Abstract Public key encryption scheme with keyword search is a promising technique supporting search on encrypted data without leaking any information about the keyword. In real applications, it’s critical to find an effective revocation method to revoke users in multi-user cryptosystems, when user’s secret keys are exposed. In this paper, we propose the first designated server-aided revocable identity-based encryption scheme with keyword search (dSR-IBKS) from lattice. The dSR-IBKS model requires each user to keep just one private key corresponding with his identity and does not need to communicate with the key generation center or the server during key updating. We have proved that our scheme can achieve chosen keyword indistinguishability in the standard model. In particular, our scheme can designate a unique tester to test and return the search results, therefore no other entity can guess the keyword embedded in the ciphertext by generating search queries and doing the test by itself. We provide a formal security proof of our scheme assuming the hardness of the learning with errors problem on the standard model.
Abstract Public key encryption scheme with keyword search is a promising technique supporting search on encrypted data without leaking any information about the keyword. In real applications, it’s critical to find an effective revocation method to revoke users in multi-user cryptosystems, when user’s secret keys are exposed. In this paper, we propose the first designated server-aided revocable identity-based encryption scheme with keyword search (dSR-IBKS) from lattice. The dSR-IBKS model requires each user to keep just one private key corresponding with his identity and does not need to communicate with the key generation center or the server during key updating. We have proved that our scheme can achieve chosen keyword indistinguishability in the standard model. In particular, our scheme can designate a unique tester to test and return the search results, therefore no other entity can guess the keyword embedded in the ciphertext by generating search queries and doing the test by itself. We provide a formal security proof of our scheme assuming the hardness of the learning with errors problem on the standard model.
Public key encryption scheme with keyword search (PEKS) enables us to search the encrypted data in a cloud server with a keyword, and no one can obtain any information about the encrypted data without the trapdoor corresponding to the keyword. The PEKS is useful to keep the management of large data storages secure such as those in a cloud. In this paper, to protect against quantum computer attacks, we present a lattice-based identity-based encryption scheme with keyword search. We have proved that our scheme can achieve ciphertext indistinguishability in the random oracle model, and our scheme can also achieve trapdoor security. In particular, our scheme can designate a unique tester to test and return the search results, therefore it does not need a secure channel. To the best of our knowledge, our scheme is the first identity- based encryption scheme with keyword search from lattice assumption.
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.
In the last decade, lattices have become one of the most powerful tools in constructing cryptographic schemes, which enjoy conjectured resistance against quantum computers and strong security guarantees from worst-case to average-case reductions, as well as asymptotic efficiency. For a multi-user cryptosystem, user revocation has been a necessary but challenging problem. However, all known revocable schemes are either based on number-theoretic assumptions or lattice-based but less efficient compared to the art-of-date systems. In this thesis, we focus on investigating user revocation model and the associated lattice-based instantiations. Our constructions have two goals: (i) to improve the existing revocable lattice-based cryptosystems in terms of efficiency and security; (ii) to consider the revocation functionality in new contexts from lattices. For the former, we carefully adapt the very recent revocation model into the lattice setting. The latter can be achieved either by using the existing revocation models (without concrete constructions from lattices) or by proposing new revocation models. We construct a series of cryptosystems supporting efficient revocations as follows. A revocable identity-based encryption (IBE) scheme, which is more efficient than all existing such schemes from lattices. We follow the architecture of the server-aided revocable encryptions, proposed by Qin et al. (ESORICS 2015). This paradigm provides significant efficiency advantages over previous revocation techniques in the setting of IBE. In the server-aided revocation model, most of the workloads on the user side are outsourced to an untrusted server, which can be untrusted since it does not possess any private information. With the help of this server, non-revoked users do not need to update anything when the system revokes other users. We equip Agrawal, Boneh, and Boyen's IBE (EUROCRYPT 2010) with the server-aided revocation method. In the technical view, we observe that a ``double encryption'' mechanism is well-suited in such a server-aided system. We also show that our scheme is provably secure provided with the strong hardness of the Learning With Errors (LWE) problem. A revocation model called server-aided revocable predicate encryption (SR-PE) and an instantiation from lattices. We consider the server-aided revocation mechanism in the predicate encryption (PE) setting and formalize the notion of SR-PE with rigorous definitions and security model. Moreover, we introduce a construction of SR-PE for the scheme introduced by Agrawal, Freeman, and Vaikuntanathan (ASIACRYPT 2011) and prove that our scheme is selectively secure in the standard model. The correctness of our scheme relies on a special property of lattice-based encryption schemes. A lattice-based construction of predicate encryption following the direct revocation mechanism. In such a mechanism, it forces the ciphertexts to carry on the revocation information. Nieto, Manulis, and Sun (ACISP 2012) considered direct revocations in the PE setting and suggested the notion of full-hiding security for revocable PE schemes, which demands that the encrypted data keeps the privacy of not only the plaintext and the associated attribute, but also the revocation information. Following their pairing-based construction, we introduce a corresponding instantiation from lattice assumptions. Regarding efficiency, our lattice-based scheme is somewhat comparable to the construction by Nieto, Manulis, and Sun. Our scheme achieves the full-hiding security thanks to the anonymity of one IBE instance we additionally introduce into the system.
To ensure the privacy and security of the stored data, the data can be encrypted first and then stored on the cloud. However, it faces the problem that users cannot search keywords in a large amount of data, which limits the flexibility of file sharing in the cloud environment. Searchable encryption can effectively support users to retrieve encrypted data in the cloud. Public key searchable encryption (PEKS) is used to retrieve the target encrypted data by searching specific keywords. However, the development of quantum computers has led to attacks on conventional encryption algorithms, and it is necessary to design searchable encryption schemes that can resist quantum attacks. Therefore, we propose a lattice puncturable PEKS scheme. Besides resisting quantum attacks, the proposed scheme attains efficient and flexible user revocation. Firstly, identity-based encryption is employed to minimize the complexity of key management. Secondly, the puncturable encryption technology is integrated into the proposed encryption to revoke the decryption capability for selected messages, enabling authorized recipients to repeatedly update their decryption keys to retrieve the currently encrypted messages. Finally, we prove the security of our scheme under the indistinguishability against chosen keyword attack (IND-PUN-sID-CKA), and conduct a comparison with other schemes to emphasize its advantages. Although the scheme does not have an edge in size, it holds an advantage in key update after adding the puncture function and also realizes higher security.
Abstract. In this paper, we present an identity-based encryption (IBE) scheme from lattices with efficient key revocation. We adopt multiple trapdoors from the Agrawal-Boneh-Boyen and Gentry-Peikerty-Vaikuntanathan lattice IBE schemes to realize key revocation, which in turn, makes use of binary-tree data structure. Using our scheme, key update requires logarithmic complexity in the maximal number of users and linear in the number of revoked users for the relevant key authority. We prove that our scheme is selective secure in the standard model and under the LWE assumption, which is as hard as the worst-case approximating short vectors on arbitrary lattices. Moreover, our key revocation techniques from lattices can be applied to obtain revocable functional encryption schemes in the similar setting.
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.