Developers Club geek daily blog

Reports and competitions on NeoQUEST-2015

3 years, 1 month ago
On July 2 in St. Petersburg will pass NeoQUEST-2015 which will integrate the best participants of March hackquest and guests which general hobby — information security!

We remind that anyone — free entrance can visit NeoQUEST, it is enough to guests to be registered on the action site.

Participants of hackquest are waited by 8 hours of cybersafety in the non-stop mode, and all others will be able to be educated and have a good time so at this time:
  • to listen to reports on the newest and actual in cybersafety: Android, TPM and TXT, search of password hashes of Bitcoin-purse, autofile on any net surfer, power detection of malware and many other things!
  • to see practical demonstrations: attack of team of Rutkovskaya to TXT, remote control car electronics, cracking of Bitlocker...
  • to take part in fascinating real and virtual competitions and to win various prizes: Escape-room, "Unified State Examination on IB" and a lot of things many other things!

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Task about hundred boxes and rescue of prisoners – a final accord

3 years, 1 month ago
The certain way to become history – to answer who wins chess at ideal game of both parties (white, black or friendship). Whether grand masters and supercomputers are necessary to learn truth? Or there is enough pencil, paper and beautiful idea?

The mathematics gives hope, it is possible to prove existence of object, without showing it, to find the answer, without explaining the deep reasons why it is such.

In a task about prisoners and hundred boxes a similar situation. The enormous number of possible strategy of game, one of which intuitively seemed to us the best. But whether it is possible to prove its optimality, without being submerged in medley of options?

In the post about a problem of such question it is not put. However already in the first comment to it the user of mayorovp lifts a subject, and slightly below avfonarev reports about the remarkable article revealing a secret.

It should be like especially as reasonings are simple and graceful. In general the main idea of a post not in a solution of a specific objective (that in itself is interesting too), and it is rather in once again to give a reason to be surprised to power or as Vigner was expressed, incomprehensible efficiency of mathematics.

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100 years later: the completed admissions in Ramanudzhan's records

3 years, 2 months ago

Transfer of post of Oleg Marichev and Michael Trott "After 100 Years, Ramanujan Gap Filled".
To download the file containing the text of article, interactive models and all code given in article it is possible here.
I express huge gratitude to Kirill Guzenko for the help in transfer.

Hundred years ago Srinivasa Ramanudzhan and G. H. Hardy have begun the well-known correspondence about so amazing things in mathematics that Hardy has described it as something hardly possible that to believe in it. On the first of May the 1913th year of Ramanudzhan has received constant position at University of Cambridge. In five years and one day he became the research associate of royal society, and its group became the most prestigious at that time scientific group in the world. In the 1919th year has fatally ached with Ramanudzhan during long travel by steamship Nagoya to India which took place from February 27th to March 13th. What it had everything? the notepad and the handle (yes, any Mathematica at that time), and before death it wanted to leave the equations on paper. He claimed that he has solutions for a number of functions, however time was enough for him to write some before passing to other areas of mathematics. He has written the following incomplete equation and 14 others (see. below) from which only three are at the moment solved.

One of Ramanujan&39;s unsolved equations

He died some months probably of hepatic amyobiaz. Its last notepad has been sent by University of Madras to G. H. Hardy who then has given him to the mathematician G. N. Watson. In the 1965th year when Watson has died, the principal has found notepad in its office, selecting documents for destruction. George Andrews has rediscovered this notepad in 1976 and, at last, in 1987 it has been published. Bruce Berndt and Andrews wrote about the lost Ramanudzhan's Notepad to series of books (Part 1, Part 2, and Part 3). As Berndt has told:? Opening of it? the lost notepad? has caused boom in the mathematical world same what opening of the tenth symphony of Beethoven in music world could cause?.

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The greatest small polyhedrons: new solutions in combinatory geometry

3 years, 2 months ago

Transfer of post of Ed Pegg Jr. "Biggest Little Polyhedron? New Solutions in Combinatorial Geometry".
To download the file containing the text of article, interactive models of polyhedrons and the code given in article it is possible here.
I express huge gratitude to Kirill Guzenko for the help in transfer.

In many areas of mathematics unit 1 will be the answer. Construction of non-negative number in square which is more or less unit, will give bigger or smaller number respectively. Sometimes to define, whether something is? the big?, it is necessary to find out, whether the greatest extent of this object there is more than unit. For example, huge geksagon Saturn with length of party of 13,800 km it would be possible former to carry to the big.? Small polygon?? is at what maximum distance between tops equally to unit. In 1975 Ron Graham has opened the greatest small hexagon which, as shown below, has the big area, than at the correct hexagon. Red diagonals have unit length. All other (not carried out) diagonals have smaller length.

Regular hexagon, biggest little hexagon, biggest little octagon showing lengths of 1

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Double scheduling

3 years, 2 months ago
Not so long ago has faced on service very curious task. But there is nothing new under the moon? and the task to you is familiar for a long time: double scheduling in C# in terms of static typification. I will in more detail explain below, but that who and so has understood everything, I will tell: yes, I will apply? visitor?, but it is quite unusual.

Some more reservations before formulating task more strictly: I will not stop on why I do not suit dynamic, explicit check of types through reduction and reflection. To that two reasons: 1) purpose? to get rid of runtime of exceptions 2) I want to show that language is rather expressive even if not to resort to the transferred funds and to remain within strict typification.

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Simple cryptography: frequency and differential cryptanalysis in the NeoQUEST-2015 task

3 years, 2 months ago
In anticipation of fast internal round of NeoQUEST-2015 we continue to sort online-stage tasks. The task understands article? Abracadabra?, two-piece. Both parts? on cryptoanalysis: the first? on frequency, the second? on the differential.

Participants have been given two files. The first file had the .docx format, on its first page there was that? abracadabra?? the text consisting entirely of unclear flourishes and characters, and on the second page? not quite clear list. Looking at it, one could be told precisely: here certain encryption algorithm is described.

The second file was the .txt format, it contained 2 columns entitled as plaintext and cyphertext. With all this it was necessary to do something?

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Machine gun as reactive engine: real physics of unreal flight

3 years, 2 months ago

Transfer of post of Malte Lenz "Machine Gun Jetpack: The Real Physics of Improbable Flight".
To download the file with the models considered in post it is possible here here.
I express huge gratitude to Kirill Guzenko for the help in transfer.

Whether it is possible to fly by means of the machine gun, using the reactive force arising at shots? This question has been asked in the article What if? Randall Manrou? Machine Gun Jetpack? (transfer of post into Russian). It appears that is possible because some machine guns create sufficient force to lift own weight, and can even a little more. In this post I investigate dynamics of the machine guns shooting down, and forces which are also operating thus, the generated speeds and by what height it will be possible to rise in such a way. I will also duplicate warning from article: please, do not repeat this house. For this purpose there are software environments for modeling.

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Modeling of scenarios of malfunctions of flaps of the airplane by means of Wolfram SystemModeler

3 years, 2 months ago

Transfer of post of Anneli Mossberg and Olle Isaksson "Modeling Aircraft Flap System Failure Scenarios with SystemModeler".
I express huge gratitude to Kirill Guzenko for the help in transfer.

You heard something about Boeing 747 Dreamlifter which has arrived not to that airport and has been forced to land on too short runway? Fortunately, this history had happy ending, and none of passengers have not suffered. Nevertheless, it is very dangerous situation? when actual landing distance (further? FPD) is longer than runway, and it can arise not only because of pilot error which has lost right way.

One of the possible reasons of such scenario? fault of flaps. Flaps? the hinged devices located at back edges of wings, their angular situation it is adjusted for change of lifting properties of the airplane. For example, certain position of flaps is able to allow the airplane to fly at smaller speed at ascent, or to land under more abrupt corner, thus without increasing speed. One of their main advantages consists that FPD becomes shorter. Here that puzzles me: Whether small fault of the flap can increase FPD so, what the runway band will be too short?

To answer this question, it is necessary to understand how malfunctions of separate components influence system in general. How the management system will react to it? How to find it during tests? Whether there is some safe procedure to compensate it, and what happens if the pilot or the personnel of technical maintenance for some reason do not manage to follow this procedure?


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NeoQUEST-2015: HeartBleed, Android and is a little reverse

3 years, 2 months ago
Hi, Habr! The summer, and together with it approaches?? confrontation? NeoQUEST-2015. Registration for action is already open, and input? the free. Guests are waited by reports and masterklassa on cybersafety, competitions, gifts and many other things! All this? in July, and we continue analysis of the online-stage NeoQUEST-2015 tasks. In this article:
  • ? Mystic Square??? tag? on Android and attack to RSA cryptosystem
  • ? Mason-connect?? the analysis of dump of network traffic with the subsequent implementation of vulnerability of HeartBleed
  • ? raSSLedovanie?? Man-in-the-Middle attack to Android
  • ? Friendship and brotherhood?? application reverse on C#

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Forenzika and steganography in the video file: analysis of the online-stage NeoQUEST-2015 tasks

3 years, 3 months ago
Last online-stage of annual competition in cybersafety of NeoQUEST-2015 was richest in interesting and nontrivial tasks! In this article we:
  • let's be engaged in steganography of video files and esoteric programming language of Piet, sorting task? Truth inside?
  • let's get into skin of the computer criminalist, we will work with TrueCrypt and we will answer question? And whether there was key??.

Excellent news: date is approved? confrontation? NeoQUEST-2015! Action will take place on July 2 (Thursday) in St. Petersburg, in KDTs? CLUB HOUSE?! As before, free entrance? it is only necessary to be registered on our site.

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