Browsing by Author "Wagner, David"

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A Graph Approach to Quantitative Analysis of Control-Flow Obfuscating Transformations
(2009-06-01)
Tsai, Hsin-Yi
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Huang, Yu-Lun
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Wagner, David
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電控工程研究所
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Institute of Electrical and Control Engineering
Modern obfuscation techniques are intended to discourage reverse engineering and malicious tampering of software programs. We study control-flow obfuscation, which works by modifying the control flow of the program to be obfuscated, and observe that it is difficult to evaluate the robustness of these obfuscation techniques. In this paper, we present a framework for quantitative analysis of control-flow obfuscating transformations. Our framework is based upon the control-flow graph of the program, and we show that many existing control-flow obfuscation techniques can be expressed as a sequence of basic transformations on these graphs. We also propose a new measure of the difficulty of reversing these obfuscated programs, and we show that our framework can be used to easily evaluate the space penalty due to the transformations.
Estimating Sympathetic Tone by Recording Subcutaneous Nerve Activity in Ambulatory Dogs
(2015-01-01)
Robinson, Eric A.
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Rhee, Kyoung-Suk
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Doytchinova, Anisiia
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Kumar, Mohineesh
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Shelton, Richard
Subcutaneous Nerve Activity IntroductionWe tested the hypothesis that subcutaneous nerve activity (SCNA) of the thorax correlates with the stellate ganglion nerve activity (SGNA) and can be used to estimate the sympathetic tone. Methods and ResultsWe implanted radio transmitters in 11 ambulatory dogs to record left SGNA, left thoracic vagal nerve activity (VNA), and left thoracic SCNA, including 3 with simultaneous video monitoring and nerve recording. Two additional dogs were studied under general anesthesia with apamin injected into the right stellate ganglion while the right SGNA and the right SCNA were recorded. There was a significant positive correlation between integrated SGNA (iSGNA) and integrated SCNA (iSCNA) in the first 7 ambulatory dogs, with correlation coefficient of 0.70 (95% confidence interval [CI] 0.61-0.84, P < 0.05 for each dog). Tachycardia episodes (heart rate exceeding 150 bpm for 3 seconds) were invariably preceded by SGNA and SCNA. There was circadian variation of both SCNA and SGNA. Crosstalk was ruled out because SGNA, VNA, and SCNA bursts had different timing and activation patterns. In an eighth dog, closely spaced bipolar subcutaneous electrodes also recorded SCNA, but with reduced signal to noise ratio. Video monitoring in additional 3 dogs showed that movement was not a cause of high frequency SCNA. The right SGNA correlated strongly with right SCNA and heart rate in 2 anesthetized dogs after apamin injection into the right stellate ganglion. ConclusionsSCNA recorded by bipolar subcutaneous electrodes correlates with the SGNA and can be used to estimate the sympathetic tone.
Simultaneous noninvasive recording of skin sympathetic nerve activity and electrocardiogram
(2017-01)
Doytchinova, Anisiia
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Hassel, Jonathan L.
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Yuan, Yuan
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Lin, Hongbo
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Yin, Dechun
BACKGROUND Sympathetic nerve activity is important to cardiac arrhythmogenesis. OBJECTIVE The purpose of this study was to develop a method for simultaneous noninvasive recording of skin sympathetic nerve activity (SKNA) and electrocardiogram (ECG) using conventional ECG electrodes. This method (neuECG) can be used to adequately estimate sympathetic tone. METHODS We recorded neuECG signals from the skin of 56 human subjects. The signals were low-pass filtered to show the ECG and high-pass filtered to show nerve activity. Protocol 1 included 12 healthy volunteers who underwent cold water pressor test and Valsalva maneuver. Protocol 2 included 19 inpatients with epilepsy but without known heart diseases monitored for 24 hours. Protocol 3 included 22 patients admitted with electrical storm and monitored for 39.0 +/- 28.2 hours. Protocol 4 included 3 patients who underwent bilateral stellate ganglion blockade with lidocaine injection. RESULTS In patients without heart diseases, spontaneous nerve discharges were frequently observed at baseline and were associated with heart rate acceleration. SKNA recorded from chest leads (V1V6) during cold water pressor test and Valsalva maneuver (protocol 1) was invariably higher than during baseline and recovery periods (P <.001). In protocol 2, the average SKNA correlated with heart rate acceleration (r = 0.73 +/- 0.14, P <.05) and shortening of QT interval (P <.001). Among 146 spontaneous ventricular tachycardia episodes recorded in 9 patients of protocol 3, 106 episodes (73%) were preceded by SKNA within 30 seconds of onset. Protocol 4 showed that bilateral stellate ganglia blockade by lidocaine inhibited SKNA. CONCLUSION SKNA is detectable using conventional ECG electrodes in humans and may be useful in estimating sympathetic tone.
Using skin sympathetic nerve activity to estimate stellate ganglion nerve activity in dogs
(2015-06-01)
Jiang, Zhaolei
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Zhao, Ye
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Doytchinova, Anisiia
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Kamp, Nicholas J.
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Tsai, Wei-Chung
BACKGROUND Stellate ganglion nerve activity (SGNA) is important in cardiac arrhythmogenesis. However, direct recording of SGNA requires access to the thoracic cavity. Skin of upper thorax is innervated by sympathetic nerve fibers originating from the stellate ganglia and is easily accessible. OBJECTIVE The purpose of this study was to test the hypothesis that thoracic skin nerve activity (SKNA) can be used to estimate SGNA. METHODS We recorded SGNA and SKNAs using surface electrocardiogram leads in 5 anesthetized and 4 ambulatory dogs. Apamin injected into the right stellate ganglion abruptly increased both right SGNA and SKNA in 5 anesthetized dogs. We integrated nerve activities and averaged heart rate in each 1-minure window over 10 minutes, We implanted a radiotransmitter to record Left SGNA in 4 ambulatory dogs (2 normal, 1 with myocardial infarction, 1 with intermittent rapid atrial pacing). After 2 weeks of recovery, we simultaneously recorded the SKNA and Left SGNA continuously for 30 minutes when the dogs were ambulatory. RESULTS There was a positive correlation [average r = 0.877, 95% confidence interval (CI) 0.732-1.000, P<.05 for each dog] between integrated skin nerve activity (iSKNA) and SGNA (iSGNA) and between iSKNA and heart rate (average r = 0.837, 95% CI 0.752-0.923, P<.05). Similar to that found in the anesthetized dogs, there was a positive correlation (average r = 0.746, 95% CI 0.527-0.964, P<.05) between iSKNA and iSGNA and between iSKNA and heart rate (average r = 0.706, 95% CI 0.484-0.927, P<.05). CONCLUSION SKNAs can be used to estimate SGNA in dogs.