๐บ๐ฆ ๐บ๐ฆ ๐บ๐ฆ elkement's Science/Art/Engineering blog. #StandWithUkraine ๐บ๐ฆ ๐บ๐ฆ ๐บ๐ฆ
I am writing about that PKI stuff again. I am running out of ideas for catchy introductions. So, here is a new post with old code! In Active Directory a UPN is mapped to a user automatically if it matches a user's LDAP attribute userPrincipalName (and a DNS SAN is mapped to dnsHostName).ย A Windows … Continue reading How to Add a Subject Alternative Name Safely
Take a figure of a historical patent, meticulously drawn before there was software. It's a Plural Grating Spectrograph. Wonder about the appeal of antique technical drawings. So modest, so sublime. Copy it, multiply it. Slowly rotate the color wheel, until the purples meet the reds again. This is an impossible spectrum. There are no purples … Continue reading Plural Form
I am back to my favorite security research: How to abuse certificates in a Windows / Active Directory environment! If an Active Directory integrated certification authority sign a certificate with a custom Subject Alternative Name of your choosing, you can impersonate any administrator in an AD forest. I've published two blog posts about how to … Continue reading Rogue Certificate Challenge: No Hardware Tokens, No Linux, Just a Web Server with Certificate Mapping.
You will not want to read this. Nobody does, me included. But creating it has been an interesting experiment. I have been scouring this blog for sentences, one from each blog post. In chronological order, starting in 2012. I had permitted myself to re-order sentences, but I have rarely used that option. The fountain pen … Continue reading Found Prose: Retrospective 2012-2022
He is called a pragmatic doer, knowing his physics and engineering, devoid of ideology. This is how Josef Jenni is introduced in the preface to his document called How can we achieve the energy transition (Wie erreichen wir die Energiewende). It's a manifesto and a technical overview - by the pioneer whose company had built … Continue reading Tribute to a Pragmatic Swiss Solar Pioneer – Who Called to Action in 1989
There was a time, when most articles here looked like lab reports or chapters of a thesis. Occasionally, there was a weird poem thrown in. Now is the time for art only, and the thesis-like postings provide for raw material. Temperature waves beneath the ground, driven by the oscillation of the temperature on the surface … Continue reading Loops Near the surface. Lumped Together in Space.
.... a lot had been done right after the 1973 oil embargo but there exist almost no documents on theses activities. The concerned pioneers were realizing all types of heat pump systems, sometimes day and night. But they did not care for publishing. ... says Professor of Engineering Martin Zogg, in his research report History … Continue reading Pioneers of the Oil Shock Era
I tried to avoid such words. They sounded like hollow buzzwords in times of abundance, used by advertizers playing on fears. But our complacent world is taught a lesson, right now, at furious speed. I am following news as everybody else, I am reading about gloomy forecasts. An Austria paper mill has announced today it … Continue reading Innovation and Scarcity (and Panic)
It's a relic of the Cold War era. It is black. Once shiny Bakelite became dull. Maybe it was the chemicals. It found shelter in a darkroom. In a research center dismantling its nuclear reactor. There was no future for nuclear science after the iron curtain had crumbled. It was voiceless, robbed of its carbon … Continue reading Lone Black Telephone
I have picked two colors. They shall shine in the dark. ~~~ Another version of my series Reality and Imagination. I used artistic license when tweaking the color values.
Diffraction patterns, again. But this time I tack them to an imaginary semi-circular screen. Screens grow bigger in radius with increasing wavelength - growing more reddish. If every wavelength would be diffracted in the same way, all peaks would lie on a radius of the circle. But as red is diffracted more, maxima move to … Continue reading Jellyfish of Diffraction
My creative process has been evolving gradually in the past year. ~ I am thinking about a little piece of physics, and how it is described with math. ~ Then I am creating a SageMath notebook (plus custom code) that outputs a set of functions as parametric curves in a three-dimensional space. Here, diffraction patterns … Continue reading Creative Process. Evolution.
I have been calculating diffraction patterns for visible light. Curves are displaced to turn the whole structure into a wavy ribbon built from colored wires or threads. I have turned these images into collages, adding Isaac Newton's drawings from Opticks (1704). The more I moved Newton's figures around, and the more I twisted the ribbons … Continue reading Newton’s Space Probes Investigate my Ribbons of Diffraction
A poem from my last physics posts! I have picked unedited snippets from one post, starting at the bottom and moving up, then switching to the other post and again sifting through it from bottom to top. Lines must not be rearranged: the order is dictated by the order in which snippets appeared in the … Continue reading Celestial Boosted Poetry
A spherical spaceship swooshes by at 99% of the speed of light. What will it look like? Squashed because of Lorentz contraction - like an ellipsoid? No. The outline of a moving sphere will remain spherical. Roger Penrose explained this first in 1958 - 50 years after Einstein's formulation of the theory of special relativity. … Continue reading Transforming the Celestial Sphere
I have been playing with the geometry of special relativity again! The light cone signifies the invariance of the speed of light. There is a notion of length in four-dimensional spacetime, defined as c2t2 - x2 - y2 - z2. Surfaces of constant length are 4-dimensional hyperboloids. Light rays are null rays, as light travels … Continue reading Boosted
My colorful complex function lived in a universe of white light. I turned off the light. Turned it into its negative. Expected it to look bleak. Like thin white bones on black canvas, cartoon skeletons of imaginary alien creatures. But it is more like the total solar eclipse I watched in 1999. There is interference, … Continue reading Complex Alien Eclipse
Trapped inside the light cone on a path of eerie fire. Causally connected to your past . . Onward. Celestial spheres embrace the future cone gather round your burning self.
A poem from text snippets of my last three posts, interlaced with a metamorphosis of my last drawing. ~ ~~ ~~~ The familiar wave is in the middle, oblique. accessible to intuitive interpretation. To tame it, sort of, come to rescue Or are they? Going from up to down you only care about directions What … Continue reading Familiar Wave. Come to Rescue.
Creating figures with math software does not feel like fabricating illustrations for science posts. It is more of a meditation on geometry. I want to literally draw every line. I am not using grid lines or rendered surfaces. I craft a parametric curve for every line. A curve is set of equations. Yet, playing with … Continue reading Joys of Geometry
This is a simple quantum state ... |โ> = ฮฑ|โ> + ฮฒ|โ> ... built from an up |โ> state and a down state |โ>. ฮฑ and ฮฒ are complex numbers. The result |โ> is in the middle, oblique. The oblique state is a superposition or the up and down base states. Making a measurement, you … Continue reading Spins, Rotations, and the Beauty of Complex Numbers
These - the arrangement of points in the image below - are covectors, sort of. I wrote about them, some time ago. They are entities dual to vectors. Eating vectors, spitting out numbers. Vectors are again 'co' to vectors; they will eat covectors. If vectors live in a space with axes all perpendicular to each … Continue reading Galaxies of Diffraction
look at these towers Using the map creating a distorted image projected up to the sphere All connecting rays follow this rule Imaginary number i makes an appearance that borders on the poetic Itโs nothing more than a whisper construct the proof for yourself something of a dying art avoid thinking about anything there has … Continue reading Elliptical Poetry
I've still been thinking about this elliptical cone! It has been the main character in my geometric proof on stereographic projection mapping circles to circles. The idea has been to reduce a three-dimensional problem to a two-dimensional one, by noting that something has to be symmetric. A circle on a sphere is mapped to some … Continue reading My Elliptical Cone
Using stereographic projection, you create a distorted image of the surface of a sphere, stretched out to cover an infinite plane. Each point on the sphere is mapped to a point in the equatorial plane by a projection ray starting at a pole of the sphere. Draw a circle on the sphere, e.g. by intersecting … Continue reading Circles to Circles
I poked at complex function 1/z, and its real and imaginary parts look like magical towers. When you look at these towers from above or below, you see sections of perfect circles. This is hinting at some underlying simplicity. Using the map 1/z, another complex number - w=1/z - is mapped to z. Four dimensions … Continue reading Lines and Circles
I live at the fringes of the cybersecurity community. I have never attended infosec conferences. There will be a talk on PKI hacking at Blackhat 2021 soon: Top AD offensive security gurus are presenting comprehensive research on abusing ADCS (Active Directory Certificate Services). I only know about that, because I noticed backlinks from their article … Continue reading Looking Back: Hacking and Defending Windows Public Key Infrastructure (ADCS)
Grey and colorful. Cutting through each other. Chasing each other. Meeting in the center, leaning on each other, forming an infinite line. ~ Reality and Imagination: Real and imaginary part of complex function 1/z: ~ The real part of 1/z is painted in shades of grey, the imaginary part in rainbow colors. Plots are created … Continue reading Reality and Imagination
Covectors in the Dual Space. This sounds like an alien tribe living in a parallel universe hitherto unknown to humans. In this lectures on General Relativity, Prof. Frederic Schuller says: Now comes a much-feared topic: Dual vector space. And it's totally unclear why this is such a feared topic! A vector feels familiar: three numbers … Continue reading Vintage Covectors
I've presented a Motivational Function, a while back. $latex f(z) = e^{\left(-\frac{1}{z^{2}}\right)}&s=3 $ It is infinitely flat at the zero point: all its derivatives are zero there. Yet, it manages to lift its head - as it is not analytic at zero! If you think of it as a function of a complex argument, its … Continue reading Super Motivational Function
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