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Data outsourcing has become an industry trend with the popularity of cloud computing. How to search data securely and efficiently has received unprecedented attention. Dynamic Searchable Symmetric Encryption (DSSE) is an effective method to solve this problem, which supports file updates and keyword-based searches over encrypted data. Unfortunately, most existing DSSE schemes have privacy leakages during the addition and deletion phases, thus proposing the concepts of forward and backward privacy. At present, some secure DSSE schemes with forward and backward privacy have been proposed, but most of these DSSE schemes only achieve single-keyword query in the single-client setting, which seriously limits the application in practice. To solve this problem, we propose a multi-client and multi-keyword searchable symmetric encryption scheme with forward and backward privacy (MMKFB). Our scheme focuses on the multi-keyword threshold queries in the multi-client setting, which is a new pattern of multi-keyword search realized with the help of additive homomorphism. And performance analysis and experiments demonstrate that our scheme is more practical for use in small and medium size databases. Especially when a large number of files are updated at once, our scheme has advantages over some existing DSSE schemes in terms of computational efficiency and client storage overhead. [ABSTRACT FROM AUTHOR]

Puncturable encryption allows recipients to revoke the decryption capability of ciphertexts flexibly, thus provides a fine-grained way to achieve forward security. So far, puncturable encryption and its variants have found many interesting applications, including the design of advanced cryptographic protocols and messaging systems. In this paper, we put forward the first generic construction of incremental symmetric puncturable encryption that can support an arbitrary number of punctures and achieve semantic security without random oracles. To this end, we introduce the notion of extended key-homomorphic puncturable PRF (EKHP-PRF) by abstracting the properties implicitly desired in many applications of almost key-homomorphic PRFs, which essentially removes the influence of errors due to almost key-homomorphism. Moreover, we present an efficient instantiation of EKHP-PRF based on a variant of Module Learning with Errors (MLWE) problem, namely non-uniform MLWE (NMLWE). Thus, we get the first lattice-based puncturable encryption featuring an arbitrary number of punctures in the standard model. [ABSTRACT FROM AUTHOR]

The explosive growth of big data is pushing forward the paradigm of cloud-based data store today. Among other, distributed storage systems are widely adopted due to their superior performance and continuous availability. However, due to the potentially wide attacking surfaces of the public cloud, outsourcing data store inevitably raises new concerns on user privacy exposure and unauthorized data access. Besides, directly introducing a centralized third-party authority for query authorization management does not work because it still can be compromised. In this paper, we propose a blockchain-assisted framework that can support trustworthy data sharing services. In particular, data owners allow to outsource their sensitive data to distributed systems in encrypted form. By leveraging smart contracts of blockchain, a data owner can distribute secret keys for authorized users without extra round interaction to generate the permitted search tokens. Meanwhile, such blockchain-assisted framework naturally solves the trust issues of query authorization. Besides, we devise a secure local index framework to support encrypted keyword search with forward privacy and mitigate blockchain overhead. To validate our design, we implement the prototype and deploy it at Amazon Cloud. Extensive experiments demonstrate the security, efficiency, and effectiveness of the blockchain-assisted design. [ABSTRACT FROM AUTHOR]

The TLS 1.3 0-RTT mode enables a client reconnecting to a server to send encrypted application-layer data in “0-RTT” (“zero round-trip time”), without the need for a prior interactive handshake. This fundamentally requires the server to reconstruct the previous session’s encryption secrets upon receipt of the client’s first message. The standard techniques to achieve this are session caches or, alternatively, session tickets. The former provides forward security and resistance against replay attacks, but requires a large amount of server-side storage. The latter requires negligible storage, but provides no forward security and is known to be vulnerable to replay attacks. In this paper, we first formally define session resumption protocols as an abstract perspective on mechanisms like session caches and session tickets. We give a new generic construction that provably provides forward security and replay resilience, based on puncturable pseudorandom functions (PPRFs). We show that our construction can immediately be used in TLS 1.3 0-RTT and deployed unilaterally by servers, without requiring any changes to clients or the protocol. To this end, we present a generic composition of our new construction with TLS 1.3 and prove its security. This yields the first construction that achieves forward security for all messages, including the 0-RTT data. We then describe two new constructions of PPRFs, which are particularly suitable for use for forward-secure and replay-resilient session resumption in TLS 1.3. The first construction is based on the strong RSA assumption. Compared to standard session caches, for “128-bit security” it reduces the required server storage by a factor of almost 20, when instantiated in a way such that key derivation and puncturing together are cheaper on average than one full exponentiation in an RSA group. Hence, a 1 GB session cache can be replaced with only about 51 MBs of storage, which significantly reduces the amount of secure memory required. For larger security parameters or in exchange for more expensive computations, even larger storage reductions are achieved. The second construction combines a standard binary tree PPRF with a new “domain extension” technique. For a reasonable choice of parameters, this reduces the required storage by a factor of up to 5 compared to a standard session cache. It employs only symmetric cryptography, is suitable for high-traffic scenarios, and can serve thousands of tickets per second. [ABSTRACT FROM AUTHOR]

Order-preserving encryption (OPE) and order-revealing encryption (ORE) are among the core ingredients for encrypted databases (EDBs). In this work, we study the leakage of OPE and ORE and their forward security. We propose generic yet powerful file-injection attacks (FIAs) on OPE/ORE, aimed at the situations of possessing order by and range queries. Our FIAs only exploit the ideal leakage of OPE/ORE (in particular, no need of data denseness or frequency). We also improve their efficiency with the frequency statistics using a hierarchical idea such that the high-frequency values will be recovered more quickly. We conduct some experiments on real datasets to test the performance, and the results show that our FIAs can cause an extreme hazard on most of the existing OPEs and OREs with high efficiency and 100% recovery rate. We then formulate forward security of ORE, and propose a practical compilation framework for achieving forward secure ORE to resist the perniciousness of FIA. The compilation framework can transform most of the existing OPEs/OREs into forward secure OREs, with the goal of minimizing the extra burden incurred on computation and storage. We also present its security proof, and execute some experiments to analyze its performance. The proposed compilation is highly efficient and forward secure. [ABSTRACT FROM AUTHOR]

The three-party (two clients and one server) authenticated key exchange protocols use a pre-shared password to authenticate each other, and then by the help of server to make the two clients compute a novel session key. At present, the situation of this application is very different from those considered in the conventional literatures, and the biggest two differences are that most of the former literatures cannot guarantee the user anonymity and forward anonymity. Therefore, we propose a new three-party key exchange protocol based on dynamic identity authentication with forward anonymity, so that if the server's long-term key is compromised, user anonymity cannot be broken or the identities of the users cannot be traced, and both sides of the communication with the help of the authentication server can be mutual authentication and the establishment of a session key. Compared with the three-party key exchange protocols, our protocol is more effective in computing cost and communication cost for more suitable towards resource-constrained environment. [ABSTRACT FROM AUTHOR]

In this paper, we revisit the security of factoring-based signature schemes built via the Fiat-Shamir transform and show that they can admit tighter reductions to certain decisional complexity assumptions such as the quadratic-residuosity, the high-residuosity, and the ϕ-hiding assumptions. We do so by proving that the underlying identification schemes used in these schemes are a particular case of the lossy identification notion introduced by Abdalla et al. at Eurocrypt 2012. Next, we show how to extend these results to the forward-security setting based on ideas from the Itkis-Reyzin forward-secure signature scheme. Unlike the original Itkis-Reyzin scheme, our construction can be instantiated under different decisional complexity assumptions and has a much tighter security reduction. Moreover, we also show that the tighter security reductions provided by our proof methodology can result in concrete efficiency gains in practice, both in the standard and forward-security setting, as long as the use of stronger security assumptions is deemed acceptable. Finally, we investigate the design of forward-secure signature schemes whose security reductions are fully tight. [ABSTRACT FROM AUTHOR]

In recent years, the rapid development of computer science and technology brings health care into the information era. As a typical representation, wireless body area networks (WBANs) has also promoted the development of medical technology into a higher field. However, collecting data from users seriously affects personal privacy and security, that WBANs needs to overcome. In order to resolve the flaws of the existing secure authentication protocols in WBANs, we propose a lightweight implicit authentication protocol based on the Elliptic Curve Qu-Vantone (ECQV) algorithm. Moreover, we take advantage of the bidirectional key chain to design a group key management protocol between the personal digital assistance (PDA) and each of cluster head sensor nodes. The security and performance analysis show that our protocol can be performed with perfect forward security and backward security in data communication. In addition, the experimental simulation and theoretic analysis show that our protocol is more suitable for WBANs. [ABSTRACT FROM AUTHOR]

Unlike the traditional medical system, telecare medicine information system (TMIS) ensures that patients can get health-care services via the Internet at home. Authenticated key agreement protocol is very important for protecting the security in TMIS. Recently scholars have proposed a lot of authenticated key agreement protocols. In 2016, Chiou et al. demonstrated that Chen et al.'s authentication scheme fails to provide user's anonymity and message authentication and then proposed an enhanced scheme (Chiou et al., J. Med. Syst. 40(4):1-15, 2006) to overcome these drawbacks. In this paper, we demonstrate that Chiou et al.'s scheme is defenseless against key compromise impersonation (KCI) attack and also fails to provide forward security. Moreover, we propose a novel authentication scheme namely ICASME to overcome the mentioned weaknesses in this paper. Security analyses show that ICASME achieves the forward security and KCI attack resistance. In addition, it is proved that the time taken to implement the ICASME is not intolerable compared to the original protocol. [ABSTRACT FROM AUTHOR]

Recently, Wang et al. (J Secur Commun Netw 5(12):1363-1374, 2012) proposed a self-healing group key distribution (SGKD) scheme for resource-constrained wireless networks. They claimed that their proposed SGKD scheme satisfies forward security, backward security and can resist collusion attack. Unfortunately, we found some security flaws in their scheme. In this paper, we present a method to attack this scheme. The attack illustrates that this scheme does not satisfy forward security, which also directly breaks the collusion resistance capability. We also propose an improved scheme with constant storage overhead and satisfactory security. [ABSTRACT FROM AUTHOR]

Forward-secure signatures are proposed to diminish the damage of key exposure, in which the security of signatures prior to the period of key exposure can be kept. Identity-based signatures can reduce the complexity and the cost for managing the public key because the public key is replaced by any known information of a user's identity. In this paper, we discuss a new issue related to integrating forward-secure and identity-based primitives into standard applications of personal network communication security such as pretty good privacy suite and secure/multipurpose internet mail extensions in which the secret key is additionally protected by an extra secret that is possibly derived from a password. One major contribution of this paper is to construct the first forward-secure identity-based signature scheme in untrusted update environments. In this scheme, the public key can be derived from some arbitrary identification value such as an email address or a phone number, and the signing key is additionally shielded by a second factor derived from a user's password. Key update can be completed by the encrypted version of signing keys. The second factor is only needed when the signatures are produced. In addition, we give the definitions of forward security and update security in this kind of signature. At last, formal proofs of forward security and update security in the random oracle model are provided under the CDH assumption. [ABSTRACT FROM AUTHOR]

Steinwandt and Corona proposed a forward-secure identity-based non-interactive key distribution (ID-NIKD) scheme and proved its security, and then a forward-secure identity-based encryption (IBE) constructed from their forward-secure ID-NIKD scheme. In this study, attacks are presented to point out that their ID-NIKD scheme and IBE scheme are not forward-secure. We conclude that how to construct a forward-secure ID-NIKD scheme is still an open problem. [ABSTRACT FROM AUTHOR]

The key exposure problem is a practical threat for many security applications. In wireless sensor networks (WSNs), keys could be compromised easily due to its limited hardware protections. A secure group key management scheme is responsible for secure distributing group keys among valid nodes of the group. Based on the key-insulated encryption (KIE), we propose a group key management scheme (KIE-GKMS), which integrates the pair-wise key pre-distribution for WSN. The KIE-GKMS scheme updates group keys dynamically when adding or removing nodes. Moreover, the security analysis proves that the KIE-GKMS scheme not only obtains the semantic security, but also provides the forward and backward security. Finally, the theoretical analysis shows that the KIE-GKMS scheme has constant performance on both communication and storage costs in sensor nodes. [ABSTRACT FROM AUTHOR]

Identity-based non-interactive key distribution ( ID-NIKD) is a cryptographic primitive that enables two users to establish a common secret key without exchanging messages. All users of the system have access to public system parameters and a private key, obtained through the help of a trusted key generation center. In this contribution, we discuss how to capture an intuitive form of forward security for ID-NIKD schemes in a security model. Building on results of Sakai et al. as well as of Paterson and Srinivasan, we discuss how the proposed notion of forward security can be achieved in the random oracle model, using a Bilinear Diffie-Hellman assumption in combination with a forward-secure pseudorandom bit generator. We also show how a forward-secure ID-NIKD scheme can be used to realize forward-secure identity-based encryption. [ABSTRACT FROM AUTHOR]

In 2010, Hwang, et al. proposed a 'DoS-resistant ID-based password authentication scheme using smart cards' as an improvement of Kim-Lee-Yoo's 'ID-based password authentication scheme'. In this paper, we cryptanalyze Hwang, et al.'s scheme and point out that the revealed session key could threat the security of the scheme. We demonstrate that extracting information from smart cards is equal to knowing the session key. Thus known session key attacks are also effective under the assumption that the adversary could obtain the information stored in the smart cards. We proposed an improved scheme with security analysis to remedy the weaknesses of Hwang, et al.'s scheme. The new scheme does not only keep all the merits of the original, but also provides several additional phases to improve the flexibility. Finally, the improved scheme is more secure, efficient, practical, and convenient, because elliptic curve cryptosystem is introduced, the expensive smart cards and synchronized clock system are replaced by mobile devices and nonces. [ABSTRACT FROM AUTHOR]

There are many constraints in the use of digital signatures. This paper proposes a new way of using digital signatures with some restrictions, i.e. set signatures. It works in such a way that when the signing algorithm is given, one can use it to create a valid signature on a message if and only if the message belongs to a pre-defined set, and given the information about the signing algorithm, it is computationally infeasible to create valid signatures on any other arbitrary messages outside of the set. This special property enables the signing algorithm to be made public, which seems to contradict with the traditional signature where a private key is needed, which must be kept secret. What makes the problem challenging is that the signing algorithm does not reveal the secret signing key, and hence forging normal signatures for arbitrary messages is computationally infeasible. In many cases, the signing algorithm does not reveal the elements in the authorized set. As an application of the new concept, set signatures for intelligent mobile agents committing “smaller than” condition is studied, which shows the applicability of set signatures on small sets. [ABSTRACT FROM AUTHOR]

Rapid distribution of newly released confidential information is often impeded by network traffic jams, especially when the confidential information is either crucial or highly prized. This is the case for stock market values, blind auction bidding amounts, many large corporations'strategic business plans, certain news agencies'timed publications, and some licensed software updates. Hierarchical time-based information release (HTIR) schemes enable the gradual distribution of encrypted confidential information to large, distributed, (potentially) hierarchically structured user communities, and the subsequent publication of corresponding short decryption keys, at a predetermined time, so that users can rapidly access the confidential information. This paper presents and analyzes the efficiency of a novel HTIR scheme. [ABSTRACT FROM AUTHOR]

The article comments on the papers selected from the proceedings of the Eighth International Information Security Conference from September 20 to September 23,2005 in Singapore. The paper "Execution Transactions for Defending Against Software Failures” by Stelios Sidiroglou and Angelos Keromytis examines the problem of containing buffer overflow attacks in a safe and efficient manner.