408 research outputs found
Procedural volume and outcomes with radial or femoral access for coronary angiography and intervention
No full textAbstract not availableSanjit S. Jolly, John Cairns, Salim Yusuf, Kari Niemela, Philippe Gabriel Steg, Matthew Worthley, Emile Ferrari, Warren J. Cantor, Anthony Fung, Nicholas Valettas, Michael Rokoss, Goran K. Olivecrona, Petr Widimsky, Asim N. Cheema, Peggy Gao, Shamir R. Mehta for the RIVAL Investigator
Attacks on the Fiat-Shamir paradigm and program obfuscation
No full textThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 115-119).The goal of cryptography is to construct *secure* and *efficient* protocols for various tasks. Unfortunately, it is often the case that protocols that are provably secure are not efficient enough for practical use. As a result, most protocols used in practice are *heuristics* that lack proofs of security. These heuristics are typically very efficient and are believed to be secure, though no proof of security has been provided. In this thesis we study the security of some of these popular heuristics. In particular, we focus on two types of heuristics: (1) the Fiat-Shamir heuristic for constructing digital signature schemes, and (2) heuristics for obfuscation. We show that, in some sense, both of these types of heuristics are insecure. Thus, this thesis consists of two parts: (1) The insecuirty of the Fiat-Shamir paradigm: The Fiat-Shamir heuristic provides a general method for transforming secure 3-round public-coin identification schemes into digital signature schemes. The idea of the transformation is to replace the random (second-round) message of the verifier in the identification scheme, with the value of some deterministic hash function evaluated on the first-round message (sent by the prover) and on the message to be signed.(cont.) The Fiat-Shamir methodology for producing digital signature schemes quickly gained popularity both in theory and in practice, as it yields efficient and easy to implement digital signature schemes. The most important question however remained open: are the digital signature schemes produced by the Fiat-Shamir methodology secure? In this thesis, we answer this question negatively. We show that there exist secure 3-round public-coin identification schemes for which the Fiat-Shamir transformation yields *insecure* digital signature schemes for *any* hash function used by the transformation. This is in contrast to the work of Pointcheval and Stern, who proved that the Fiat-Shamir methodology always produces digital signature schemes that are secure against chosen message attacks in the ``Random Oracle Model" -- when the hash function is modeled by a random oracle. (2) The impossibility of obfuscation: The goal of code obfuscation is to make a program completely "unintelligible" while preserving its functionality. Obfuscation has been used for many years in attempts to prevent reverse engineering, e.g ., in copy protection, licensing schemes, and games.(cont.) As a result, many heuristics for obfuscation have emerged, and the important question that remained is: are these heuristics for obfuscation secure? In this thesis, we show that there are many "natural" classes of functions for which obfuscation is not at all possible. This impossibility result holds in an augmentation of the formal obfuscation model of Barak, et al. (2001) that includes auxiliary input. In both of these parts, among other tools, we make new usage of Barak's technique for taking advantage of non black-box access to a program, this time in the context of digital signature schemes and in the context of obfuscation.by Yael Tauman Kalai.Ph.D
HEALTH TECHNOLOGY ASSESSMENT FOR MITRACLIP SYSTEM IN PATIENTS WITH MITRAL REGURGITATION
No full textApproximately 2% of the population have mitral regurgitation (MR) and many may be not tolerant for mitral valve surgery. The objective of this thesis was to investigate the comparative safety, effectiveness, and cost-effectiveness of percutaneous mitral valve repair using MitraClip System for patients with severe MR. Articles in MEDLINE, Embase, CNKI, and the Cochrane Library published from 1997 to February 2017 were searched for evidence of safety and effectiveness. A systematic review was conducted to address the uncertainty in the safety and effectiveness of MitraClip system in patients with MR. A cost-effectiveness analysis and cost-utility analysis in U.S. settings was conducted to address the uncertainty in health economic evaluation for the MitraClip system. One randomized trial and seven observational studies were included in the systematic review. The pooled data show that 30-day, one-year and two-year survival are similar in MitraClip arm and surgery arm. Residual MR occurs more frequently after MitraClip therapy than surgery, especially in younger patients, functional MR patients, and patients whose LVEF<50%. The risk of 30-day major adverse event from lower odds ratio appeared to be lower in older patients and patients whose LVEF≥50%.For economic evaluation, the base case incremental costs per LY and per QALY were 27,344.38 US dollars, respectively. Results were most sensitive to alternative assumptions regarding time horizon and long-term survival. Therefore, low quality of evidence due to lack of conclusive RCT data suggested that MitraClip system may provide improvements in MR, patients’ quality of life and survival advantage. It is cost-effective as threshold of $50,000 U.S. dollars per QALY gained for high surgical risk patients. Future RCT designed to reduce confounding and lessen participant attrition, which have adequate sample size, consistent reporting of outcomes, and adequate length of follow-up period will better evaluate the clinical benefits of the MitraClip System.ThesisMaster of Health Sciences (MSc)Mitral regurgitation is an abnormal leakage of blood back into the left heart chambers. About 2% of the population who have chronic mitral regurgitation are elderly and are at high risk for surgery. For such patients, a treatment has been proposed that involves a catheter puncturing the skin of the groin and travelling all the way to the affected valve to deploy a device that clips and repairs the valve leaflets (a mitral valve clip). This thesis sought to compare the safety, effectiveness and cost-effectiveness of mitral valve clips with current standards of care in patients at high risk for surgery. To address this question, we searched, critically appraised, and collated existing research evidence. We found that this new treatment was not harmful and may provide a survival advantage. In addition, the approach may be cost-effective when compared to current stand of care in patients at high risk for surgery
Android-Based Text Message Security Application With Rivest Method, Shamir, Adleman (RSA)
No full textSecurity is very important in all aspects to protect data. Text messages on mobile phones, which is sms (short messages service) is one of the
important data that needs a data security system. Data security is used to maintain the confidentiality of important data that we have on mobile devices.
The encryption process is used so that messages cannot be read by other unwanted parties. While the decryption process is used so that the message
can be read back by the intended party. Rivest Cryptography, Shamir, Adleman (RSA) is one of the asymmetric cryptographic algorithms that use a key
pair, that is the public key and private key. The key length can be set, where the longer the key formation bit, the harder it is to solve because it is difficult
to factor two very large numbers. This study applies the Rivest, Shamir, Adleman (RSA) algorithm for text message security applications based on
Android. Based on the research that has been done, the author can draw conclusions, namely: Rivest, Shamir, Adleman (RSA) cryptographic algorithm
can be implemented for text message security Android based. So it is safer to exchange text messages (SMS) so that user privacy is guarantee
Android-Based Text Message Security Application With Rivest Method, Shamir, Adleman (RSA)
No full textSecurity is very important in all aspects to protect data. Text messages on mobile phones, which is sms (short messages service) is one of the
important data that needs a data security system. Data security is used to maintain the confidentiality of important data that we have on mobile devices.
The encryption process is used so that messages cannot be read by other unwanted parties. While the decryption process is used so that the message
can be read back by the intended party. Rivest Cryptography, Shamir, Adleman (RSA) is one of the asymmetric cryptographic algorithms that use a key
pair, that is the public key and private key. The key length can be set, where the longer the key formation bit, the harder it is to solve because it is difficult
to factor two very large numbers. This study applies the Rivest, Shamir, Adleman (RSA) algorithm for text message security applications based on
Android. Based on the research that has been done, the author can draw conclusions, namely: Rivest, Shamir, Adleman (RSA) cryptographic algorithm
can be implemented for text message security Android based. So it is safer to exchange text messages (SMS) so that user privacy is guarantee
Android-Based Text Message Security Application With Rivest Method, Shamir, Adleman (RSA)
No full textSecurity is very important in all aspects to protect data. Text messages on mobile phones, which is sms (short messages service) is one of the
important data that needs a data security system. Data security is used to maintain the confidentiality of important data that we have on mobile devices.
The encryption process is used so that messages cannot be read by other unwanted parties. While the decryption process is used so that the message
can be read back by the intended party. Rivest Cryptography, Shamir, Adleman (RSA) is one of the asymmetric cryptographic algorithms that use a key
pair, that is the public key and private key. The key length can be set, where the longer the key formation bit, the harder it is to solve because it is difficult
to factor two very large numbers. This study applies the Rivest, Shamir, Adleman (RSA) algorithm for text message security applications based on
Android. Based on the research that has been done, the author can draw conclusions, namely: Rivest, Shamir, Adleman (RSA) cryptographic algorithm
can be implemented for text message security Android based. So it is safer to exchange text messages (SMS) so that user privacy is guarantee
Prediction of radial crossover in acute coronary syndromes: derivation and validation of the MATRIX score.
No full textBACKGROUND
The radial artery is recommended by international guidelines as the default vascular access in patients with acute coronary syndromes (ACS) managed invasively. However, crossover from radial to femoral access is required in 4-10% of cases and has been associated with worse outcomes. No standardised algorithm exists to predict the risk of radial crossover.
AIMS
We sought to derive and externally validate a risk score to predict radial crossover in patients with ACS managed invasively.
METHODS
The derivation cohort consisted of 4,197 patients with ACS undergoing invasive management via the randomly allocated radial access from the MATRIX trial. Using logistic regression, we selected predictors of radial crossover and developed a numerical risk score. External validation was accomplished among 3,451 and 491 ACS patients managed invasively and randomised to radial access from the RIVAL and RIFLE-STEACS trials, respectively.
RESULTS
The MATRIX score (age, height, smoking, renal failure, prior coronary artery bypass grafting, ST-segment elevation myocardial infarction, Killip class, radial expertise) showed a c-index for radial crossover of 0.71 (95% CI: 0.67-0.75) in the derivation cohort. Discrimination ability was modest in the RIVAL (c-index: 0.64; 95% CI: 0.59-0.67) and RIFLE-STEACS (c-index: 0.66; 95% CI: 0.57-0.75) cohorts. A cut-off of ≥41 points was selected to identify patients at high risk of radial crossover.
CONCLUSIONS
The MATRIX score is a simple eight-item risk score which provides a standardised tool for the prediction of radial crossover among patients with ACS managed invasively. This tool can assist operators in anticipating and better addressing difficulties related to transradial procedures, potentially improving outcomes
THE USE OF DIETARY SUPPLEMENTATION AND SUPERVISED EXERCISE PROGRAM IN CARDIAC DEVICE PATIENTS WITH ATRIAL FIBRILLATION AND FRAILTY
No full textBackground
Frailty is an aging-associated vulnerability to poor health comes when challenged by physiologic stressors. Frailty is a common problem amongst the elderly and is associated with increased mortality and health care resource utilization. Frailty is common in recipients of cardiac devices. What is not known is whether interventions will improve frailty and if this changes patient outcomes.
Methods
There are four chapters in this thesis. In chapter 1, a review of the current state of frailty research, methods of measurement, biomarkers, imaging modalities and interventions are presented. In chapter 2, a pilot randomized controlled trial is proposed to determine if a supervised exercise program and nutritional supplement improves physical frailty in cardiac device patients. Chapter 3 presents the results of the pilot study to date. In chapter 4, we discuss the challenges faced during the COVID-19 pandemic with respect to recruitment and conducting the trial and changes to the protocol that could have improved the study and adapted to the current state of research.
Results
There are two conceptual models of frailty which include the frailty phenotype and frailty index. Frailty instruments are abundant and there is no gold standard measurement. Frailty biomarkers, imaging techniques in their current state are complementary measures and are not yet ready for clinical practice. The DEFINIT P trial is single centre RCT involving 24 cardiac device patients randomized to 12 month supervised exercise program and nutritional supplement. Recruitment was halted due to COVID-19 pandemic.
Conclusions
Frailty is common in cardiac device recipients. A gold standard frailty instrument is not yet established though efforts are currently underway. The DEFINIT P study is feasible with respect to recruitment and consent targets but whether the adherence target to the exercise intervention and nutritional supplement is achieved remains unknown due to stopping the pilot trial as a result of the COVID 19 pandemic.ThesisMaster of Science (MSc)Frailty is a state of vulnerability in elderly that makes them susceptible to large declines in health from minor illnesses. Frail elderly are more likely to be admitted to the hospital, nursing homes and have higher chance of dying. Old age and frailty are not the same. Frailty is common in patients with a pacemakers and defibrillators. The purpose of this study is to test whether a supervised exercise program and a nutritional supplement will help improve frailty. We planned to recruit 24 patients into the randomized control trial and 100 patients in the registry and follow them for a period of one year. We aimed to understand how common is frailty in elderly with pacemakers and defibrillators and what factors contribute to developing frailty
Analisis Pola Identifikasi Zero Knowledge Proof dengan Algoritma Feige Fiat Shamir, Guillou Quisquater dan Schnorr pada Sistem Keamanan Informasi
No full textProtokol Zero Knowledge Proof merupakan salah satu protokol dalam Kriptografi yang memiliki tingkat keamanan yang cukup baik, karena menerapkan konsep “Truly Zero Knowledge Proof” yaitu tidak membocorkan informasi apapun. Protokol ini digunakan pada Algoritma Feige Fiat Shamir, Guillou Quisquater dan Schnorr, ketiganya merupakan Algoritma Kriptografi dengan menggunakan kunci privat dan kunci publik. Pada kunci Publik, ketiga Algoritma ini menggunakan pembangkit bilangan prima acak pada nilai p dan q untuk mendapatkan kunci publik. Untuk memastikan bilangan yang dipilih merupakan bilang prima, maka digunakan metode Rabin Miller untuk melakukan pengetesan. Pada penelitian ini, penulis akan melakukan pengujian pembangkitan kunci publik dengan menggunakan CPRNG (Cryptographically-secure Pseudo-Random Number Generator) dengan algoritma Blum Blum Shub. Pengujian akan dilakukan pada Algoritma Feige Fiat, pembentukan kunci akan menggunakan Algoritma Blum Blum Shub, namun Protokol Identifikasi tetap menggunakan Algoritma Feige Fiat Shamir. Sebelum dilakukan pengujian ini, penulis telah terlebih dahulu membandingkan dan melakukan analisa pada Algoritma Feige Fiat Shamir, Guillou Quisquater dan Schnorr. Hasil penelitian ini akan menunjukkan keberhasilan pengujian ini.Protocol Zero Knowledge Proof is one of the protocols in Cryptography that has a fairly good level of security, because it applies the concept of "Truly Zero Knowledge Proof" which is not leaking any information. This protocol is used in the Fiat Shamir, Guillou Quisquater and Schnorr Feige Algorithms, all of which are Cryptographic Algorithms using private keys and public keys. In the Public key, all three of these Algorithms use a random number generator at the values p and q to get the public key.
In this study, the author will generate a public key generation test using CPRNG (Cryptographically-secure Pseudo-Random Number Generator) with the Blum Blum Shub algorithm. The test will be conducted on the Fiat Feige Algorithm, the formation of the key will use the Blum Blum Shub Algorithm, but the Identification Protocol still uses the Fiat Shamir Feige Algorithm. Before this test is done, the authors have first compared and analyzed the Feige Shamir, Guillou Quisquater and Schnorr Algorithms. The results of this study will show the success of this test.61 HalamanTesis Magiste
Clinical update on the therapeutic use of clopidogrel: treatment of acute ST-segment elevation myocardial infarction (STEMI)
No full textHuyen Tran1, Shamir R Mehta2, John W Eikelboom21Department of Clinical Haematology, Monash Medical Centre, Victoria, Australia; 2Department of Medicine, McMaster University, Hamilton, CanadaAbstract: The pathogenesis of ST-elevation myocardial infarction (STEMI) involves plaque disruption, platelet aggregation and intracoronary artery thrombus formation. Aspirin is the cornerstone of antiplatelet therapy in patients with STEMI, reducing the risk of recurrent myocardial infarction or death during the acute phase and long term by about one-quarter. Recent large randomized trials have demonstrated that the addition of clopidogrel to aspirin reduces the risk of major ischemic events by up to a further one-third in patients with STEMI treated with fibrinolytic therapy and undergoing percutaneous coronary intervention, with no significant increase in bleeding. Thus, dual antiplatelet therapy with the combination of clopidogrel and aspirin is becoming the new standard of care for the management of patients with STEMI. Keywords: clopidogrel, antiplatelet drugs, acute coronary syndrome, myocardial infarctio
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