Blockchain is a technology of recording ledgers in a distributed manner. It uses a consensus mechanism, digital signature and hash chains to realize the reliable storage of ledgers, and provide services such as traceability, integrity and no-repudiation for transactions in ledgers in a decentralized way. These services make blockchain have great application potentiality in the fields of healthcare, Fintech, computational law and so on. Before wide spreading its applications, blockchain must solve problems such as efficiency and privacy. Among these problems the privacy is an important one. Because blocks on blockchain are open, when transactions in blocks involve privacy data, these data can be leaked. Thus, certain security mechanisms must be built to protect privacy data. The core of these mechanisms is the appropriate key management schemes. However, blockchain is a developing technology, and few studies have been done on key management schemes for it. Because healthcare is a big application scenario of blockchain, in this paper, according to the features of health blockchain, we use body sensor network to design a lightweight backup and efficient recovery scheme for keys of health blockchain. Analyses show that the scheme has high security and performance, and it can be used to protect privacy messages on health blockchain effectively and to promote the application of health blockchain.
The main purpose of Password-Authenticated Key Exchange (PAKE) is to allow secure authenticated communication over insecure networks between two or more parties who only share a low-entropy password. It is common practice that the secret key derived from a PAKE execution is used to authenticate and encrypt some data payload using symmetric key protocols. Unfortunately, most PAKEs of practical interest, including three protocols considered in this thesis, are studied using so-called game-based models, which -- unlike simulation models -- do not guarantee secure composition per se. However, Brzuska et al. (CCS 2011) have shown that a middle ground is possible in the case of authenticated key exchange that relies on Public-Key Infrastructure (PKI): the game-based models do provide secure composition guarantees when the class of higher-level applications is restricted to symmetric-key protocols. The question that we pose in this thesis is whether or not a similar result can be exhibited for PAKE. Our work answers this question positively. More specifically, we show that PAKE protocols secure according to the game-based Real-or-Random (RoR) definition of Abdalla et al. (PKC 2005) allow for automatic, secure composition with arbitrary, higher-level symmetric key protocols. Since there is evidence that most PAKEs secure in the Find-then-Guess (FtG) model of Bellare et al. (EUROCRYPT 2000) are in fact secure according to the RoR definition, we can conclude that nearly all provably secure PAKEs enjoy a certain degree of composition, one that at least covers the case of implementing secure channels. Although many different protocols that accomplish PAKE have been proposed over last two decades, only a few newcomers managed to find their way to real world applications - albeit lacking an intense and prolonged public scrutiny. As a step in the direction of providing one, this dissertation considers the security and efficiency of two relatively recently proposed PAKE protocols - Dragonfly and J-PAKE. In particular, we prove the security of a very close variant of Dragonfly employing the standard FtG model which incorporates forward secrecy. Thus, our work confirms that Dragonfly's main flows are sound. Furthermore, we contribute to the discussion by proposing and examining (in the RoR model of security) two variants of J-PAKE - which we call RO-J-PAKE and CRS-J-PAKE - that each makes the use of two less zero-knowledge proofs than the original protocol, at the cost of an additional security assumption. Our work reveals that CRS-J-PAKE has an edge in terms of efficiency over J-PAKE for both standard group choices: subgroups of finite fields and elliptic curves. The same is true for RO-J-PAKE, but only when instantiated with elliptic curves.
Aiming for strong security assurance, recently there has been an increasing interest in formal verification of cryptographic constructions. This paper presents a mechanised formal verification of the popular Pedersen commitment protocol, proving its security properties of correctness, perfect hiding, and computational binding. To formally verify the protocol, we extended the theory of EasyCrypt, a framework which allows for reasoning in the computational model, to support the discrete logarithm and an abstraction of commitment protocols. Commitments are building blocks of many cryptographic constructions, for example, verifiable secret sharing, zero-knowledge proofs, and e-voting. Our work paves the way for the verification of those more complex constructions.
Blockchains and other public ledger structures promise a new way to create globally consistent event logs and other records. We make use of this consistency property to detect and prevent man-in-the-middle attacks in a key exchange such as Diffie-Hellman or ECDH. Essentially, the MitM attack creates an inconsistency in the world views of the two honest parties, and they can detect it with the help of the ledger. Thus, there is no need for prior knowledge or trusted third parties apart from the distributed ledger. To prevent impersonation attacks, we require user interaction. It appears that, in some applications, the required user interaction is reduced in comparison to other user-assisted key-exchange protocols.
Luuc Van Der Horst, Kim‐Kwang Raymond Choo, Nhien‐An Le‐Khac
Bitcoin cryptocurrency is reportedly one widely used digital currency in criminal activities (e.g. used for online purchases of illicit drugs and paying of ransom in ransomware cases). However, there has been limited forensic research of bitcoin clients in the literature. In this paper, the process memory of two popular bitcoin clients, bitcoin Core and electrum, is examined with the aims of identifying potential sources and types of potential relevant data (e.g. bitcoin keys, transaction data and passphrases). Artefacts obtained from the process memory are also studied with other artefacts obtained from the client device (application files on disk and memory-mapped files and registry keys). Findings from this study suggest that both bitcoin Core and electrum's process memory is a valuable source of evidence, and many of the artefacts found in process memory are also available from the application and wallet files on the client device (disk).
Kentaroh Toyoda, P. Takis Mathiopoulos, Iwao Sasase, Tomoaki Ohtsuki
For more than a decade now, radio frequency identification (RFID) technology has been quite effective in providing anti-counterfeits measures in the supply chain. However, the genuineness of RFID tags cannot be guaranteed in the post supply chain, since these tags can be rather easily cloned in the public space. In this paper, we propose a novel product ownership management system (POMS) of RFID-attached products for anti-counterfeits that can be used in the post supply chain. For this purpose, we leverage the idea of Bitcoin's blockchain that anyone can check the proof of possession of balance. With the proposed POMS, a customer can reject the purchase of counterfeits even with genuine RFID tag information, if the seller does not possess their ownership. We have implemented a proof-of-concept experimental system employing a blockchain-based decentralized application platform, Ethereum, and evaluated its cost performance. Results have shown that, typically, the cost of managing the ownership of a product with up to six transfers is less than U.S. $1.
Lexus Jun Hong Sim, Shu Qin Ren, Sye Loong Keoh, Khin Mi Mi Aung
There is a significant increase in the amount of data breaches in corporate servers in the cloud environments. This includes username and password compromise in the cloud and account hijacking, thus leading to severe vulnerabilities of the cloud service provisioning. Traditional authentication schemes rely on the users to use their credentials to gain access to cloud service. However once the credential is compromised, the attacker will gain access to the cloud service easily. This paper proposes a novel scheme that does not require the user to present his credentials, and yet is able to prove ownership of access to the cloud service using a variant of zero-knowledge proof. A challenge-response protocol is devised to authenticate the user, requiring the user to compute a one-time pad (OTP) to authenticate himself to the server without revealing password to the server. A prototype has been implemented to facilitate the authentication of the user when accessing Dropbox, and the experiment results showed that the overhead incurred is insignificant.
Recently, Wi-Fi hotspots are installed at several places. However most communications are not encrypted and the illegal can use it maliciously, therefore effective breakthrough are required. We propose a solution of these problems using a new method derived from Bitcoin. This method uses Blockchain and logs of user access are saved to it. The administrators can identify illegal person and collect user's statistics. Bitcoin address can be used as encryption keys for communications. The Blockchain also provides a platform of regional applications. Furthermore, systems can cooperate with others at different places.
With rapid developments of sensor, wireless and mobile communication technologies, Mobile Healthcare Social Networks (MHSNs) have emerged as a popular means of communication in healthcare services. Within MHSNs, patients can use their mobile devices to securely share their experiences, broaden their understanding of the illness or symptoms, form a supportive network, and transmit information (e.g., state of health and new symptoms) between users and other stake holders (e.g., medical center). Despite the benefits afforded by MHSNs, there are underlying security and privacy issues (e.g., due to the transmission of messages via a wireless channel). The handshake scheme is an important cryptographic mechanism, which can provide secure communication in MHSNs (e.g., anonymity and mutual authentication between users, such as patients). In this paper, we present a new framework for the handshake scheme in MHSNs, which is based on hierarchical identity-based cryptography. We then construct an efficient Cross-Domain HandShake (CDHS) scheme that allows symptoms-matching within MHSNs. For example, using the proposed CDHS scheme, two patients registered with different healthcare centers can achieve mutual authentication and generate a session key for future secure communications. We then prove the security of the scheme, and a comparative summary demonstrates that the proposed CDHS scheme requires fewer computation and lower communication costs. We also implement the proposed CDHS scheme and three related schemes in a proof of concept Android app to demonstrate utility of the scheme. Findings from the evaluations demonstrate that the proposed CDHS scheme achieves a reduction of 18.14 and 5.41 percent in computation cost and communication cost, in comparison to three other related handshake schemes.
Shayan Eskandari, Jeremy Clark, Abdelwahab Hamou-Lhadj
In this paper we discuss existing approaches for Bitcoin payments, as suitable for a small business for small-value transactions. We develop an evaluation framework utilizing security, usability, deployability criteria,, examine several existing systems, tools. Following a requirements engineering approach, we designed, implemented a new Point of Sale (PoS) system that satisfies an optimal set of criteria within our evaluation framework. Our open source system, Aunja PoS, has been deployed in a real world cafe since October 2014.
Katina Michael interviews Amal Graafstra [1] about his forthcoming initiative MyUki.com (pronounced /yoo kee/) (Figure 1). UKI is an implantable near-field communication (NFC) platform for identity, security, cryptography, and payment applications. Graafstra is the entrepreneur who started Dangerous Things. com in 2013 (Figure 2), and, in this interview, he speaks on the changes he has witnessed since the Maker Revolution. Graafstra believes it is time to move ahead with products and services that can be consumed by the general population, not just members of the tech community. He observes the shortcomings of our online identities that are owned by companies and not individuals and is proposing a way to integrate biological identity using an embedded implant that will give the user greater control over all of his or her transactions. While UKI is mostly about security, cryptography, and bitcoin transactions, Graafstra is also looking at various ways his product might be used, everything from access control, transit ticketing, e-payments, and privacy applications [2].
Zero-knowledge proof is a protocol which does not reveal the any user information or secret during the authentication process. In this paper an efficient yet secure approach is proposed which could be used to for authenticating any user by using Digital Signature Algorithm and NXP security engine without exposing any of the user's secret information on the network.
Juan José Echevarria, Jon Legarda, Janire Larrañaga, Jonathan Ruiz-de-Garibay
Device-to-Device (D2D) communication enables devices in proximity to establish a wireless direct link. However, these devices may be severely constrained in terms of memory, CPU, and processing resources. Hence, a D2D communication with a constrained device implies new challenges as it does not have the resources required to be secured with standard cryptography. We propose lwAKE for class 0 devices (RFC 7228), which uses one-way cryptographic functions and zero-knowledge proofs to provide mutual authentication and a secure key establishment. We specify the protocol using the High Level Protocol Specification Language and then verify the security properties using the model checkers OFMC and CL-AtSe. The significance of the protocol stands in a key reuse for any successive authentication. Experimental results show that this shortened authentication mode reduces the computational load greatly.
Stanisław Jarecki, Aggelos Kiayias, Hugo Krawczyk, Jiayu Xu
PPSS is a central primitive introduced by Bagherzandi et al. [2] which allows a user to store a secret among n servers such that the user can later reconstruct the secret with the sole possession of a single password by contacting t + 1 (t <; n) servers. At the same time, an attacker breaking into t of these servers - and controlling all communication channels - learns nothing about the secret (or the password). Thus, PPSS schemes are ideal for on-line storing of valuable secrets when retrieval solely relies on a memorizable password. We show the most efficient Password-Protected Secret Sharing (PPSS) to date (and its implied Threshold-PAKE scheme), which is optimal in round communication as in Jarecki et al. [10] but which improves computation and communication complexity over that scheme requiring a single per-server exponentiation for the client and a single exponentiation for the server. As with the schemes from [10] and Camenisch et al. [4] we do not require secure channels or PKI other than in the initialization stage. We prove the security of our PPSS scheme in the Universally Composable (UC) model. For this we present a UC definition of PPSS that relaxes the UC formalism of [4] in a way that enables more efficient PPSS schemes (by dispensing with the need to extract the user's password in the simulation) and present a UC-based definition of Oblivious PRF (OPRF) that is more general than the (Verifiable) OPRF definition from [10] and is also crucial for enabling our performance optimization.
The paper examines decentralized cryptocurrency protocols that are based on the use of internal tokens as identity tools. An analysis of security problems with popular Proof-of-stake consensus protocols is provided. A new protocol, Interactive Proof-of-stake, is proposed. The main ideas of the protocol are to reduce a number of variables a miner can iterate over to a minimum and also to bring a communication into block generation. The protocol is checked against known attacks. It is shown that Interactive Proof-of-stake is more secure than current pure Proof-of-stake protocols.
<p>The password which is a more secure and valuable data should be highly protected from eavesdropper. This paper presents how password required for authentication of members of group communication is securely delivered by the source or initiator of the group. The password delivery uses zero knowledge proof and sent to the group member in an encrypted format using cipher block mode encryption. The password delivered is a One Time Password which can be used for certain amount of time in order to ensure a highly secure communication environment among the group.</p>