We introduce the basic concept, background, and development of mobile communication systems from the first generation (1G) to the fifth generation (5G) including their antenna systems. We also describe the requirements for 5G networking and optimization of antenna systems, and present the basic principle of three-dimensional array antennas. Weight optimization methods of massive multiple-input multiple-output (MIMO) antennas are proposed and verified. Finally, several ideas are given to solve the problem of power consumption of 5G antenna systems.

Transport Layer Security (TLS) is one of the most widely used Internet protocols for secure communications. TLS 1.3, the next-generation protocol, is currently under development, with the latest candidate being draft-18. For flexibility and compatibility, TLS supports various ciphersuites and offers configurable selection of multiple protocol versions, which unfortunately opens the door to practical attacks. For example, although TLS 1.3 is now proven secure separately, coexisting with previous versions may be subject to backwards compatibility attacks. In this paper, we present a formal treatment of the multi-ciphersuite and backwards-compatibility security of TLS 1.3 (specifically, draft-18). We introduce a multi-stage security model, covering all known kinds of compositional interactions (w.r.t. ciphersuites and protocol versions) and reasonably strong security notions. Then we dissect the cross-ciphersuite attack regarding TLS 1.2 in our model, and show that the TLS 1.3 handshake protocol satisfies the multi-ciphersuite security, highlighting the strict necessity of including more information in the signature. Furthermore, we demonstrate how the backwards compatibility attack by Jager et al. can be identified owing to our model, and prove that the handshake protocol can achieve our desired strong security if certain countermeasures are adopted. Our treatment is also applicable to analyzing other protocols.

We introduce MobiCeal, the first practical Plausibly Deniable Encryption (PDE) system for mobile devices that can defend against strong coercive multi-snapshot adversaries, who may examine the storage medium of a user's mobile device at different points of time and force the user to decrypt data. MobiCeal relies on "dummy write" to obfuscate the differences between multiple snapshots of storage medium due to existence of hidden data. By incorporating PDE in block layer, MobiCeal supports a broad deployment of any block-based file systems on mobile devices. More importantly, MobiCeal is secure against side channel attacks which pose a serious threat to existing PDE schemes. A proof of concept implementation of MobiCeal is provided on an LG Nexus 4 Android phone using Android 4.2.2. It is shown that the performance of MobiCeal is significantly better than prior PDE systems against multi-snapshot adversaries.

Wearing smartwatches becomes increasingly popular in people’s lives. This paper shows that a smartwatch can help its bearer authenticate to a login system effectively and securely even if the bearer’s password has already been revealed. This idea is motivated by our observation that a sensor-rich smartwatch is capable of tracking the wrist motions of its bearer typing a password or PIN, which can be used as an authentication factor. The major challenge in this research is that a sophisticated attacker may imitate a user’s typing behavior as shown in previous research on keystroke dynamics based user authentication. We address this challenge by applying a set of machine learning and deep learning classifiers on the user’s wrist motion data that are collected from a smartwatch worn by the user when inputting his/her password or PIN. Our solution is user-friendly since it does not require users to perform any additional actions when typing passwords or PINs other than wearing smartwatches. We conduct a user study involving 51 participants so as to evaluate the feasibility and performance of our solution. User study results show that the best classifier is the Bagged Decision Trees, which yields 4.58% FRR and 0.12% FAR on a QWERTY keyboard, and 6.13% FRR and 0.16% FAR on a numeric keypad.

Over the Internet, digital signature has been an indispensable approach to securing e-commerce and other online transactions requiring authentication. Concerning the computing costs of signature generation and verification, it has become a more and more common practice for security practitioners to outsource such computations from heavily loaded application servers called tenants to dedicated proxies like signature servers in the enterprise private cloud. In this paper, we present our high-performance signature server called Guess. It implements the elliptic curve digital signature algorithm (ECDSA) with 256-b key size on a Linux-powered commodity computer, harnessing a desktop graphics processing unit as a featured cryptographic accelerator. We demonstrate our experience in maximizing the computing power of Guess and also its capability to deliver such power to the tenants, which includes down-to-earth customization and optimization considering various hardware and software factors. Our comprehensive implementation of ECDSA is tested against intensive network traffic. Field experiments show that Guess achieves Ts= 8.71 × 106operations per second (OPS) for signature generation or Tv= 9.29 × 105OPS for verification, which is significantly faster than existent prototypes and products. Guess is a universal server that readily supports various categories of elliptic curve cryptographic schemes, such as digital signature, key agreement, and encryption.

The postMessage mechanism in HTML5 enables different webpage origins to exchange information and communicate. It becomes increasingly popular among the websites that need to import contents from third-party services, such as advertisements and preferable recommendations. Ideally, a receiver function should be locally implemented in the hosting page that needs to receive third-party messages. However, in the real world, the receiver function is usually provided by a third-party service provider, and the function code is imported via the HTML "script" tag so that the imported code is deemed as from the same origin with the hosting page. In the case that a site uses multiple third-party services, all the receiver functions imported by the hosting page can receive messages from any third-party provider. Based on this observation, we identify a new information leakage threat named DangerNeighbor attacks that allow a malicious service eavesdrop messages from other services to the hosting page.

Bolstering public key authentication of networking entities, digital certificates are an entrenched part of Internet security. A digital certificate is an electronic document signed by a certificate authority (CA), vouching that the identified subject owns the declared public key (and the corresponding private key). In general, CAs are also responsible for certificate revocation as well as reissue, and certificates by nature are considered independent of each other. In this paper, we address the problem of certificate management and propose a flexible framework to create correlated certificates. We then apply it to implement the so-called multi-certificate public key infrastructure, which supports user self services, such as certificates' spontaneous substitution as well as self-reissue after self-revocation. To the best of our knowledge, this is the first scheme for certificate users to achieve self-reissue. Another application of the proposed framework is the so-called anonymous digital certificate, which still binds a user's identity to her public key, but in an anonymous yet user-controllable manner. That is, a user can reveal her identity-key binding only to her specified communication peers, while remaining anonymous to the general public, achieving privacy as these certificates are generally unlinkable.

Public key infrastructures (PKIs) are proposed to provide various security services. Some security services such as confidentiality require key escrow in certain scenarios, whereas some others such as non‐repudiation and authentication usually prohibit key escrow. Moreover, these two conflicting requirements can coexist for one PKI user. The popular solution in which each user has two different certificates and an escrow authority backs up all escrowed private keys faces the problems of efficiency and scalability. In this study, a novel key management infrastructure called RIKE + is proposed to integrate the ‘inherent key escrow’ of identity‐based encryption (IBE) into PKIs. In RIKE+, (the hash value of) a user's PKI certificate also serves as a ‘revocable identity’ to derive the user's IBE public key, and the revocation of this IBE key pair is achieved by the certificate revocation of PKIs. Therefore the certificate binds the user with two key pairs, one of which is escrowed inherently and the other is not. Furthermore, RIKE+ employs chameleon hash to flexibly control the relationship between the certificate and the IBE key pair. In the case of certificate renewal and revocation, chameleon hash enables RIKE+ to manipulate the hash value of the new certificate, so the user's IBE key pair is not unconditionally changed unless it is necessary. RIKE+ is an effective certificate‐based solution compatible with traditional PKIs and can be built on existing X.509 PKIs.

Smartphones are playing an increasingly important role in personal life and carrying massive private data. Unfortunately, once the smartphones are stolen, all the sensitive information, such as contacts, messages, photos, credit card information and passwords, may fall into the hands of malicious people. In order to protect the private data, remote deletion mechanism is required to allow owners to wipe the sensitive data on the stolen phone remotely. Existing remote deletion techniques rely on the availability of either WiFi for Internet connection or SIM card for cellular network connection; however, these requirements may not be satisfied when the phones are stolen by some sophisticated adversaries. In this paper, we propose a new remote deletion mechanism that allows the phone owner to delete the private data remotely even if the WiFi is disabled and the SIM card is unplugged. The basic idea is to use emergency call mechanisms to establish a communication connection with a service provider to verify the state of the phone and perform remote deletion. We present a case study of our mechanism with the Universal Mobile Telecommunications System (UMTS) network.

ABSTRACT Making friends by publishing and sharing personal data in a special interest group has become popular in online social networks. Data security is a major concern, as digital content can be easily accessed from all over the Internet, and the online social network service provider is often for profit and semi‐trusted. The standard solution to data security is encryption, but sharing of encrypted data then becomes a challenging task. In this paper, employing attribute‐based encryption (ABE), we propose Masque+, a novel hierarchical and fine‐grained access control mechanism. On the basis of key policy ABE, the service provider manages users on the system level, but without being able to access their sensitive data. On the basis of ciphertext policy ABE, members of an interest group may customize their own access policies specifically. Masque+ features pragmatic functionalities like user revocation on the system level and the group level, respectively. We also build a prototype to validate the cryptographic algorithms involved in Masque+ and evaluate their performances. Real experimental data show that Masque+ incurs fairly reasonable costs even in cases where the access control policy is significantly complex. Copyright © 2013 John Wiley & Sons, Ltd.

ABSTRACT A wireless sensor network composed of a number of sensor nodes is often deployed in unattended and harsh environments to perform various monitoring tasks. Due to cost concerns, usually, sensor nodes are not made tamper‐resistant, and a captured node may be easily compromised by an adversary. With the revealed secret credentials, the adversary can create many duplicate nodes that are seemingly legitimate, and deploy them into the network to cripple the monitoring applications. Defending against node replication attacks has become an important research topic in sensor network security, but so far, not many solutions have been proposed, most of which adopt a stationary network model where sensor nodes are fixed and immobile. In this work, we address the problem of detecting node replication attacks in a mobile sensor network, where each sensor node freely and randomly roams in the sensing region all the time, and one node meets with another in an occasional and unpredictable manner. For replication attacks where the replicas do not conspire, we employ very lightweight token‐based authentication as a detection approach. In case the replicas conspire by communicating with each other in an efficient manner, we harness the random encounters between physical nodes and propose a detection method based on statistics. Compared with existent solutions, our detections have the nice feature that sensor nodes are freed from the fragile assumption that they can correctly obtain their geographic positions, and that even loose time synchronization may be unnecessary. Copyright © 2011 John Wiley & Sons, Ltd.

Recently, Zhou et al. proposed a multicast authentication protocol named MABS which employs an efficient cryptographic primitive called batch verification to authenticate an arbitrary number of data packets simultaneously. Three implementations were presented: MABS-RSA, MABS-BLS, and MABS-DSA. In this comment, we are concerned with the last implementation, which is claimed to be much more efficient than the others. Our particular interest also lies in the fact that MABS-DSA was designed to thwart a known attack against its underlying batch DSA primitive and is claimed to be with increased security. After a careful revisit of the involved arithmetic, however, we find that the real issue lies in protocol correctness rather than security; the algorithm of MABS-DSA actually does not hold as one would expect. More specifically, even if each of the data packets was signed by an honest sender and securely delivered to the receiver, verification of the batch of signatures will still almost always fail.

In an end-to-end encryption model for a wireless sensor network (WSN), the network control center preloads encryption and decryption keys to the sensor nodes and the subscribers respectively, such that a subscriber can use a mobile device in the deployment field to decrypt the sensed data encrypted by the more resource-constrained sensor nodes. This paper proposes SMS-SED, a provably secure yet practically efficient key assignment system featuring a discrete time-based access control, to better support a business model where the sensors deployer rents the WSN to customers who desires a higher flexibility beyond subscribing to strictly consecutive periods. In SMS-SED, a node or a mobile device stores a secret key of size independent of the total number of sensor nodes and time periods. We evaluated the feasibility of deploying 2000 nodes for 4096 time periods at 1024-bit of security as a case study, studied the trade off of increasing the storage requirement of a node to significantly reduce its computation time, and provided formal security argument in the random oracle model.

Abstract A cross‐realm client‐to‐client password‐authenticated key agreement (C2C‐PAKA) protocol allows network clients from different realms managed by different servers to agree on a session key in an authentic manner based on easily memorizable passwords. In this paper, we present a generic framework for constructing a cross‐realm C2C‐PAKA protocol from any secure smart card‐based password authentication (PA‐SC) protocol. The security proof of our construction can be derived from the underlying PA‐SC protocol employing the same assumptions. Our generic framework appears to be the first one with provable security. In addition, compared with similar protocols, the instantiation of our construction achieves improved efficiency. Copyright © 2010 John Wiley & Sons, Ltd.

Abstract In resource‐constrained wireless sensor networks, data aggregation is a key technique for power‐efficient information acquisition. Consequently, the intermediate sensor nodes performing aggregation tasks known as aggregators are valuable and attractive targets for attackers. We address the problem of defending against malicious adversaries who intend to stealthily change some aggregates to entice the base station to accept deceiving results. A secure and efficient aggregation scheme is proposed, in which the base station composes a secret configuration matrix and each sensor node is pre‐loaded with a limited part of the matrix known as a secret share containing certain local instructions. For each aggregation session, a set of scrambled aggregates are constructed in such a manner that there exists a secret yet unrevealed relationship between these values. The base station, aware of the relationship derived from the configuration matrix, can both extract the intended result from the received aggregates and verify it on its own. Our scheme avoids the interactive verification phase which existent protocols typically take to ensure the aggregation integrity, and thus observably lowers the communication overhead. The proposed scheme also features protection of data confidentiality, and analysis shows that it can detect stealthy alteration attacks with a significant probability. Copyright © 2010 John Wiley & Sons, Ltd.

Many sensor network applications require sensors to obtain their locations correctly. Various techniques have been proposed to locate regular sensors based on some special nodes called beacon nodes, which are supposed to know their locations. However, most of the existing techniques are vulnerable in hostile environments. The position estimation accuracy decreases drastically when some of the beacon nodes are compromised. Providing a certain degree of localization accuracy at the presence of malicious beacons becomes a very challenging task. In this paper, a secure and efficient voting-on-grid clustering (VoGC) scheme is proposed to mitigate the impact of such attacks. In our scheme, malicious beacon signals are filtered out according to the clustering result of intersections of location reference circles. We employ a voting-on-grid method instead of traditional clustering algorithms to reduce the computational cost. Simulation results demonstrate that the proposed scheme can provide very good localization accuracy and identify a high proportion of malicious beacon signals.

We address the problem of distributing a confidentially shared session key to a multimedia multicast group for content protection. In two such schemes proposed by Trappe , the session key is distributed by employing a homogenized rekey message format. We show that their rekey algorithm in itself is vulnerable to specialized collision attacks, in which even a completely passive outer adversary, who never joins the system and thus never knows any secret user keys, can still reveal the session key of the multimedia multicast with an observable probability but only involving a time complexity far lower than an exhaustive search.

We address the problem of distributing a group-oriented secret from a centralized key server to a number of privileged recipients, known as broadcast encryption. In a set of existent schemes, this common shared secret is distributed as an arithmetic remainder embedded in a broadcast keying message, such that upon receiving the message, a legitimate recipient only needs to perform one modular operation upon the keying information to derive the secret. In this article, however, we point out a generic weakness in these protocols and demonstrate efficient methods for cryptanalysis. The presented approaches follow a collision attack paradigm and can work in a manner that even a completely passive outsider may somehow acquire the secret. Numerical analysis shows that in practical scenarios, our technique can compromise the common shared secret with a significant probability, implying that these broadcast encryption schemes are highly vulnerable.

Due to limited server and network capacities, proxies are introduced for streaming applications to cache multimedia content from the media source to enable a scalable service and to improve the user experience. In this paper we first review the security aspect of a proxy encryption framework recently presented by Yeung et al. featuring the multikey RSA technique. Then addressing the performance aspect, we propose a redesigned cost-efficient architecture, which is based on a media key management mechanism substantially different from Yeung et al. 's framework and improves the overall system significantly.

Many modern network applications are based upon a multiparty communication model where participants are organized as a peer group. Especially, the communication medium in a wireless network is broadcast in nature, which facilitates group oriented applications like shared whiteboard. Given the openness of today's network, providing privacy for peer groups is a critical design issue. For example, the broadcast nature of wireless networks implies that traffic sent over the air can be easily captured. Therefore, security services like traffic encryption and key management are essential to upper layer applications. In this paper we study a multiparty key agreement protocol based on the hyperspherical equation, in which each participant fairly contributes to the final radius of a virtual hypersphere. We reveal some undesirable design points in the scheme, as well as some serious security defects. We show that the protocol is vulnerable to attacks and thus is unsuitable for practical adoption.