Blockchain technology started as the backbone for cryptocurriencies and it has emerged as one of the most interesting technologies of the last decade. It is a new paradigm able to modify the way how industries transact. Today, the industries’ concern is about their ability to handle a high volume of data transactions per second while preserving both decentralization and security. Both decentralization and security are guaranteed by the mathematical strength of cryptographic primitives. There are two main approaches to achieve consensus: the Proof-of-Work based blockchains—PoW—and the Proof-of-Stake—PoS. Both of them come with some pros and drawbacks, but both rely on cryptography. In this survey, we present a review of the main consensus procedures, including the new consensus proposed by Algorand: Pure Proof-of-Stake—Pure PoS. In this article, we provide a framework to compare the performances of PoW, PoS and the Pure PoS, based on throughput and scalability.

Background: Metals are suspected of being involved in the pathogenesis of various neurologic diseases. We previously found a complex imbalance in serum chemical elements and oxidative status in patients with clinically definite multiple sclerosis (CDMS). Objective: To understand whether this imbalance affects people with clinically isolated syndrome (CIS) and, if so, whether it predicts conversion to CDMS. Methods: We studied 22 chemical elements and the oxidative status in 49 patients with CIS, 49 patients with CDMS, and 49 healthy donors (HD). Univariate and multivariate approaches were used to identify profiles for each group. A logistic regression analysis was used to identify the predictive potential of baseline data (elements, oxidative status, and MRI findings) for conversion to CDMS over 36 months. Results: Several elements and oxidative status values differed significantly among the 3 groups. Discriminant analysis revealed a major contribution of Ca, Fe, Sn, Zn, serum antioxidant capacity, and serum oxidative status, which resulted in distinct profiles (the prediction of group membership was 96% [cross-validated 92%] for HD, 92% [cross-validated 92%] for CDMS, and 90% [cross-validated 86%] for CIS). A weighted combination of element concentrations and oxidative status values, adjusting for all other predictors, would predict a reduction in the risk of conversion to CDMS within 3 years (odds ratio 0.37; 95% confidence interval 0.18–0.76; p = 0.007), thereby proving more effective than MRI at baseline. Conclusions: The peculiar imbalance in serum elements and oxidative status that characterizes patients with CIS and may predict conversion to CDMS warrants studies on larger sample sizes.

PBKDF2 is a well-known password-based key derivation function. In order to slow attackers down, PBKDF2 introduces CPU-intensive operations based on an iterated pseudorandom function (in our case HMAC-SHA-1). If we are able to speed up a SHA-1 or an HMAC implementation, we are able to speed up PBKDF2-HMAC-SHA-1. This means that a performance improvement might be exploited by regular users and attackers. Interestingly, FIPS 198-1 suggests that it is possible to precompute first message block of a keyed hash function only once, store such a value and use it each time is needed. Therefore the computation of first message block does not contribute to slowing attackers down, thus making the computation of second message block crucial. In this paper we focus on the latter, investigating the possibility to avoid part of the HMAC-SHA-1 operations. We show that some CPU-intensive operations may be replaced with a set of equivalent, but less onerous, instructions. We identify useless XOR operations exploiting and extending Intel optimizations, and applying the Boyar-Peralta heuristic. In addition, we provide an alternative method to compute the SHA-1 message scheduling function and explain why attackers might exploit these findings to speed up a brute force attack against PBKDF2.