Blockchain Papers

Albert Guan, Wen-Guey Tzeng

No abstract is available for this record.

Michiel Van Beirendonck, Louis-Charles Trudeau, Pascal Giard, Alexios Balatsoukas‐Stimming

Lyra2REv2 is a hashing algorithm that consists of a chain of individual hashing algorithms and it is used as a proof-of-work function in several cryptocurrencies that aim to be ASIC-resistant. The most crucial hashing algorithm in the Lyra2REv2 chain is a specific instance of the general Lyra2 algorithm. In this work we present the first FPGA implementation of the aforementioned instance of Lyra2 and we explain how several properties of the algorithm can be exploited in order to optimize the design.

Michiel Van Beirendonck, Pascal Giard, Alexios Balatsoukas‐Stimming

No abstract is available for this record.

Ilias Giechaskiel, Cas Cremers, Kasper Rasmussen

Digital currencies such as Bitcoin rely on cryptographic primitives to operate. However, past experience shows that cryptographic primitives do not last forever: increased computational power and advanced cryptanalysis cause primitives to break and motivate the development of new ones. It is therefore crucial for maintaining trust in a cryptocurrency to anticipate such breakage. We present the first systematic analysis of the effect of broken primitives on Bitcoin. We analyze the ways in which Bitcoin’s core cryptographic building blocks can break and the subsequent effect on the main Bitcoin security guarantees. Our analysis reveals a wide range of possible effects depending on the primitive and type of breakage, ranging from minor privacy violations to a complete breakdown of the currency. Our results lead to several suggestions for the Bitcoin migration plans and insights for other cryptocurrencies in case of broken or weakened cryptographic primitives.

Phillip H. Griffin

No abstract is available for this record.

Mohammad Ahmad, Abdullah Al-Saleh, Fahad A. Al Masoud

Cryptocurrency subject attracted so many people for the last eight years around the globe. Satoshi’s Nakamoto’s, the founder of the bitcoin cryptocurrency behind this revolutionary change in digital money market. Bitcoin cryptocurrency uses “Power of Work” or simply PoW system as its mining algorithm. But in January of 2016, Ethereum cryptocurrency has launched which adopted a new system called “Power of Stake” or simply PoS that is used in Ethereum as its mining algorithm. This paper explores and compares PoW and PoS systems that is used widely today in cryptocurrencies digital money, concluding the pros and cons for each system with enabling to decide which one is more suitable and stable in digital money market.

А.А. Онацкий, Oksana Zharovа

Proposed cryptographic protocol with zero-knowledge proof on elliptic curves using one-way hash function, allowing to establish the truth of allegation and does not convey any additional information about the approval. Cryptographic protocols based on zero-knowledge proof allow identification, key exchange and other cryptographic operations to be performed without leakage of sensitive information during the information exchange. The implementation of the cryptographic protocol of the zero-knowledge proof on the basis of the mathematical apparatus of elliptic curves allows to significantly reduce the size of the protocol parameters and increase the cryptographic stability (computational complexity of the hacking problem). The security of cryptosystems on elliptic curves is based on the difficulty of solving the elliptic curve discrete logarithm problem. The completeness and correctness of the protocol is determined in the work, an example of calculation is given, the cryptographic protocol is modeled on the High-Level Protocol Specification Language, the model validation and verification of the protocol are performed. Software verification of the cryptographic protocol was performed using the software modules On the Fly Model Checker and Constraint Logic based Attack Searcher. To validation the cryptographic protocol for resistance to intruder attacks was used the Security Protocol Animator package for Automated Validation of Internet Security Protocols and Applications. The security of the proposed cryptographic protocol is based on the difficulty of solving the elliptic curve discrete logarithm problem and the cryptographic stability of the hash function. To implement the cryptographic protocol, you can use the recommended elliptical curves according to DSTU 4145-2000 and the hash function GOST 34.311-95.

Edgar González Fernández, Guillermo Morales-Luna, Feliú Sagols Troncoso

Zero-Knowledge Proofs ZKP provide a reliable option to verify that a claim is true without giving detailed information other than the answer. A classical example is provided by the ZKP based in the Graph Isomorphism problem (GI), where a prover must convince the verifier that he knows an isomorphism between two isomorphic graphs without publishing the bijection. We design a novel ZKP exploiting the NP-hard problem of finding the algebraic ideal of a multivariate polynomial set, and consequently resistant to quantum computer attacks. Since this polynomial set is obtained considering instances of GI, we guarantee that the protocol is at least as secure as the GI based protocol.

Jack Doerner, Yashvanth Kondi, Eysa Lee, Abhi Shelat

The Elliptic Curve Digital Signature Algorithm (ECDSA) is one of the most widely used schemes in deployed cryptography. Through its applications in code and binary authentication, web security, and cryptocurrency, it is likely one of the few cryptographic algorithms encountered on a daily basis by the average person. However, its design is such that executing multi-party or threshold signatures in a secure manner is challenging: unlike other, less widespread signature schemes, secure multi-party ECDSA requires custom protocols, which has heretofore implied reliance upon additional cryptographic assumptions such as the Paillier encryption scheme. We propose new protocols for multi-party ECDSA key-generation and signing with a threshold of two, which we prove secure against malicious adversaries in the random oracle model using only the Computational Diffie-Hellman Assumption and the assumptions already implied by ECDSA itself. Our scheme requires only two messages, and via implementation we find that it outperforms the best prior results in practice by a factor of 55 for key generation and 16 for signing, coming to within a factor of 12 of local signatures. Concretely, two parties can jointly sign a message in just over two milliseconds.

Amir S. Mortazavi, Mahmoud Salmasizadeh, Amir Daneshgar

No abstract is available for this record.

Norsefire, ToCsIcK

This paper introduces the underlying mechanics and interface for PhoeniχCoin (PHX), an Ethereum ERC223-compliant cryptocurrency. The supply of PHX tokens is tied directly to the Ethereum balance of the smart contract underpinning the ‘EthPhoenix’ decentralised application, and mined using a novel, generalisable technique we refer to as proof-of-volatility.

Jia Liu, Tibor Jager, Saqib A. Kakvi, Bogdan Warinschi

Time-lock encryption is a method to encrypt a message such that it can only be decrypted after a certain deadline has passed. We propose a novel time-lock encryption scheme, whose main advantage over prior constructions is that even receivers with relatively weak computational resources should immediately be able to decrypt after the deadline, without any interaction with the sender, other receivers, or a trusted third party. We build our time-lock encryption on top of the new concept of computational reference clocks and an extractable witness encryption scheme. We explain how to construct a computational reference clock based on Bitcoin. We show how to achieve constant level of multilinearity for witness encryption by using SNARKs. We propose a new construction of a witness encryption scheme which is of independent interest: our scheme, based on Subset-Sum , achieves extractable security without relying on obfuscation. The scheme employs multilinear maps of arbitrary order and is independent of the implementations of multilinear maps.

David Derler, Daniel Slamanig

No abstract is available for this record.

Fengjun Chen, Zhiqiang Liu, Long Yu, Zhen Liu · 5 authors

No abstract is available for this record.

Songjie Wei, Shuai Li, Peilong Liu, Meilin Liu

LEO constellation has received intensive research attention in the field of satellite communication. The existing centralized authentication protocols traditionally used for MEO/GEO satellite networks cannot accommodate LEO satellites with frequent user connection switching. This paper proposes a fast and efficient access verification protocol named BAVP by combining identity-based encryption and blockchain technology. Two different key management schemes with IBE and blockchain, respectively, are investigated, which further enhance the authentication reliability and efficiency in LEO constellation. Experiments on OPNET simulation platform evaluate and demonstrate the effectiveness, reliability, and fast-switching efficiency of the proposed protocol. For LEO networks, BAVP surpasses the well-known existing solutions with significant advantages in both performance and scalability which are supported by theoretical analysis and simulation results.

Maya Mohan

No abstract is available for this record.

Bram Cohen, Krzysztof Pietrzak

No abstract is available for this record.

Jie Cai, Han Jiang, Qiuliang Xu, Guangshi Lv · 6 authors

No abstract is available for this record.

Ran Canetti, Yilei Chen, Leonid Reyzin, Ron D. Rothblum

No abstract is available for this record.

Dakshita Khurana

The notion of simulation is central to cryptography: often, to demonstrate that an adversary did not recover any information about private inputs of other participants, we exhibit the existence of a simulator that generates the adversary's view without access to inputs of honest participants. The primary method used to build simulators is rewinding, where a simulator resets the adversary to a previous point in the protocol and tries to complete the protocol tree multiple times until it achieves a favorable outcome.First introduced in the context of zero-knowledge proof systems and secure computation, today the rewinding technique is synonymous with protocol security and polynomial simulation. Prior to this work, all known rewinding techniques in the plain model required multiple rounds of back-and-forth interaction between participants.In this thesis, we demonstrate the first rewinding techniques that require only a single message from each participant. Using these techniques, we overcome several barriers from literature to construct for the first time, based on standard sub-exponential cryptographic assumptions, the following core protocols, and several subsequent applications:- Two message commitments satisfying non-malleability (with respect to commitment).- Two-message delayed-input weak zero-knowledge arguments for NP. These imply arguments for NP satisfying witness hiding and strong witness indistinguishability.

Jan Hajný, Petr Dzurenda, Lukáš Malina

Card‐based physical access control systems are used by most people on a daily basis, for example, at work, in public transportation, or at hotels. Yet these systems have often very poor cryptographic protection. User identifiers and keys can be easily eavesdropped on and counterfeited. The privacy‐preserving features are almost missing in these systems. To improve this state, we propose a novel cryptographic scheme based on efficient zero‐knowledge proofs and Boneh‐Boyen signatures. The proposed scheme is provably secure and provides the full set of privacy‐enhancing features, that is, the anonymity, untraceability, and unlinkability of users. Furthermore, our scheme supports distributed multidevice authentication with multiple RFID (Radio‐Frequency IDentification) user devices. This feature is particularly important in applications for controlling access to dangerous sites where the presence of protective equipment is checked during each access control session. Besides the full cryptographic specification, we also show the results of our implementation on devices commonly used in access control applications, particularly the smart cards and embedded verification terminals. By avoiding costly operations on user devices, such as bilinear pairings, we were able to achieve times comparable to existing systems (around 500 ms), while providing significantly higher security, privacy protection, and features for RFID multidevice authentication.

Tomer Ashur, Siemen Dhooghe

The ZK-STARK technology, published by Ben-Sasson et al. in ePrint 2018/046 is hailed by many as being a viable, efficient solution to the scaling problem of cryptocurrencies. In essence, a ZK-STARK proof uses a Merkle-tree to compress the data that needs to be verified, thus greatly reduces the communication overhead between the prover and the verifier. We propose MARVELlous a family of cryptographic algorithms specifically designed for STARK efficiency. The family currently includes the block cipher Jarvis and the hash function Friday. The design of Jarvis is inspired by the design of Rijndael, better known as the AES. By doing so we create a cipher with similar properties to those of Rijndael which allows us to reuse the wide-trail strategy to argue the resistance of the design against differential and linear cryptanalysis and focus our efforts on resistance against algebraic attacks. Friday is a Merkle-Damgard based hash function instantiated with Jarvis as its compression function thus it inherits its security properties up to the birthday bound. Jarvis and Friday have been suggested to be used in the Ethereum protocol by Ben-Sasson in Ethereum's Devcon IV. In this paper, we instantiate versions of Jarvis offering 128, 160, 192 and 256-bit security (both state- and key-size) which are used to implement Friday. We warmly invite the community to study and assess the security of the designs.

Kanika Gupta, S. Sharmila Deva Selvi, C. Pandu Rangan, Shubham Sopan Dighe

No abstract is available for this record.

Fuyuki Kitagawa, Keisuke Tanaka

We propose a framework for achieving a public-key encryption (PKE) scheme that satisfies key dependent message security against chosen ciphertext attacks (KDM-CCA security) based on projective hash function. Our framework can be instantiated under the decisional diffie-hellman (DDH), quadratic residuosity (QR), and decisional composite residuosity (DCR) assumptions. The constructed schemes are KDM-CCA secure with respect to affine functions and compatible with the amplification method shown by Applebaum (EUROCRYPT 2011). Thus, they lead to PKE schemes satisfying KDM-CCA security for all functions computable by a-priori bounded size circuits. They are the first PKE schemes satisfying such a security notion in the standard model using neither non-interactive zero knowledge proof nor bilinear pairing. The above framework based on projective hash function captures only KDM-CCA security in the single user setting. However, we can prove the KDM-CCA security in the multi user setting of our concrete instantiations by using their algebraic structures explicitly. Especially, we prove that our DDH based scheme satisfies KDM-CCA security in the multi user setting with the same parameter setting as in the single user setting.