRACT FROM AUTHOR]

Functional encryption (FE) can implement fine-grained control to encrypted plaintext via permitting users to compute only some specified functions on the encrypted plaintext using private keys with respect to those functions. Recently, many FEs were put forward; nonetheless, most of them cannot resist chosen-ciphertext attacks (CCAs), especially for those in the secret-key settings. This changed with the work, i.e., a generic transformation of public-key functional encryption (PK-FE) from chosen-plaintext (CPA) to chosen-ciphertext (CCA), where the underlying schemes are required to have some special properties such as restricted delegation or verifiability features. However, examples for such underlying schemes with these features have not been found so far. Later, a CCA-secure functional encryption from projective hash functions was proposed, but their scheme only applies to inner product functions. To construct such a scheme, some nontrivial techniques will be needed. Our key contribution in this work is to propose CCA-secure functional encryptions in the PKE and SK environment, respectively. In the existing generic transformation from (adaptively) simulation-based CPA- (SIM-CPA-) secure ones for deterministic functions to (adaptively) simulation-based CCA- (SIM-CCA-) secure ones for randomized functions, whether the schemes were directly applied to CCA settings for deterministic functions is not implied. We give an affirmative answer and derive a SIM-CCA-secure scheme for deterministic functions by making some modifications on it. Again, based on this derived scheme, we also propose an (adaptively) indistinguishable CCA- (IND-CCA-) secure SK-FE for deterministic functions. The final results show that our scheme can be instantiated under both nonstandard assumptions (e.g., hard problems on multilinear maps and indistinguishability obfuscation (IO)) and under standard assumptions (e.g., DDH, RSA, LWE, and LPN). [ABSTRACT FROM AUTHOR]

The Snowden incident shows that powerful attackers can compromise users' machines to steal users' private information. Currently, many encryption schemes that have proven to be secure cannot detect vulnerabilities. These vulnerabilities may reveal users' secrets, e.g., a machine hides some backdoors without a user's awareness, and an attacker can steal the user's private information through these backdoors. In 2015, Mironov and Stephens-Davidowitz proposed a new framework for solving this problem: cryptographic reverse firewall (CRF). However, their protocols can't protect certificateless public key encryption (CL-PKE). In this paper, we design a CRF protocol for CL-PKE, which is a one-round CL-PKE with CRFs (CL-PKE-CRF) deployed on a receiver and a key generating centre (KGC). This protocol is proved to achieve indistinguishability against chosen plaintext attack (IND-CPA). Compared with existing protocol with CRFs and two CL-PKE schemes, our protocol has the least communication cost. Meanwhile, we use JPBC library to implement our one-round CL-PKE-CRF. The experimental results indicate that under high security levels, our protocol has a advantage in the percentage of the running time. Since our protocol can resist exfiltration attacks from internal attackers, it is efficient and practical. Finally, we apply the same method to design a secure and effective one-round certificateless public key signature with a CRF (CL-PKS-CRF). This means that our protocol is not only targeted at a single CL-PKE scheme, but also can inspire the design of other certificateless public key cryptography schemes with CRFs. [ABSTRACT FROM AUTHOR]