Question about DES S-boxes from Encryption to Decryption While working on a homework assignment, I came across an interesting dilemma that I want to delve more into. The question essentially said to flip the first bit in the key string and then see what S boxes it will effect. Then it says to do the same for decryption.   I went through the process of doing this encryption and then decryption and found that each process is the exact opposite. This makes sense logically but I feel like that is not as... secure? Would the S boxes be the exact same in the decryption phase as in the encryption phase just in reverse? Wouldn't there be a way to sense the pattern here? I know DES is not the most secure system anyway but this seems even more unsecured? I'm just a bit confused on how the math from encryption to decryption works. Clearly it isn't linear but it seems like it?
How does DES decryption work? Is it the same as encryption or the reverse? If DES decryption is the same as encryption done in reverse order, then how can the reversed S-Box convert 4 bits into 6 bits?
Currently selected indicator's colour in flag summary and help pages, can be the same as the site's colour code Some of the Stack Exchange sites has it's own colour code. Like Meta Stack Exchange has #17a7db, ELU has #AE3737, Travel has #277789 for the currently selected item's indicators in main page and the user activity page. But in the flag summary section and help pages of those sites, the indicator has the colour of #F48024 which is same as the Stack Overflow site's colour code. So instead of applying the Stack Overflow's colour code to all the sites, shall we apply the site's specific colour code in flag summary and help pages too. Selected indicator in flag summary section of MSE, ELU and Travel:      Selected indicator in help page: Book recommendation on plane Euclidean geometry I consider myself relatively good at math, though I don't know it at a high level (yet). One of my problems is that I'm not very comfortable with geometry, unlike algebra, or to restate, I'm much more comfortable with algebra than geometry. I think that's mainly because my geometry education was sparse through the years, lacking in consistency etc. So I'd like to revise (and learn more) all at once, catching the basic axioms, understanding why such is such, etc. Essentially, a moderately rigorous textbook in plain Euclidean geometry (nothing fancy). Please don't say "The Elements" - I have browsed it at the bookstore, it is quite good, but not really what I'm looking for right now. I'm currently studying  and Python programming. I just want to know how I would go about executing a Linux command in Python. The commands I want to execute are:  echo 1 &gt; /proc/sys/net/ipv4/ip_forward iptables -t nat -A PREROUTING -p tcp --destination-port 80 -j REDIRECT --to-port 8080   If I just use print in Python and run it in the terminal will it do the same as executing it as if you was typing it yourself and pressing Enter? I have some Java executable (jar) that is run my some shell script from a cron job once every night. That executable does not print log statements &quot;as usual&quot; just by printing them out in a sequential manner like line after line (print after print), but while it processes its data its printing a single line with status data and then &quot;overwrite&quot; or &quot;update&quot; just that single line over and over again, until its done with this part of processing. Examples: A common program would output something line this: Program XYZ started..&lt;cr+lf&gt; processing 1&lt;cr+lf&gt; processing 2&lt;cr+lf&gt; processing 3&lt;cr+lf&gt; im done&lt;cr+lf&gt;  Simple! I can easily redirect its output to a file and I'm done. But the program I will have to deal with does it more like this: Program XYZ started..&lt;cr+lf&gt; processing 1&lt;cr&gt; processing 1 - part a&lt;cr&gt; processing 1 - part b&lt;cr&gt; processing 1 - part c&lt;cr&gt; processing 1 - part d&lt;cr&gt; &lt;cr+lf&gt; processing 2&lt;cr&gt; processing 2 - part a&lt;cr&gt; processing 2 - part b&lt;cr&gt; processing 2 - part c&lt;cr&gt; processing 2 - part d&lt;cr&gt; &lt;cr+lf&gt; processing 3&lt;cr+lf&gt; im done&lt;cr+lf&gt;  but much more intensive than I showed here. So it just not always overwrite status lines, but does it a lot while processing. So just redirecting or appending its output to a log file does not seem to make a lot of sense here, since it will just clutter the log file with millions of screen-updates that can not be viewed and understood that easily by humans. So my question is: is there a way or tool for programs that may behave like that to &quot;log&quot; or maybe &quot;screenshot every 30 seconds&quot; their output to a log file? I have noticed for a few months that my mouse will randomly jerk across the screen. I'm super paranoid about security. But this is just silly!  Has anyone else experienced this, and found out what causes it? It happens to me every couple of days. The cursor will jump across the screen about 1000+ pixels. I thought it was my mousepad - changed it, and that's not it.  I imagine it's just a hardware issue.  This is on a PC with a Razer Naga, wired mouse. The mouse worked for about a year before I started noticing these issues. They have persisted even after a reformat / reinstall. Why is the speed of light defined as 299792458 m/s? Why is the speed of light defined as $299792458$ $m/s$? Why did they choose that number and no other number?  Or phrased differently:  Why is a metre $1/299792458$ of the distance light travels in a sec in a vacuum? Why doesn't "cd" work in a shell script? I just want to write a script which changes my directory.  I put the below commands in the file /home/alex/pathABC  #!/bin/sh cd /home/alex/Documents/A/B/C echo HelloWorld   I did   chmod +x pathABC   In the Terminal, while in /home/alex, I ran ./pathABC, but the output is just HelloWorld and the current directory is not changed.  So what is wrong? Why constructors will always have same name as of class and how they are invoked implicitly? $$(1+2+\cdots+n)^2=1^3+2^3+\cdots+n^3$$  I noticed this only because $\displaystyle \sum_{i=1}^n i = \frac{n(n+1)}{2}$ and $\displaystyle \sum_{i=1}^n i^3 = \frac{n^2(n+1)^2}{4}$.  But the two things look completely different and I can't think of an intuitive reason I would have seen this connection. Something like the 'Proof Without Words' images. Or a trick I could use while expanding the right hand side to transform it to the sum of cubes. Why does bash say No such file or directory when the file is on the path Sorry for asking such a basic question - but is there an actual term for the numbers that appear before and after the decimal point?  Example:  25.18  I know the 1 is in the tenths position, the 8 is in the hundredths position. are there singular terms which apply to all of the numbers that appear both before and after the decimal point?  I'm building a billing system, storing dollars and cents as integers (in separate columns), but for other currencies "dollars" and "cents" are not the correct terms = ).  Thanks! No feedback when comment fails to post on Android 2.3.5 In the mobile theme on Android 2.3.5, comments that do not meet the minimum length will fail to post but no feedback message is displayed to the user.  The submit button changes to its active state, but nothing else happens. How do I get from Terminal 1 to Terminal 5 in Fiumicino Airport? The official site mentions a shuttle bus service, I also googled but the infos are not clear, so I hope to find some firsthand experience.  I have a flight with a stop in Fiumicino, I will arrive in Terminal 1 and the next departure is from Terminal 5, the transfer time is around 5 hours.  Is it correct that I should go to Terminal 3 first (using the internal transfer area) and after exit from Terminal 3 and take the shuttle to Terminal 5?  The terminal 5 has a waiting area with some shops or is just a terminal for departure? In your opinion is better to wait some hours inside Terminal 3 before going out to take the shuttle bus? What is the logic behind the timer of the Sojourner Badge? "No root filesystem is defined" while installing Ubuntu I have just got a new laptop, It is running Windows 7 Home Premium.  I have shrunk the windows partition to give me some empty space and now I want to install ubuntu.  From Windows my partitions look like:   So now in the ubuntu live cd If I hit install and go manual the partitioner looks like   So I thought I could just select the empty space and be away laughing, but when I hit it I get get the Eyes of the Dark feature (XGtE, p. 51):     When you reach 3rd level in this class you learn the darkness spell [...] If you cast it with sorcery points, you can see through the darkness created by the spell.   Does this mean that if a Shadow Sorcerer casts darkness using sorcery points and then moves into a different area of magical darkness (not the one s/he created), the Sorcerer would not be able to see?  Or does the ability mean that the Sorcerer would possess the ability to see through the magical darkness created by the darkness spell in general (provided they were maintaining their own casting of the spell)? Can I store my pixels somewhere so I don't lose them when I die? I die all the time. My pixel balance hovers around zero as a result. I'm trying to save up for armor but my nonstop deaths are making that difficult.  Is there anywhere I can store my pixels so that when I die, I won't lose a bunch of them? Recover files from hard drive that has been formatted thrice I have a situation.  I got married 6 months ago and stored some very important pictures on my laptop which was running Linux. Later I formatted the whole hard drive, installed Windows and a hacked version of Mac (just to play around) and I have been using the laptop for last 8 months or so after that.  Is there any software that can recover the files for me? I am happy to pay money! What if residuals are normally distributed, but y is not? I've got a weird question. Assume that you have a small sample where the dependent variable that you're going to analyze with a simple linear model is highly left skewed. Thus you assume that $u$ is not normally distributed, because this would result in normally distributed $y$. But when you compute the QQ-Normal plot there is evidence, that the residuals are normally distributed. Thus anyone can assume that the error term is normally distributed, although $y$ is not. So what does it mean, when the error term seems to be normally distributed, but $y$ does not? I recently read this , which stated:     For scientists trying to design a compound that will attach itself to,   and modify, a target disease pathway, the critical first step is to   determine the electronic structure of the molecule. But modeling the   structure of a molecule of an everyday drug such as penicillin, which   has 41 atoms at ground state, requires a classical computer with some   $10^{86}$ bits—more transistors than there are atoms in the observable   universe. Such a machine is a physical impossibility. But for quantum   computers, this type of simulation is well within the realm of   possibility, requiring a processor with 286 quantum bits, or qubits.   Along with this resource estimate for penicillin, I've also seen  of the number of qubits required to model the ground state of caffeine (160 qubits). Given that the above report offers no reference(s) (probably in the name of business intelligence) and much Internet searching and looking into the quantum chemistry literature has come up short, my question is: Where are these resource estimates coming from – is there a journal article that published these numbers? I would really like to identify the methodology and assumptions used in making these estimates.