Privacy-focused crypto-currencies, such as Zcash or Monero, aim to provide strong cryptographic guarantees for transaction confidentiality and unlinkability.In this paper, we describe side-channel attacks that let remote adversaries bypass these protections.We present a general class of timing side-channel and traffic-analysis attacks on receiver privacy.These attacks enable an active remote adversary to identify the (secret) payee of any transaction in Zcash or Monero.The attacks violate the privacy goals of these crypto-currencies by exploiting side-channel information leaked by the implementation of different system components.Specifically, we show that a remote party can link all transactions that send funds to a user, by measuring the response time of that user's P2P node to certain requests.The timing differences are large enough that the attacks can be mounted remotely over a WAN.We responsibly disclosed the issues to the affected projects, and they have patched the vulnerabilities.We further study the impact of timing side-channels on the zero-knowledge proof systems used in these cryptocurrencies.We observe that in Zcash's implementation, the time to generate a zero-knowledge proof depends on secret transaction data, and in particular on the amount of transacted funds.Hence, an adversary capable of measuring proof generation time could break transaction confidentiality, despite the proof system's zero-knowledge property.Our attacks highlight the dangers of side-channel leakage in anonymous crypto-currencies, and the need to systematically protect them against such attacks.
The HighGear protocol (Eurocrypt 2018) is the fastest currently known approach to preprocessing for the SPDZ Multi-Party Computation scheme. Its backbone is formed by an Ideal Lattice-based Somewhat Homomorphic Encryption Scheme and accompanying Zero-Knowledge proofs. Unfortunately, due to certain characteristics of HighGear such current implementations limit the security parameters in a number of places. This is mainly due to memory and bandwidth consumption constraints. In this work we present a new approach to the ZKPoKs for the SPDZ Multi-Party Computation scheme. We rigorously formalize the original approach of HighGear and show how to improve upon it using a different proof strategy. This allows us to increase the security of the underlying protocols, whilst simultaneously also increasing the performance in terms of memory and bandwidth consumption as well as overall throughput of the SPDZ offline phase.
In a recent seminal work, Bitansky and Shmueli (STOC '20) gave the first construction of a constant round zero-knowledge argument for NP secure against quantum attacks. However, their construction has several drawbacks compared to the classical counterparts. Specifically, their construction only achieves computational soundness, requires strong assumptions of quantum hardness of learning with errors (QLWE assumption) and the existence of quantum fully homomorphic encryption (QFHE), and relies on non-black-box simulation. In this paper, we resolve these issues at the cost of weakening the notion of zero-knowledge to what is called $\epsilon$-zero-knowledge. Concretely, we construct the following protocols:
- We construct a constant round interactive proof for NP that satisfies statistical soundness and black-box $\epsilon$-zero-knowledge against quantum attacks assuming the existence of collapsing hash functions, which is a quantum counterpart of collision-resistant hash functions. Interestingly, this construction is just an adapted version of the classical protocol by Goldreich and Kahan (JoC '96) though the proof of $\epsilon$-zero-knowledge property against quantum adversaries requires novel ideas.
- We construct a constant round interactive argument for NP that satisfies computational soundness and black-box $\epsilon$-zero-knowledge against quantum attacks only assuming the existence of post-quantum one-way functions.
At the heart of our results is a new quantum rewinding technique that enables a simulator to extract a committed message of a malicious verifier while simulating verifier's internal state in an appropriate sense.
Muhammed F. Esgin, Ngoc Khanh Nguyen, Gregor Seiler
We propose a very fast lattice-based zero-knowledge proof system for exactly proving knowledge of a ternary solution \(\vec {s} \in \{-1,0,1\}^n\) to a linear equation \(A\vec {s}=\vec {u}\) over \(\mathbb {Z}_q\), which improves upon the protocol by Bootle, Lyubashevsky and Seiler (CRYPTO 2019) by producing proofs that are shorter by a factor of 8.
Emanuele Bellini, Philippe Gaborit, Alexandros Hasikos, VĂctor Mateu
The advent of quantum computers is a threat to most currently deployed cryptographic primitives. Among these, zero-knowledge proofs play an important role, due to their numerous applications. The primitives and protocols presented in this work base their security on the difficulty of solving the Rank Syndrome Decoding (RSD) problem. This problem is believed to be hard even in the quantum model. We first present a perfectly binding commitment scheme. Using this scheme, we are able to build an interactive zero-knowledge proof to prove: the knowledge of a valid opening of a committed value, and that the valid openings of three committed values satisfy a given linear relation, and, more generally, any bitwise relation. With the above protocols it becomes possible to prove the relation of two committed values for an arbitrary circuit, with quasi-linear communication complexity and a soundness error of 2/3. To our knowledge, this is the first quantum resistant zero-knowledge protocol for arbitrary circuits based on the RSD problem. An important contribution of this work is the selection of a set of parameters, and an a full implementation, both for our proposal in the rank metric and for the original LPN based one by Jain et al. in the Hamming metric, from which we took the inspiration. Beside demonstrating the practicality of both constructions, we provide evidence of the convenience of rank metric, by reporting performance benchmarks and a detailed comparison.
The main cryptographic primitives in blockchain networks are hashing functions that are designed to form short and unpredictable digests for the message entered. In blockchain networks, hashing is used to build linked block lists, which provide safe and secure storage of important information in a distributed repository. The peculiarity of the hash search problem in blockchain networks allows applying the maximum parallelization of calculations, what good are multithreaded graphics processors (GPUs). In this paper, we explore the performance of GOST 34.311, STRIBOG, KECCAK, SHA2, RIPEMD160, Blake2b, and Whirlpool cryptographic hashing algorithms. HashCat software and various GPUs were used for comparative analysis of efficiency. GPUs were used: Geforce 740M 2GB; Geforce GTX1050ti 4GB; Rx580 Aorus 4GB; Rx580 Sapphire Pulse 8GB; Sapphire Vega 56 8GB.
We initiate the study of non-interactive zero-knowledge (NIZK) arguments for languages in QMA. Our first main result is the following: if Learning With Errors (LWE) is hard for quantum computers, then any language in QMA has an NIZK argument with preprocessing. The preprocessing in our argument system consists of (i) the generation of a CRS and (ii) a single (instance-independent) quantum message from verifier to prover. The instance-dependent phase of our argument system involves only a single classical message from prover to verifier. Importantly, verification in our protocol is entirely classical, and the verifier needs not have quantum memory; its only quantum actions are in the preprocessing phase. Our second contribution is to extend the notion of a classical proof of knowledge to the quantum setting. We introduce the notions of arguments and proofs of quantum knowledge (AoQK/PoQK), and we show that our non-interactive argument system satisfies the definition of an AoQK. In particular, we explicitly construct an extractor which can recover a quantum witness from any prover which is successful in our protocol. Finally, we show that any language in QMA has an (interactive) proof of quantum knowledge.
This paper addresses the need to enhance the integrity and transparency of aircraft maintenance records in the aviation industry by using blockchain technologies. A physical aircraft maintenance logbook is susceptible to being lost or destroyed. A nonexistent aircraft maintenance logbook hurts the confidence in integrity and reputation of the aircraft. Furthermore, fraud can occur through forgery of Federal Aviation Administration (FAA) personnel signatures and the installation of non-official aircraft parts with implications to homeland security. The scope of this work is to develop a secure blockchain that can store aircraft service records and information in a digital distributed ledger. By keeping the maintenance logbook on a digital ledger, records can be stored indefinitely in a trusted environment with the integrity of records guaranteed. Additionally, to achieve being a distributed ledger, a consensus algorithm Proof of Elapsed Time (PoET) is used to display the global state accurately to all users. The proposed Secure Aircraft Maintenance Records (SAMR) blockchain uses the Linux Foundations open sourced software âHyperledgerâ to facilitate an environment that mimics a real-world implementation. The blockchain logic for SAMR implementation was made in Python through creation of a permission-based blockchain for holding the maintenance records.
In leakage resilient cryptography, there is a seemingly inherent restraint on the ability of the adversary that it cannot get access to the leakage oracle after the challenge. Recently, a series of works made a breakthrough to consider a postchallenge leakage. They presented achievable public key encryption (PKE) schemes which are semantically secure against after-the-fact leakage in the split-state model. This model puts a more acceptable constraint on adversaryâs ability that the adversary cannot query the leakage of secret states as a whole but the functions of several parts separately instead of prechallenge query only. To obtain security against chosen ciphertext attack (CCA) for PKE schemes against after-the-fact leakage attack (AFL), existing works followed the paradigm of âdouble encryptionâ which needs noninteractive zero knowledge (NIZK) proofs in the encryption algorithm. We present an alternative way to achieve AFL-CCA security via lossy trapdoor functions (LTFs) without NIZK proofs. First, we formalize the definition of LTFs secure against AFL (AFLR-LTFs) and all-but-one variants (ABO). Then, we show how to realize this primitive in the split-state model. This primitive can be used to construct AFLR-CCA secure PKE scheme in the same way as the method of âCCA from LTFsâ in traditional sense.
The smart meters become an important node for managing information about electric power system so, smart-meter drags cyber security attention in this regard. In this paper, the protocol for smart meters named as âprivacy preserving billingâ is used which provides authentication, non-repudiation and integrity by digital signature scheme and zero-knowledge proof. This protocol ensures secrecy and reliability of end to end communication. However, vulnerability lies in integrated circuits of smart meters that can leak sensitive information and side channel attacks (SCA), derive this information from integrated circuits(IC) while it's operating. The most well-known SCA's against smart-meters are electromagnetic radiations, timing and power analysis attacks. Due to side channel attacks integrated circuitâs physical and electrical effects broadcast information related to secret key and have emerged as a major vulnerability to security applications. SCA does not temper IC security as their non-invasiveness observes device under normal conditions. Hence, our ultimate goal is to make circuit of smart-meter immune against side channel attacks, specifically differential power analysis (DPA) attack is main focus, as it is more aggressive than other SCAâs. For this reason, we present basis for SCA resistance and concept of CMOS library. Secondly, the other concept, we introduces is CMOS-based digital isolation that provides immunity to electrical noise and external fields compared to optocouplers for smart-meters.
Physical Unclonable Functions (PUFs) and Hardware Security
In this paper we give an overview of the Blockchain. We explain quickly how it works thanks to the hash function and the distributed architecture. Then come the descriptions of the two most famous consensus algorithms: Proof of Work and Proof of Stake. We also present some security issues for each algorithm. This paper contains a little explanation of others consensus algorithms that are inspired of these two. Finally, a new consensus algorithm for private Blockchain is presented.
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. The most crucial and exotic hashing algorithm in the Lyra2REv2 chain is a specific instance of the general Lyra2 algorithm. This work presents the first hardware implementation of the specific instance of Lyra2 that is used in Lyra2REv2. Several properties of the aforementioned algorithm are exploited in order to optimize the design. In addition, an FPGA-based hardware implementation of a standalone miner for Lyra2REv2 on a Xilinx Multi-Processor System on Chip is presented. The proposed Lyra2REv2 miner is shown to be significantly more energy efficient than both a GPU and a commercially available FPGA-based miner. Finally, we also explain how the simplified Lyra2 and Lyra2REv2 architectures can be modified with minimal effort to also support the recent Lyra2REv3 chained hashing algorithm.
Omar A. Dawood, Othman I. Hammadi, Falath M. Mohammed
This paper proposes a new symmetric secret-key cipher for construction of block cipher model. This new approach is considered as a smart step that can be applied to the long process research of modern designing methods used in developing earlier symmetric algorithms. The present cipher can encrypt block lengths of 128-bit by employing Substitution-Permutation Network (SPN) structure. The present cipher uses three options of strong ciphering-key along with variable lengths of 192-bit for 12 rounds, 128-bit for 10 rounds and long ciphering key of 256-bit for 14 rounds similar to standard ciphers. The proposed algorithm has been designed to trust applications that are based on Bitcoin and crypto-currencies. The current algorithm intended to encrypt addresses of Bitcoin wallet that work quite similar to the e-mail address. The bitcoin wallet includes sensitive information like private secret keys and derived password that are highly confidential. The Advance Encryption Standard (AES) is employed to encrypt most of the bitcoin wallet database. The proposed cipher can act as a good substitute for the standard cipher that allows trusting the Bitcoin wallet database with high security and with a much more complex scheme. The key goal of the submitted algorithm is to build a new enhanced modern cipher with a secure and efficient applicable algorithm that can be used for crypto currencies applications employing a wide trail design strategy.
The Internet of Things (IoT) is very attractive because of its promises. However, it brings many challenges, mainly issues about privacy preservation and lightweight cryptography. Many schemes have been designed so far but none of them simultaneously takes into account these aspects. In this paper, we propose an efficient attribute-based credential scheme for IoT devices. We use elliptic curve cryptography without pairing, blind signing, and zero-knowledge proof. Our scheme supports block signing, selective disclosure, and randomization. It provides data minimization and transaction unlinkability. Our construction is efficient since smaller key size can be used, and computing time can be reduced. As a result, it is a suitable solution for IoT devices characterized by three major constraints, namely low-energy power, small storage capacity, and low computing power.
Lake Bu, Rashmi Agrawal, Hai Cheng, Michel A. Kinsy
The development and implementation of post-quantum cryptosystems have become a pressing issue in the design of secure computing systems, as general quantum computers have become more feasible in the last two years. In this work, we introduce a set of hardware post-quantum cryptographic primitives (PCPs) consisting of four frequently used security components, i.e., public-key cryptosystem (PKC), key exchange (KEX), oblivious transfer (OT), and zero-knowledge proof (ZKP). In addition, we design a high speed polynomial multiplier to accelerate these primitives. These primitives will aid researchers and designers in constructing quantum-proof secure computing systems in the post-quantum era.
Cryptography is the art of converting readable data into indecipherable format using keys and vice versa. Strength of the algorithm is mainly measured by the complexity and CPU cycles required for cryptanalysis in the algorithm. But in an energy constrained environment like IoT, CPU intense complex algorithms will degrade the efficiency. Light-weight or cut down versions of symmetric and asymmetric cryptographies are found best suited for constrained environments. So accordingly, we in this paper have surveyed a lot of Hardware and software based Light-weight cryptographic algorithms in a quest to find the best suited cryptographic algorithm for signing and hashing blockchain in a constrained environment.
Cryptographic Implementations and Security
Chaos-based Image/Signal Encryption
Advanced Steganography and Watermarking Techniques