Theoretical Bitcoin Attacks with less than Half of the Computational Power (draft)

A widespread security claim of the Bitcoin system, presented in the original Bitcoin white-paper, states that the security of the system is guaranteed as long as there is no attacker in possession of half or more of the total computational power used to maintain the system. This claim, however, is proved based on theoretically flawed assumptions. In the paper we analyze two kinds of attacks based on two theoretical flaws: the Block Discarding Attack and the Difficulty Raising Attack. We argue that the current theoretical limit of attacker's fraction of total computational power essential for the security of the system is in a sense not $\frac{1}{2}$ but a bit less than $\frac{1}{4}$, and outline proposals for protocol change that can raise this limit to be as close to $\frac{1}{2}$ as we want. The basic idea of the Block Discarding Attack has been noted as early as 2010, and lately was independently though-of and analyzed by both author of this paper and authors of a most recently pre-print published paper. We thus focus on the major differences of our analysis, and try to explain the unfortunate surprising coincidence. To the best of our knowledge, the second attack is presented here for the first time

Pocket nickel cadmium cell and battery evaluation

The Nickel Cadmium 129-ampere hour cell was tested in order to characterize the cell under controlled conditions. Results of charge characterization and discharge characterization are reported. Ampere hour efficiency, open circuit stand, and cycle life operation results are included. The battery is briefly described

Space shuttle navigation filter development

Problems encountered in developing a high speed trajectory data processor for the shuttle ascent and entry phases are described. The development of a 19 state acceleration filter for the processor is reported

Refraction corrections for surveying

Optical measurements of range and elevation angle are distorted by the earth's atmosphere. High precision refraction correction equations are presented which are ideally suited for surveying because their inputs are optically measured range and optically measured elevation angle. The outputs are true straight line range and true geometric elevation angle. The 'short distances' used in surveying allow the calculations of true range and true elevation angle to be quickly made using a programmable pocket calculator. Topics covered include the spherical form of Snell's Law; ray path equations; and integrating the equations. Short-, medium-, and long-range refraction corrections are presented in tables

A study of accuracy in selected numerical-analysis integration techniques

Report discusses several methods of performing numerical integration with computer. When data can be expressed as state vector that is dependent variable in a differential equation, self-starting integrators can be used to predict future data

Science and ethics in the post-political era: strategies within the Camp for Climate Action

Despite a peak in activism against climate change in the UK, new environmental direct action networks have not yet received much academic attention. This article takes as a case study perhaps the most prominent of such networks – the Camp for Climate Action – which held several high-profile protest events between 2006 and 2011. Using a theoretical framework which understands society as being distinctly ‘post-political’ in character, we ask questions about the knowledge claims that form the foundations of radical environmental politics. Drawing on published statements and press releases, as well as from our insights as active participants in the Camp, we analyse the strategy of environmental protest where climate change has become its focus. The Camp for Climate Action was a contested political arena. We argue that this contestation existed over the Camp’s strategy in the context of a ‘scientised’, ‘post- political’ politics which operated within an ethical framework that prescribed individual responsibility as the primary basis for action

If you don’t let us dream, we won’t let you sleep

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