Cover photo
Malin Christersson
Works at Lund University / Campus Helsingborg
Attended Lund University
Lived in Lund
11,373 followers|2,029,672 views


Well put!
It is reported that the NSA has known about, and been actively exploiting, the 'Heartbleed' bug for at least two years, and did not at any time during those two years see fit to issue a CVE on the vulnerability.

“It flies in the face of the agency’s comments that defense comes first,” said Jason Healey, director of the cyber statecraft initiative at the Atlantic Council and a former Air Force cyber officer.  “They are going to be completely shredded by the computer security community for this.”

The article's blathering about "the weaknesses of open-source development" is sheer nonsense.  Yes, open-source code has bugs.  So does closed-source proprietary code.  ALL code has bugs, because all code is written by humans, and humans are ... well, human, and make mistakes.  The difference with open-source code is that you stand a chance of finding out about it, and once found it will be fixed, probably within days as Heartbleed was.  With closed-source, proprietary code, you may never find out about the bug, and even if the vendor finds out about the bug, they may simply decide not to fix it.  There was a known bug in Microsoft Excel that went intentionally unfixed for more than ten years, because fixing the bug would break large amounts of other Microsoft application code that was by then dependent upon the bug to work properly, and Microsoft simply couldn't be bothered.  It was easier to leave the bug unfixed.
The U.S. National Security Agency knew for at least two years about a flaw in the way that many websites send sensitive information, now dubbed the Heartbleed bug, and regularly used it to gather critical intelligence, two people familiar with the matter said.
Dick Thomas's profile photoPatrik Greco's profile photoMarc Paul Rubin's profile photoMalin Christersson's profile photo
Yes, he writes very well, and I don't think it's about "blame open source" but rather a suggestion to strengthen the open source approach, at least in this article:
Add a comment...

Malin Christersson

Shared publicly  - 
Rolling on the outside
(follow up from the posts and

If you can roll epicycloids/hypocycloids inside each other, then you can also roll them on the outside. 

I was a bit puzzled to see that the cusps of a (n+1)-hypocycloid, rolling on the outside of a n-hypocycloid,  seemed to trace out a n-epicycloid. But then I realised that it is probably obvious that they do. If you roll a n-epicycloid on the inside of a (n+1)-epicycloid, the cusps of the outer epicycloid lie on the inner epicycloid. So if you instead roll 
epicycloids on the outside, the cusps of the (n+1)-epicycloid will glide along the inner n-epicycloid. Since the cusps of 
(n+1)-epicycloids are the same points as the cusps of (n+1)-hypocycloids, it all makes sense.

The GeoGebra worksheet on GeoGebraTube:
Nisamudheen SA's profile photoMalin Christersson's profile photophilippe roux's profile photoPhil Stracchino's profile photo
Love it
Add a comment...

Malin Christersson

Shared publicly  - 
GeoGebra version of Rolling Hypocycloids

as described by John Baez, Gerard Westendorp, and commenters at:

GeoGebra Worksheet at GeoGebraTube:

Edit: Interactive version as suggested by +Boris Borcic :
 ·  Translate
Lillemor Lundin's profile photoUlrica Reimby's profile photomaie mona Messenger's profile photoMalin Christersson's profile photo
Very pretty!  It's fun to compare the version created by Greg Egan:

Here the cusps meet less often.
Add a comment...

Malin Christersson

Shared publicly  - 
Summary: It was a closely-fought contest, but Europe’s crucial telecoms package has passed through its first European Parliament vote, as have amendments that remove loopholes that would have clashed with the open internet.
Marc Paul Rubin's profile photoShaun Orwell's profile photo
Add a comment...

Malin Christersson

Shared publicly  - 
I have been to war. I have seen physical courage. But this kind of courage is not moral courage. Very few of even the bravest warriors have moral courage. For moral courage means to defy the crowd, to stand up as a solitary individual, to shun the intoxicating embrace of comradeship, to be disobedient to authority, even at the risk of your life, for a higher principle. And with moral courage comes persecution.
Shawn H Corey's profile photoSnow Andrews's profile photo
Add a comment...
Have her in circles
11,373 people

Malin Christersson

Shared publicly  - 
Sist jag postade vad Anne Ramberg skrev, tror jag att jag lovade sluta posta om henne, men det går inte att låta bli.  :-)
 ·  Translate
Det hade varit klädsamt om regeringen genast gått ut och sagt att EU-domstolens avgörande givetvis måste beaktas, skriver Anne Ramberg.
Krimean University's profile photoMartin Townsley's profile photo
Thanks Malin. GOD BLESS YOU.
Add a comment...
GeoGebra version of Rolling Epicycloids

as described by John Baez, Gerard Westendorp, and commenters at:

GeoGebra Worksheet at GeoGebraTube:

Edit: Interactive version as suggested by +Boris Borcic :
Katniss Everdeen's profile photoKadir saraç's profile photoMalin Christersson's profile photoGerard Westendorp's profile photo
Here is a new variaton. Note all cuspas, inner and outer touch:
Add a comment...

Malin Christersson

Shared publicly  - 
This should be doable using GeoGebra.
Wheels within wheels

See that small heart-shaped curve?  It's a cardioid.  You get it when you roll a circle on a circle that's the same size, and track the motion of a point on the rolling circle.

The other curves here, with more bumps, are epicycloids.  You get them when you roll a circle on a circle that's 2 times as big, or 3 times as big, etc.

It turns out there's a nice way to 'roll' each epicycloid inside the next... and that's what you see here, in this image made by Gerard Westendorp.

However, as each one rolls inside the next, it has to slip, too, for the cusps (the sharp points) to line up.

For details and more pictures like this, see:

#plane-geometry #rolling-circles
Zazuki Yamamoto's profile photoGregory Bloom's profile photoMartin Townsley's profile photo
+Zazuki Yamamoto Maybe you could design a concentric version of the Wankel engine like this?
Add a comment...
Minecraft Fractals

ScriptCraft is a Minecraft mod based on Javascript. In Scriptcraft there is a drone-object that can be used to make buildings. Using the drone-object resembles programming a turtle, the LOGO-way of doing things. Turtle programming makes some kind of recursion particularly easy, since the recursive steps are visualised - either by letting the turtle hold a pen, or by letting the drone in Scriptcraft build recursively defined buildings.

One neat thing with recursive buildings in Minecraft, is that you can choose sand as the material, and sand blocks fall down, making a different kind of recursive building.

The Young Person’s Guide to Programming in Minecraft:

Minecraft Fractals:
Daina Corey's profile photoRomain Brunias's profile photoMalin Christersson's profile photophilippe roux's profile photo
And a nice day to you +Ewa Piętka  :)
Add a comment...
Paint circle-inverted “Mondrian”!

It’s easy to draw a Mondrian-style painting and see the result after circle inversion. The real challenge is to draw a painting made of circular arcs that looks like a Mondrian-style painting after the inversion. 

Piet Mondrian on Wikipedia:
Inversive geometry on Wikipedia:
Paint Circle-Inverted Mondrian:
Leo Campos's profile photoBoris Borcic's profile photoMalin Christersson's profile photoNancy Pivarunas's profile photo
Thank you +Silvia Santos  :)
Add a comment...
Have her in circles
11,373 people
PhD student in educational research
  • Lund University / Campus Helsingborg
    PhD student, 2013 - present
Map of the places this user has livedMap of the places this user has livedMap of the places this user has lived
mathematics - computer science - digital freedom
My posts are mainly about mathematics and programming, from an educational point of view. I am currently pursuing a PhD in educational research. My research is about kids learning how to program, and the math included when doing so.
  • Lund University
    Masters degree in Computer Science/Mathematics
  • Malmö University
    Teacher Academy
Basic Information