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The development of low-energy, high-performance hardware for cryptocurrency mining is gaining widespread attention. The mining process for proof-of-work (PoW) in conventional cryptocurrencies’ blockchains is increasingly being replaced by application-specific integrated circuits (ASICs). This leads to many security threats for the blockchain network because it decreases security and increases power consumption for mining. Therefore, Scrypt, the most representative ASIC-resistant algorithm, was developed to solve this problem. However, there are still some problems and challenges with the current Scrypt hardware. This article presents a new hardware architecture for the Scrypt algorithm intended for a PoW-based cryptocurrency mining system. The proposed Multi ROMix Scrypt Accelerator (MRSA) hardware architecture applies several optimization techniques: configuration, local-memory computing with high-performance pipelined Multi ROMix and rescheduling resources to significantly increase processing speed, flexibility, and energy efficiency. For evaluation, the MRSA is implemented on field-programmable gate arrays (FPGAs) to examine its actual performance, consumption, and correctness. Evaluation results on a Xilinx system-on-chip (SoC) with the ALVEO U280 Data Center Accelerator Card FPGA show that the MRSA is much more power-efficient than some of the most powerful commercial CPUs, GPUs, and other FPGA implementations. On the ALVEO U280, the MRSA achieves a maximum hash rate of 296.76 kHash/s, a throughput of 304.9 Mbps when reaching a maximum frequency of 259.94 MHz, and a power consumption of 18.12W. The energy efficiency of the MRSA on the ALVEO U280 SoC is 52.83 and 867.88 times higher than those on an RTX 3090 GPU and an i9-10940X CPU, respectively.

A password is a string of characters used to protect access to specified resources from unauthorised users. Anyone with access to the resources should be able to keep the password secret in order to prevent resources from being stolen or misused by those who do not have permission. The system that serves as a resource storage and is also in charge of granting access to those resources should be secure enough to handle access verification. The computer should have a means to validate the password in order to authenticate a person using a password. A security issue arises when a plain password is saved somewhere to be used for verification. Anyone who can identify the location where the password is kept and read it can have access to all of the system's resources. The authentication system should be able to store and validate passwords in a secure manner. With the advancement of computer hardware, the chances of cracking the security of hashing algorithms, such as Bcrypt, are increasing. Certain gear has been developed particularly to execute certain cracking algorithms at their best. To avoid the chance of cracking utilising high-end computer hardware, a more secure hashing technique is required. Argon2 is yet another hashing function that can outperform current hardware in terms of compute power. Argon2 addresses several important flaws in existing algorithms by being designed for the fastest memory filling rate and the most efficient usage of numerous processing units while still offering protection against tradeoff attacks.

Implementation of a universal and reliable cloud wallet. This document explains the design, implementation and deployment of a secure Ethereum wallet backed up by a vault of secrets on the cloud. It also introduces key concepts for this task in the field of cryptography and cybersecurity. This project is done in collaboration with the European H2020 i3-Market project. Intelligent, Interoperable, Integrative and deployable open source MARKETplace with trusted and secure software tools for incentivizing the industry data economy. Within this project, the development of a vault of secrets, such as a secure wallet on the cloud, is essential if we desire a trusted data-exchange environment backed up by the blockchain. The developed solution, named Cloud Wallet, consists of three pieces of code, each of which, serves a specific purpose within the complete project: ? Frontend Application (CloudWalletApp) ? Client Library (CloudWalletClient) ? Backend Server (CloudWalletServer) On the one hand, the frontend app allows the user to intuitively create and import Ethereum accounts in order to sign raw messages or Ethereum transactions. While the client takes care of the setup and communication with the server (among others) the app works as a UI wrapper made with the React framework for this client. To sum up, the app manages user interactions, renders the website, and uses CloudWalletClient to manage blockchain and interact with the server. On the other one, CloudWalletServer safely stores an encrypted representation of account credentials so that the client used on the application can rely on a secure credentials cloud backup to restore them back to the client in case of incidences (i.e. lost device). Additionally, it uses Key Derivation Functions to deliberately slow password-check processes and makes them expensive in terms of CPU and memory in order to discourage pre-computation attacks. This project has been developed in conjunction with Alberto Miras Gil with our university and tutor?s approval. Even though we have worked on the same project, while Alberto has focused his work on the Blockchain aspects developed exclusively at the frontend client, I have developed the security aspects of the complete solution, implemented on all frontend app, client and backend server.

We develop an economic model of an offline password cracker which allows us to make quantitative predictions about the fraction of accounts that a rational password attacker would crack in the event of an authentication server breach. We apply our economic model to analyze recent massive password breaches at Yahoo!, Dropbox, LastPass and AshleyMadison. All four organizations were using key-stretching to protect user passwords. In fact, LastPass' use of PBKDF2-SHA256 with $10^5$ hash iterations exceeds 2017 NIST minimum recommendation by an order of magnitude. Nevertheless, our analysis paints a bleak picture: the adopted key-stretching levels provide insufficient protection for user passwords. In particular, we present strong evidence that most user passwords follow a Zipf's law distribution, and characterize the behavior of a rational attacker when user passwords are selected from a Zipf's law distribution. We show that there is a finite threshold which depends on the Zipf's law parameters that characterizes the behavior of a rational attacker -- if the value of a cracked password (normalized by the cost of computing the password hash function) exceeds this threshold then the adversary's optimal strategy is always to continue attacking until each user password has been cracked. In all cases (Yahoo!, Dropbox, LastPass and AshleyMadison) we find that the value of a cracked password almost certainly exceeds this threshold meaning that a rational attacker would crack all passwords that are selected from the Zipf's law distribution (i.e., most user passwords). This prediction holds even if we incorporate an aggressive model of diminishing returns for the attacker (e.g., the total value of $500$ million cracked passwords is less than $100$ times the total value of $5$ million passwords). See paper for full abstract., Comment: IEEE Symposium on Security and Privacy (S&P) 2018

In a traditional DRAM-based main memory architecture, a memory access operation requires much more time and energy than a simple logic operation. This fact is exploited to build time-consuming and power-hungry memory-hard cryptographic functions that serve the purpose of hindering brute-force security attacks.The security of such memory-hard functions depends entirely on the non-trivial costs of memory access. However, various compute-capable memory technologies have recently emerged as promising ways to reduce the memory access bottleneck, yet no one has looked into how they may impact the security of memory-hard cryptographic functions. In this preliminary work, we investigate the impact of near-data-processing (NDP) on scrypt, a widely used memory-hard password-based key-derivation function, and discuss the opportunities to further undermine scrypt using compute-capable memory.

In cryptocurrency, a block is a record of new transactions that could mean the location of cryptocurrency, medical data, or even voting records. Once each block is completed it’s added to the chain, creating a chain of blocks: a blockchain. Because cryptocurrencies are encrypted, processing any transactions means solving complicated math problems using specified algorithm like SHA256 and Scrypt. People who solve these equations are rewarded with cryptocurrency in a process called mining. In this study the authors will find out the comparison of SHA256 and Scrypt to work on the blockchain. To find out the comparison between SHA256 and Scrypt some test will be done in this research. The test were given to both algorithm on some test System to observe which algorithm that has highest probability in finding new block. the results of the tests done in this paper show that Scrypt is much slower to hash than SHA256 but the Scrypt algorithm has greater chance to find a new block.

Osrednji predmet diplomskega dela je predstaviti zgoščevalne funkcije in algoritme, ki se uporabljajo pri doseganju porazdeljenega soglasja dokaza o delu. Opisana je tehnologija veriženja blokov ter vpliv uporabe posameznih algoritmov na učinkovitost rudarjenja kriptovalut. Predstavljena je primerjava med določenimi izbranimi algoritmi glede na procesorsko moč, ki je potrebna za njihovo izvajanje, zahtevan spominski prostor, hitrost ter druge zahtevnosti, ki so pomembne za te algoritme. Diplomsko delo je omejeno na naslednje algoritme: X11, Cryptonight, Scrypt, SHA-256 in Ethash. The main subject of diploma is to present hash functions and algorithms which are used to achieve distributed consensus based on the proof of work. In the diploma we described the blockchain technology and the influence individual algorithms have on cryptocurrency mining efficiency . A comparison is presented between certain selected algorithms based on the processing power that is required for their implementation, the required memory space, security, speed and other complexities relevant to these algortihms. The diploma is limited to the following hashing algorithms: X11, Cryptonight, Scrypt, SHA-256 and Ethash.

Lack of usability of security Application Programming In- terfaces (APIs) is one of the main reasons for mistakes that programmers make that result in security vulnerabilities in software applications they develop. Especially, APIs that pro- vide cryptographic functionalities such as password hashing are sometimes too complex for programmers to learn and use. To improve the usability of these APIs to make them easy to learn and use, it is important to identify the usability issues exist on those APIs that make those harder to learn and use. In this work, we evaluated the usability of SCrypt password hashing functionality of Bouncycastle API to identify usabil- ity issues in it that persuade programmers to make mistakes while developing applications that would result in security vulnerabilities. We conducted a study with 10 programmers where each of them spent around 2 hours for the study and attempted to develop a secure password storage solution us- ing Bouncycastle API. From data we collected, we identified 63 usability issues that exist in the SCrypt implementation of Bouncycastle API. Results of our study provided useful insights about how security/cryptographic APIs should be designed, developed and improved to provide a better experi- ence for programmers who use them. Furthermore, we expect that this work will provide a guidance on how to conduct usability evaluations for security APIs to identify usability issues exist in them., Comment: 6

Password-based key derivation functions (PBKDFs) are commonly used to transform user passwords into keys for symmetric encryption, as well as for user authentication, password hashing, and preventing attacks based on custom hardware. We propose two optimized alternatives that enhance the performance of a previously published PBKDF. This design is based on (1) employing a symmetric cipher, the Advanced Encryption Standard (AES), as a pseudo-random generator and (2) taking advantage of the support for the hardware acceleration for AES that is available on many common platforms in order to mitigate common attacks to password-based user authentication systems. We also analyze their security characteristics, establishing that they are equivalent to the security of the core primitive (AES), and we compare their performance with well-known PBKDF algorithms, such as Scrypt and Argon2, with favorable results. Research partially supported by the Spanish Government under Project Grant TEC2014-54110-R (CASUS).

Na področju sodobnih financ in bančništva se je razvila močna koncentracija kapitala v peščici finančnih središč. Kot alternativa takšni centralizaciji so se pojavile umetne deregulirane ter popolnoma distribuirane kriptografske valute. Njihova zasnova deluje na principu peer-to-peer omrežja, v katerem se s kriptografskimi funkcijami skupinsko nadzoruje transakcije in ustvarjanje same valute, kar omogoča transparentnost in hkrati anonimnost ter varnost. Za potrebe diplomskega dela smo sestavili napravo, ki z izkoriščanjem velike količine ter hitrosti pomnilnika na grafičnih karticah s posebno programsko opremo potrjuje transakcije v omrežju in nam s tem ustvarja majhen delež valute za nagrado. Opisali bomo lastnosti različnih kriptovalut, razložili metode maksimizacije dobička ter opisali uporabljeno strojno opremo. Podrobno bomo predstavili algoritem potrjevanja transakcij in prikazali vpliv konfiguracijskih parametrov na končno hitrost preračunavanja ter za konec povzeli ugotovitve. In the field of modern finance a concentration has developed in a handful of financial institutions. As an alternative to such centralization, deregulated and fully distributed synthetic currencies were introduced. They are designed as a peer-to-peer network, where through use of cryptographic functions, transactions and creation of the currency are controlled, which allows for full transparency along with anonymity and security. For purposes of this thesis we have assembled a device that uses large amounts of fast memory on video cards by running special software which confirms transactions in the network, gaining us a small proportion of the currency as a reward. We will describe characteristics of various cryptocurrencies, explain methods for maximizing profit and describe the hardware used. We will explain in detail the algorithm behind the validation of transactions, show the influence of configuration parameters on resulting hashing speed and finally draw conclusions accordingly.

Cryptocurrency, a form of digital currency that has an open and decentralized system and uses cryptography to enhance security and control the creation of new units, is touted to be the next step from conventional monetary transactions. Many cryptocurrencies exist today, with Bitcoin being the most prominent of them. Cryptocurrencies are generated by mining, as a fee for validating any transaction. The rate of generating hashes, which validate any transaction, has been increased by the use of specialized machines such as FPGAs and ASICs, running complex hashing algorithms like SHA-256 and Scrypt, thereby leading to faster generation of cryptocurrencies. This arms race for cheaper-yet-efficient machines has been on since the day the first cryptocurrency, Bitcoin, was introduced in 2009. However, with more people venturing into the world of virtual currency, generating hashes for this validation has become far more complex over the years, with miners having to invest huge sums of money on employing multiple high performance ASICs. Thus the value of the currency obtained for finding a hash did not justify the amount of money spent on setting up the machines, the cooling facilities to overcome the enormous amount of heat they produce and electricity required to run them. The next logical step in this is to utilize the power of cloud computing. Miners leasing super computers that generate hashes at astonishing rates that have a high probability of profits, with the same machine being leased to more than one person on a time bound basis is a win-win situation to both the miners, as well as the cloud service providers. This paper throws light on the nuances of cryptocurrency mining process, the traditional machines used for mining, their limitations, about how cloud based mining is the logical next step and the advantage that cloud platform offers over the traditional machines.

Most of the common password scramblers hinder password-guessing attacks by “key stretching”, e.g., by iterating a cryptographic hash function many times. With the increasing availability of cheap and massively parallel off-the-shelf hardware, iterating a hash function becomes less and less useful. To defend against attacks based on such hardware, one can exploit their limitations regarding to the amount of fast memory for each single core. The first password scrambler taking this into account was scrypt. In this paper we mount a cache-timing attack on scrypt by exploiting its password-dependent memory-access pattern. Furthermore, we show that it is possible to apply an efficient password filter for scrypt based on a malicious garbage collector. As a remedy, we present a novel password scrambler called Catena which provides both a password-independent memory-access pattern and resistance against garbage-collector attacks. Furthermore, Catena instantiated with the here introduced (G,λ)-DBH operation satisfies a certain time-memory tradeoff called λ-memory-hardness, i.e., using only 1/b the amount of memory, the time necessary to compute the password hash is increased by a factor of b λ . Finally, we introduce a more efficient instantiation of Catena based on a bit-reversal graph.

As more services move on to the web and more people use the cloud for storage of important information, it is important that providers of such services can guarantee that information is kept safe. The most common way of protecting that data is to make it impossible to access without being authenticated as the user owning the data. The most common way for a user to authenticate and thereby becoming authorized to access the data, or service, is by making use of a password. The one trying to safeguard that password must make sure that it is not easy to come by for someone trying to attack the system. The most common way to store a password is by first running that password through a one way function, known as a hash function, that obfuscates it into something that does not at all look related to the password itself. Whenever a user tries to authenticate, they type in their password and it goes through the same function and the results are compared. While this model makes sure that the password is not stored in plain text it contains no way of taking action in case the database of hashed passwords is leaked. Knowing that it is nearly impossible to be fully protected from malevolent users, the ones trying to safe guard information always need to try to make sure that it is difficult to extract information about users' passwords. Since the 70s the password storage has to a large extent looked the same. What is researched and implemented in this thesis is a different way of handling passwords, where the main focus is on making sure there are countermeasures in case the database leaks. The model described and implemented consist of software that make use of the current best practices, with the addition of encrypting the passwords with a symmetric cipher. This is all done in a distributed way to move towards a paradigm where a service provider does not need to rely on one point of security. The end result of this work is a working proof-of-concept software that runs in a distributed manner to derive users' passwords to an obfuscated form. The system is at least as secure as best current practice for storing users passwords but introduces the notion of countermeasures once information has found its way into an adversary's hands.