This thesis presents new results in three fundamental areas of public-key cryptography: integrity, authentication and confidentiality. In each case we design new primitives or improve the features of existing ones. The first chapter, dealing with integrity, introduces a non-interactive proof for proper RSA public key generation and a contract co-signature protocol in which a breach in fairness provides the victim with transferable evidence against the cheater. The second chapter, focusing on authentication, shows how to use time measurements to shorten zeroknowledge commitments and how to exploit bias in zero-knowledge challenges to gain efficiency. This chapter also generalizes Fiat-Shamir into a one-to-many protocol and describes a very sophisticated smart card fraud illustrating what can happen when authentication protocols are wrongly designed. The third chapter is devoted to confidentiality. We propose public-key cryptosystems where traditional hardness assumptions are replaced by refinements of the CAPTCHA concept and explore the adaptation of honey encryption to natural language messages. Our final contributions focus on identity-based encryption (IBE) showing how to add broadcast features to hierarchical IBE and how to use IBE to reduce vulnerability exposure time of during software patch broadcast.
BACKGROUND: Proliferation and expansion of security risks necessitates new measures to ensure authenticity and validation of GMOs. Watermarking and other cryptographic methods are available which conceal and recover the original signature, but in the process reveal the authentication information. In many scenarios watermarking and standard cryptographic methods are necessary but not sufficient and new, more advanced, cryptographic protocols are necessary. RESULTS: Herein, we present a new crypto protocol, that is applicable in broader settings, and embeds the authentication string indistinguishably from a random element in the signature space and the string is verified or denied without disclosing the actual signature. Results show that in a nucleotide string of 1000, the algorithm gives a correlation of 0.98 or higher between the distribution of the codon and that of E. coli, making the signature virtually invisible. CONCLUSIONS: This algorithm may be used to securely authenticate and validate GMOs without disclosing the actual signature. While this protocol uses watermarking, its novelty is in use of more complex cryptographic techniques based on zero knowledge proofs to encode information.
Open access
Physical Unclonable Functions (PUFs) and Hardware Security
Riccardo Longo, Federico Pintore, Giancarlo Rinaldo, Massimiliano Sala
In recent years certification authorities (CAs) have been the target of multiple attacks due to their sensitive role in internet security. In fact, with access to malicious certificates it is possible to mount effective large-scale man-in-the-middle attacks that may become very vicious, especially if the incident is not properly handled. Many attacks, such as the 2011 ones against DigiNotar and Comodo, also show strong hints of state sponsorship; thus, CAs have to be considered primary targets in a scenario of (possibly state-sponsored) large-scale cyber attacks. Therefore, there is a need for a PKI protocol which is more resilient and without single points of failure, such as the CAs. The BIX protocol is a blockchain-based protocol that allows distribution of certificates linking a subject with their public key, hence providing a service similar to that of a PKI but without the need for a CA. In this paper, we analyse the security of the BIX protocol in a formal way. First, we identify formal security assumptions which are well-suited to this protocol. Second, we present some attack scenarios against the BIX protocol. Third, we provide formal security proofs that these attacks are not feasible under our previously established assumptions.
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.
Nesrine Khernane, Maria Potop-Butucaru, Claude Chaudet
Advances in wearable and implementable of wireless sensors have enable the development of tiny and intelligent sensors called body sensors. Monitoring the vital body parameters in real-time using wireless body area network (WBAN) has shown great potential in improving healthcare quality not only for patients but also for medical staff. However, security and privacy are still an important issue in WBANs especially in multi-hop architectures. Considering the constraints of the body sensors (namely energy, memory, computational power, etc.). In this paper, we propose and present the design and the evaluation of a secure lightweight and energy efficient authentication scheme BANZKP based on an efficient cryptographic protocol, Zero Knowledge Proof (ZKP) and a commitment scheme. ZKP is used to confirm the identify of the sensor nodes, with small computational requirement, which is favorable for body sensors given their limited resources, while the commitment scheme is used to deal with replay attacks and hence the injection attacks by committing a message and revealing the key later. BANZKP reduces the memory requirement by 56,13% compared to TinyZKP [10], the comparable alternative so far for Body Area Networks. Also, the simulation results demonstrate that our proposed scheme is 17 and 5 times more efficient in term of execution time, and uses 94.11% and 80% less energy compared to TinyZKP and W-ECDSA [16], respectively.
Nesrine Khernane, Maria Potop-Butucaru, Claude Chaudet
-Wireless body area network(WBAN) has shown great potential in improving\nhealthcare quality not only for patients but also for medical staff. However,\nsecurity and privacy are still an important issue in WBANs especially in\nmulti-hop architectures. In this paper, we propose and present the design and\nthe evaluation of a secure lightweight and energy efficient authentication\nscheme BANZKP based on an efficient cryptographic protocol, Zero Knowledge\nProof (ZKP) and a commitment scheme. ZKP is used to confirm the identify of the\nsensor nodes, with small computational requirement, which is favorable for body\nsensors given their limited resources, while the commitment scheme is used to\ndeal with replay attacks and hence the injection attacks by committing a\nmessage and revealing the key later. Our scheme reduces the memory requirement\nby 56.13 % compared to TinyZKP [13], the comparable alternative so far for Body\nArea Networks, and uses 10 % less energy.\n
Recently, the password-authenticated key exchange protocol J-PAKE of Hao and Ryan (Workshop on Security Protocols 2008) was formally proven secure in the algebraic adversary model by Abdalla et al. (IEEE S&P 2015). In this paper, we propose and examine 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. We show that they are provably secure following a similar strategy to that of Abdalla et al. We also study their efficiency as compared to J-PAKE’s, also taking into account how the groups are chosen. Namely, we treat the cases of subgroups of finite fields and elliptic curves. Our work reveals that, for subgroups of finite fields, CRS-J-PAKE is indeed more efficient than J-PAKE, while RO-J-PAKE is much less efficient. On the other hand, when instantiated with elliptic curves, both RO-J-PAKE and CRS-J-PAKE are more efficient than J-PAKE, with CRS-J-PAKE being the best of the three. Regardless of implementation, we note that RO-J-PAKE enjoys a looser security reduction than both J-PAKE and CRS-J-PAKE. CRS-J-PAKE has the tightest security proof, but relies on an additional trust assumption at setup time.
<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>
We introduce LOCATHE (Location-Enhanced Authenticated Key Exchange), a generic protocol that pools location, user attributes, access policy and desired services into a multi-factor authentication, allowing two peers to establish a secure, encrypted session and perform mutual authentication with pre-shared keys, passwords and other authentication factors. LOCATHE contributes to: (1) forward secrecy through ephemeral session keys; (2) security through zero-knowledge password proofs (ZKPP), such that no passwords can be learned from the exchange; (3) the ability to use not only location, but also multiple authentication factors from a user to a service; (4) providing a two-tiered privacy authentication scheme, in which a user may be authenticated either based on her attributes (hiding her unique identification), or with a full individual authentication; (5) employing the expressiveness and flexibility of Decentralized or Multi-Authority Ciphertext-Policy Attribute-Based Encryption, allowing multiple service providers to control their respective key generation and attributes.
Michel Abdalla⋆, Fabrice Benhamouda, Philip MacKenzie
J-PAKE is an efficient password-authenticated key exchange protocol that is included in the Open SSL library and is currently being used in practice. We present the first proof of security for this protocol in a well-known and accepted model for authenticated key-exchange, that incorporates online and offline password guessing, concurrent sessions, forward secrecy, server compromise, and loss of session keys. This proof relies on the Decision Square Diffie-Hellman assumption, as well as a strong security assumption for the non-interactive zero-knowledge (NIZK) proofs in the protocol (specifically, simulation-sound extractability). We show that the Schnorr proof-of-knowledge protocol, which was recommended for the J-PAKE protocol, satisfies this strong security assumption in a model with algebraic adversaries and random oracles, and extend the full J-PAKE proof of security to this model. Finally, we show that by modifying the recommended labels in the Schnorr protocol used in J-PAKE, we can achieve a security proof for J-PAKE with a tighter security reduction.
In this paper, we propose a novel zero knowledge grouping proof protocol for RFID Systems. Over the years, several protocols have been proposed in this area but they are either found to be vulnerable to certain attacks or do not comply with the EPC Class 1 Gen 2 (C1G2) standard because they use hash functions or other complex encryption schemes. Also, the unique design requirements of grouping proofs have not been fully addressed by many. Our protocol addresses these important security and design gaps in grouping proofs. We present a novel approach based on pseudo random squares and quadratic residuosity to realize a zero knowledge system. Tag operations are limited to functions such as modulo (MOD), exclusive-or (XOR) and 128 bit Pseudo Random Number Generators (PRNG). These can be easily implemented on passive tags and hence achieves compliance with the EPC Global standard while meeting the security requirements.
The role-based access control (RBAC) is a natural and versatile model of the access control principle. In the real world, it is common that an organization provides a service to a user who owns a certain role that was issued by a different organization. However, such a trans-organizational RBAC is not common in a computer network because it is difficult to establish both the security that prohibits malicious impersonation of roles and the flexibility that allows small organizations/individual users to fully control their own roles. This study proposes a system that makes use of Bitcoin technology to realize a trans-organizational RBAC mechanism. Bitcoin, the first decentralized digital currency, is a payment network that has become a platform for innovative ideas. Bitcoin’s technology, including its protocol, cryptography, and open-source nature, has built a good reputation and has been applied in other applications, such as trusted timestamping. The proposed system uses Bitcoin technology as a versatile infrastructure to represent the trust and endorsement relationship that are essential in RBAC and to realize a challenge-response authentication protocol that verifies a user's ownership of roles.
Feroz Ahmad Ahmad, Prashant Kumar, Gulshan Shrivastava, Med Salim Bouhlel
ON 12 JANUARY 2009 a pseudonymous entity signed a transaction that instructed a distributed network to transfer a small amount of digital currency to Hal Finney, one ofthe key figures of the cypherpunk movement. After a few minutes, the transaction was recorded on a distributed public ledger, permanently updating the balance ofbothparties. This transaction— the first Bitcoin transaction—marked the beginning of a new era of decentralized payment systems, ushering in a variety of financial Services that do not depend on any centralized clearinghouse or other financial middleman. Bitcoin is regarded by many as a powerful technological innovation that could disrupt many sectors, in the realm of finance and beyond. But the underlying technology on which the network operates, the Bitcoin blockchain can do much more than that. Just as the internet did in the early-1990s, blockchain technology carries with it a whole new range of promises concerning how decentralization can support and promote individual freedoms and autonomy. Blockchain proponents believe that Bitcoin and other cryptocurrency platforms will revolutionize mechanisms of value exchange in the same way that the internet transformed information sharing, by providing a platform for people to exchange digital resources, in a secure and decentralized manner without the need to rely on any intermediary or trusted authority. But this revolutionary potential also carries with it serious implications for censorship, intellectual property, and the regulated flow of information. A blockchain is a decentralized database of transactions maintained by a distributed network of computers, which all contribute to the verification and the validation of transactions. Once accepted, these transactions are recorded inside a “block” of transactions, which incorporates a reference to previous blocks. This creates a long chain of blocks—a “blockchain”—that stores the history of all transactions in a chronological order. Every block contains information about a particular set of transactions, a reference to the preceding block in the blockchain, and the answer to a complex mathematical puzzle that is used to validate the data associated with that block. A copy of the blockchain is stored on every computer in the network, making it virtually impossible for anyone unilaterally to modify the data stored on this decentralized database: if anyone tries to modify any transaction the fraud will be immediately detected by all other network participants.
Open access
43 source records
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
In this paper, we propose a secure yoking proof protocol for RFID passive tags based on Zero Knowledge. The protocols that have been proposed earlier are either found to be vulnerable to certain attacks or do not comply with EPC standard for passive tags because they use complex encryption schemes. Also, the unique design requirements of yoking/grouping proofs have not been fully addressed by many. Our protocol addresses these important security and design gaps in yoking proofs. The proposed protocol uses pseudo random squares and quadratic residuosity to realize the zero knowledge property. Tag operations are limited to functions such as modulo (MOD), exclusive-or (XOR) and 128-bit Pseudo Random Number Generators (PRNG). Passive tags are capable of these operations and hence the protocol achieves EPC compliance and also meets the necessary security requirements.
In this paper, we describe our analysis of a recently proposed electric vehicle charing protocol. The protocol builds on complicated cryptographic primitives such as commitment, zero-knowledge proofs, BBS+ signature and etc. Moreover, interesting properties such as secrecy, authentication, anonymity, and location privacy are claimed on this protocol. It thus presents a challenge for formal verification, as existing tools for security protocol analysis lack support for all the required features. In our analysis, we employ and combine the strength of two state-of-the-art symbolic verifiers, Tamarin and Prove if, to check all important properties of the protocol.
Joseph A. Akinyele, Gilles Barthe, Benjamin Grégoire, Benedikt Schmidt · 5 authors
Many algorithms admit very efficient batch versions that compute simultaneously the output of the algorithms on a set of inputs. Batch algorithms are widely used in cryptography, especially in the setting of pairing-based computations, where they deliver significant speed-ups. Auto Batch is an automated tool that computes highly optimized batch verification algorithms for pairing-based signature schemes. Thanks to finely tuned heuristics, Auto Batch is able to rediscover efficient batch verifiers for several signature schemes of interest, and in some cases to output batch verifiers that outperform the best known verifiers from the literature. However, Auto Batch only provides weak guarantees (in the form of a LaTeX proof) of the correctness of the batch algorithms it outputs. In this paper, we verify the correctness and security of these algorithms using the Easy Crypt framework. To achieve this goal, we define a domain-specific language to describe verification algorithms based on pairings and provide an efficient algorithm for checking (approximate) observational equivalence between expressions of this language. By translating the output of Auto Batch to this language and applying our verification procedure, we obtain machine-checked correctness proofs of the batch verifiers. Moreover, we formalize notions of security for batch verifiers and we provide a generic proof in Easy Crypt that batch verifiers satisfy a security property called screening, provided they are correct and the original signature is unforgeable against chosen-message attacks. We apply our techniques to several well-known pairing-based signature schemes from the literature, and to Groth-Sahai zero-knowledge proofs.
The practical deployment of vehicular networks is still a pending issue. In this paper we describe a new self-organized method of authentication for VANETs, which allows their widespread, fast and secure implementation. Our proposal does not involve any central certification authority because the nodes themselves certify the validity of public keys of the other nodes. On the one hand we propose an algorithm that each node must use to choose the public key certificates for its local store. On the other hand, we also describe a new node authentication method based on a cryptographic protocol including a zero-knowledge proof that each node must use to convince another node on the possession of certain secret without revealing anything about it, which allows non-encrypted communication during authentication. Thanks to the combination of the aforementioned tools, the cooperation among vehicles can be used for developing several practical applications of VANETs, such as detection and warning about abnormal traffic conditions. One of the most interesting aspects of our proposal is that it only requires existing devices such as smartphones, because the designed schemes are fully distributed and self-organized. In this work we include an analysis of both an NS-2 simulation and a real device implementation of the proposed algorithms, which enables us to extract promising conclusions and several possible improvements and open questions for further research.
J-PAKE is a Password-Authenticated Key Exchange protocol, proposed in 2008 and presented again in 2010 and 2011. It does not require any public key infrastructure but uses zero-knowledge proofs. J-PAKE has been submitted as a candidate for the IEEE P1363.2 standard for password-based public key cryptography, and included in OpenSSL and OpenSSH. Since December 2010, J-PAKE has been used in Mozilla Firefox web browser. In this paper, we show that J-PAKE is vulnerable to password compromise impersonation attack, replay attack, and unknown key-share attack. We also propose some improvements for thwarting replay and unknown key-share attacks.
Recently, smart devices for various services have been developed using converged telecommunications, and the markets for near field communication mobile services is expected to grow rapidly. In particular, the realization of mobile NFC payment services is expected to go commercial, and it is widely attracting attention both on a domestic and global level. However, this realization would increase privacy infringement, as personal information is extensively used in the NFC technology. One example of such privacy infringement would be the case of the Google wallet service. In this paper, we propose an zero-knowledge proof scheme and ring signature based on NTRU for protecting user information in NFC mobile payment systems without directly using private financial information of the user.
최근 스마트 기기는 결제, 할인쿠폰 등 각종 기능을 제공하는 수단으로 진화되면서 통신과 금융이 융합된 모바일 NFC 서비스의 시장이 급성장할 것으로 전망되고 있다. 특히 모바일 NFC 결제 서비스 시장의 활성화가 예상됨에 따라 모바일 NFC 결제 서비스는 국내 외적으로 널리 주목받고 있다. 하지만 이에 따른 NFC 기술 활용 증가로 개인정보 이용이 늘면서 침해요소 또한 증가하고 있다. 최근 한국인터넷진흥원에서 발표한 "NFC 개인정보보호 대책 최종보고서"에 따르면 개인정보 암호화를 부분적으로 미지원하거나 불필요한 개인정보의 과도한 수집 및 저장 등이 문제점으로 제기되었으며 Google사의 Google Wallet 서비스의 개인정보 유출 사고 또한 이러한 문제점을 뒷받침하는 근거가 되고 있다. 본 논문에서는 기존에 서비스되고 있는 NFC 모바일 결제 서비스 상에서 결제정보의 이동 경로 별 결제 기술의 위협을 분석하고 OTA(Over the Air) 상에서 안전한 정보교환을 위한 NTRU 기반 상호인증 기법과 사용자와 은행 간의 결제 단계에서 결제정보를 직접적으로 사용하지 않고 결제자를 증명할 수 있는 NTRU기반 영지식 증명 기법에 대해 제안한다. Recently, smart devices for various services have been developed using converged telecommunications, and the markets for near field communication (NFC) mobile services is expected to grow rapidly. In particular, the realization of mobile NFC payment services is expected to go commercial, and it is widely attracting attention both on a domestic and global level. However, this realization would increase privacy infringement, as personal information is extensively used in the NFC technology. One example of such privacy infringement would be the case of the Google wallet service. In this paper, we propose an mutual authentication scheme based on NTRU for secure channel in OTA and an zero-knowledge proof scheme NTRU based on for protecting user information in NFC mobile payment systems without directly using private financial information of the user.