Kleptography and steganography in blockchains

Despite its vast proliferation, the blockchain technology is still evolving, and witnesses continuous technical innovations to address its numerous unresolved issues. An example of these issues is the excessive electrical power consumed by some consensus protocols. Besides, although various media reports have highlighted the existence of objectionable content in blockchains, this topic has not received sufficient research. Hence, this work investigates the threat and deterrence of arbitrary-content insertion in public blockchains, which poses a legal, moral, and technical challenge. In particular, the overall aim of this work is to thoroughly study the risk of manipulating the implementation of randomized cryptographic primitives in public blockchains to mount kleptographic attacks, establish steganographic communication, and store arbitrary content. As part of our study, we present three new kleptographic attacks on two of the most commonly used digital signatures: ring signature and ECDSA. We also demonstrate our kleptographic attacks on two real cryptocurrencies: Bytecoin and Monero. Moreover, we illustrate the plausibility of hijacking public blockchains to establish steganographic channels. Particularly, we design, implement, and evaluate the first blockchain-based broadcast communication tool on top of a real-world cryptocurrency. Furthermore, we explain the detrimental consequences of kleptography and steganography on the users and the future of the blockchain technology. Namely, we show that kleptography can be used to surreptitiously steal the users' secret signing keys, which are the most valuable and guarded secret in public blockchains. After losing their keys, users of cryptocurrencies will inevitably lose their funds. In addition, we clarify that steganography can be used to establish subliminal communication and secretly store arbitrary content in public blockchains, which turns them into cheap cyberlockers. Consequently, the participation in such blockchains, which are known to store unethical content, can be criminalized, hindering the future adoption of blockchains. After discussing the adverse effects of kleptographic and steganographic attacks on blockchains, we survey all of the existing techniques that can defend against these attacks. Finally, due to the shortcomings of the available techniques, we propose four countermeasures that ensure kleptography and steganography-resistant public blockchains. Our countermeasures include two new cryptographic primitives and a generic steganographyresistant blockchain framework (SRBF). This framework presents a universal solution that deters steganography and practically achieves the right to be forgotten (RtbF) in blockchains, which represents a regulatory challenge for current immutable blockchains

Mothers\u27 Adaptation to Caring for a New Baby

To date, most research on parents\u27 adjustment after adding a new baby to their family unit has focused on mothers\u27 initial transition to parenthood. This past research has examined changes in mothers\u27 marital satisfaction and perceived well-being across the transition, and has compared their prenatal expectations to their postnatal experiences. This project assessed first-time and experienced mothers\u27 stress and satisfaction associated with parenting, their adjustment to competing demands, and their perceived well-being longitudinally before and after the birth of a baby. Additionally, how maternal and child-related variables influenced the trajectory of mothers\u27 postnatal adaptation was assessed. These variables included mothers\u27 age, their education level, their prenatal expectations and postnatal experiences concerning shared infant care, their satisfaction with the division of infant caregiving, and their perceptions of their infant\u27s temperament. Mothers (N = 136) completed an online survey during their third trimester and additional online surveys when their baby was approximately 2, 4, 6, and 8 weeks old.;First-time mothers prenatally expected a more equal division of infant caregiving between themselves and their partners than did experienced mothers. Both first-time and experienced mothers reported less assistance from their partners than they had prenatally expected. Additionally, they experienced almost twice as many violated expectations than met expectations. Growth curve modeling revealed that a cubic function of time best fit the trajectory of mothers\u27 postnatal parenting satisfaction. Mothers reported less parenting satisfaction at 4 weeks, compared to 2 and 6 weeks, and reported stability in their satisfaction between 6 and 8 weeks. A quadratic function of time best fit the trajectories of mothers\u27 postnatal parenting stress and adjustment to the demands of their baby. Mothers reported more stress and difficulty adjusting to their baby\u27s demands at 4 and 6 weeks, compared to 2 and 8 weeks. A linear function of time best fit the trajectories of mothers\u27 adjustment to home demands, generalized state anxiety, and depressive symptoms. Mothers reported less difficulty meeting home demands, less generalized anxiety, and fewer depressive symptoms across the postnatal period. Mothers\u27 violated expectations were associated with level differences in all aspects of mothers\u27 postnatal adaptation except their adjustment to home demands. Specifically, more violated expectations, in number or in magnitude, were associated with poorer postnatal adaptation. Mothers\u27 violated expectations were not associated with the slope of mothers\u27 postnatal adaptation trajectories. Exploratory models revealed that other maternal and child-related variables also impacted the level and slope of mothers\u27 postnatal adaptation.;Overall, first-time and experienced mothers were more similar than different in regards to their postnatal adaptation. This study suggests that prior findings concerning adults\u27 initial transition to parenthood may also apply to adults during each addition of a new baby into the family unit. Additionally, mothers who reported less of a mismatch between their expectations and experiences concerning shared infant care had fewer issues adapting the postnatal period. Thus, methods to increase the assistance mothers receive from their partner should be sought. Limitations of this study and suggestions for future research are also discussed

Enhancing Online Security with Image-based Captchas

Given the data loss, productivity, and financial risks posed by security breaches, there is a great need to protect online systems from automated attacks. Completely Automated Public Turing Tests to Tell Computers and Humans Apart, known as CAPTCHAs, are commonly used as one layer in providing online security. These tests are intended to be easily solvable by legitimate human users while being challenging for automated attackers to successfully complete. Traditionally, CAPTCHAs have asked users to perform tasks based on text recognition or categorization of discrete images to prove whether or not they are legitimate human users. Over time, the efficacy of these CAPTCHAs has been eroded by improved optical character recognition, image classification, and machine learning techniques that can accurately solve many CAPTCHAs at rates approaching those of humans. These CAPTCHAs can also be difficult to complete using the touch-based input methods found on widely used tablets and smartphones.;This research proposes the design of CAPTCHAs that address the shortcomings of existing implementations. These CAPTCHAs require users to perform different image-based tasks including face detection, face recognition, multimodal biometrics recognition, and object recognition to prove they are human. These are tasks that humans excel at but which remain difficult for computers to complete successfully. They can also be readily performed using click- or touch-based input methods, facilitating their use on both traditional computers and mobile devices.;Several strategies are utilized by the CAPTCHAs developed in this research to enable high human success rates while ensuring negligible automated attack success rates. One such technique, used by fgCAPTCHA, employs image quality metrics and face detection algorithms to calculate a fitness value representing the simulated performance of human users and automated attackers, respectively, at solving each generated CAPTCHA image. A genetic learning algorithm uses these fitness values to determine customized generation parameters for each CAPTCHA image. Other approaches, including gradient descent learning, artificial immune systems, and multi-stage performance-based filtering processes, are also proposed in this research to optimize the generated CAPTCHA images.;An extensive RESTful web service-based evaluation platform was developed to facilitate the testing and analysis of the CAPTCHAs developed in this research. Users recorded over 180,000 attempts at solving these CAPTCHAs using a variety of devices. The results show the designs created in this research offer high human success rates, up to 94.6\% in the case of aiCAPTCHA, while ensuring resilience against automated attacks

Advances in Geotechnical Earthquake Engineering

This book sheds lights on recent advances in Geotechnical Earthquake Engineering with special emphasis on soil liquefaction, soil-structure interaction, seismic safety of dams and underground monuments, mitigation strategies against landslide and fire whirlwind resulting from earthquakes and vibration of a layered rotating plant and Bryan's effect. The book contains sixteen chapters covering several interesting research topics written by researchers and experts from several countries. The research reported in this book is useful to graduate students and researchers working in the fields of structural and earthquake engineering. The book will also be of considerable help to civil engineers working on construction and repair of engineering structures, such as buildings, roads, dams and monuments

Creating a new Shanghai : the end of the British presence in China (1949-57)

This thesis provides a fundamental reassessment of the limits of the power of the Chinese Communist Party in the years following its takeover of China in 1949 through an examination of its policies towards eliminating British businesses from Shanghai. In the early years of the People's Republic of China, the Party sought to eliminate all foreign influence. It wanted to reset completely China's foreign relations following what was portrayed as a century of 'national humiliation'. It has previously been assumed that the CCP went about this task in a pre-planned and thoroughly ruthless manner, and that their policy making was primarily motivated by their anti-imperialist sentiments. This thesis argues that the CCP decided to take a long-term and pragmatic approach in order to prevent economic instability. Revolutionary transformative goals were compromised in order to preserve short-term stability. Rather than having a grand plan for the elimination of British businesses, the CCP's policy was often contingent and provisional. Policies directed at Chinese businesses were often adapted to pressure British businesses. The CCP lacked skills, knowledge, resources and manpower. This thesis contributes to a growing literature on China in the early 1950s by suggesting that the CCP was not strong, it was in fact weak, but that its great strength lay in its awareness of its own weaknesses and in its ability to work around them. 1.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

A study of the applicability of policy making theories in post-Mao China (1978-1995)

PhD ThesisTo examine the applicability of a range of policy making theories and models, which created by Western scholars, to the practice of post-Mao China is significant in view of what follows. First, to explore to what extent they are applicable to interpret China's practice is beneficial for both absorbing the useful elements from them and discovering and understanding the general features of China's policy making process. Second, particularly, in the post-Mao period, some remarkable changes in China's policy-making pattern have ended a period of stagnation which had lasted for nearly two centuries, and started a course of rejuvenation characterised by rapid economic growth and social prosperity. Thus, these changes and development are well worthy of study with the assistance of above-mentioned theories and models. Aiming at exploring the applicability of these theories and models and how and to what extent these changes occurred and influenced China's policy making processes in all major aspects including policy makers, motivation, policy-making methods, political environment and institutions, this thesis studied the development course (1978-1995) of China's Special Economic Zones (SEZ), which was an important programme of China's reform and opening-up strategy. In doing so, the thesis adopted a method that probes the major features, changes and development of the policy making process in post-Mao China, through examining the applicability of some selected policy making theories and models in China's practice. These selected theories and models consist of those concerning how policy is made, and those relating to how policy should be made. The above examination achieved two goals, which include (a) demonstrating the extent to which each of these theories and models can be used to observe and analyse Chinese policy making practice respectively and their reasons as well, and (b) obtaining the main findings of the thesis about China's policy making process in the post-Mao period as below. (1) Although Marxism was still the fundamental guiding thought of China's policy making, a great flexibility had been adopted, which enabled a series of new policies to be made in last two decades. (2) The twin approaches of incrementalism and pragmatism were the foundation of China's policy-making mechanism, which powerfully promoted its successful operation. (3) The rise of a pluralist tendency significantly influenced China's policy process, which included the increasing involvement of the non-CPC (Communist Party of China) or non-government political and social forces. (4) Political elites continued to dominate China's policy-making process, and this central role was much more prominent than it was in other modern countries. (5) Existing institutions were decisive in shaping China's policy-making mode, by determining the power structure and the power relations within which the policy-making actions taken place

The military lens : doctrinal differences, misperception, and deterrence failure in Sino-American relations

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Political Science, February 2005.Vita.Includes bibliographical references (p. [367]-405).Nations, because of their different strategic situations, histories, and military cultures can have dramatically different beliefs about the nature of effective military doctrine, strategy, and capabilities. This dissertation argues that when such doctrines-or "theories of victory"-differ across states, misperceptions and false optimism are likely to occur. In turn, these can impede international diplomacy and statecraft by making communication and common assessments of the balance of power more difficult. When states are engaged in strategic coercion--either deterrence or compellence--these problems can lead to escalation and war. To develop this unique explanation for the pernicious problem of false optimism, this dissertation draws on scholarship on the sources of doctrine, strategic culture, misperception, strategic coercion, and deterrence theory. It assesses the argument through case studies of attempts at strategic coercion in early Cold War Sino- American conflicts in Korea and the Taiwan Strait. The dissertation also tests the proposed theory against the conventional approach of deterrence theory that focuses on the "objective" quality of the signaling. The cases rely on process tracing using both primary and secondary sources from each side, and they support the dissertation's proposed theory in broad terms as well as in their details. The two attempts of deterrence surrounding the Korean War failed. There, the signaling between the two great powers depended heavily on each side's own doctrinal theory of victory.(cont.) These different doctrinal lenses further impeded the conduct of diplomacy between the two by blurring the interpretation of those signals as well as the overall assessment of the balance of power. In the third case (deterring conflict in the Taiwan Strait), the two sides had much more similar theories of victory, and misperception and conflict were avoided. By providing a unique analytic perspective on military capability, this dissertation suggests policymakers need to carefully consider the perceptual framework regarding military doctrine of those they are trying to influence.by Christopher P. Twomey.Ph.D

China's policy toward the Korean Peninsula from 1978 to 2000

The Korean peninsula is crucial to China's political, economic and security interests because of a combination of geographic, historical, and political circumstances. China’s economic reforms and the end of the Cold War both provided new challenges and opportunities for Northeast Asian politics. This thesis will trace the shift in the policy of the People's Republic of China toward the Korean peninsula, and the resulting shift of primacy from North Korea to South Korea, as well as from political-military security to economic development. Yet this shift was not complete. The thesis will show how China has successfully maintained relations with both North and South Korea in what can be called a "double strategy" of ideological relations with the North and economic relations with the South. The two hypotheses of my research are: 1) China's economic reform policy was the most decisive factor which made China change from a "One Korea" policy to a "Two Koreas" policy, and 2) to maximize its national interest China has deftly used the "double strategy" to keep its traditional geo-strategic and military ties with North Korea, even as it has vigorously furthered new geo-political and economic ties with South Korea. The diplomatic history of Sino-Korean relations from 1978 to 2000 will be explored through an analysis of the empirical data of primary and secondary sources taken from documents, newspapers and academic texts