Example of a Hash function which is second pre-image resistant but not collision resistant
Are there attacks that break collision resistance but not preimage resistance?
I'm looking for a word which indicates that a person has adopted a quality suggested by their name, e.g. a person named Grace who is indeed graceful, or perhaps someone named Shepherd who has become a shepherd.  I have a strong notion that I once learned such a word, but I have forgotten it and have never re-discovered it. Curve Bevel function, scale? Renaming files in lexicographical order with a numerical pattern that increases sequentially with fixed padding I have files such as  a bb ccc abc emrls   I would like to rename them so that, after sorting them (for example, lexicographically), each file gets the following name:  00001 00002 00003 etc   where the # of digits for the 0 padding is specified a priori, e.g. 6 in the case above (assuming that we know how many digits are needed).  Since the shell I am most comfortable with is zsh, I'm interested in solutions that benefit from features on zsh (maybe using zsh's zmv?). I would also be interested in solutions that are compatible with Bash. If a two vectors $\bf u$ and $\bf v$ in linearly independent, can their images be linearly dependent given they were transformed by a linear transformation $T$? I think not. My reasoning If the images are linearly dependent, then $c_1T({\bf u})+c_2T({\bf v})={\bf 0}$ for scalars $c_1$ and $c_2$, not both $0$. Then $c_1T({\bf u})+c_2T({\bf v})={\bf 0}$ $T(c_1{\bf u}+c_2{\bf v})=T({\bf 0})$ $c_1{\bf u}+c_2{\bf v}={\bf 0}$ Therefore, ${\bf u}$ and $\bf v$ are linearly dependent. My reservation A homework problem seems to contradict the above. Here's the problem: Let $\mathbb R^n\rightarrow\mathbb R^m$ be a linear transformation. Suppose $\{{\bf u},{\bf v}\}$ is a linearly independent set, but $\{T({\bf u}),T({\bf v}\})$ is a linearly dependent set. Show that $T({\bf x})={\bf 0}$ has a nontrivial solution. How do I bake/add material colors onto my UVmap? I looked everywhere from tutorials to documents and either they only talk about texturing or they are doing the tutorial in 'blender render' when I need it in 'cycles render'.   I have a cube that is toon shaded red. And as you can see it is unwrapped to show the map.    Now I would like to add the color that's on the cube onto the map.   As you can see at the bottom of the image that I created a new image called 'untitled'. Now the next step of baking the colors onto the map is where I become lost. Regardless of which 'Bake Type' that I used, I keep getting error messages like: No valid selected objects.  Everything looks selected to me. No, I am not new to Blender but I am new to color baking. Thank you for any help provided; I used a simple cube first before using other models I already created. We have officially discontinued the Amazon book affiliate remnant ads, since despite our best efforts they don't perform well for our audience and cannot be made to perform well.  We've often wondered,   I'm thinking this isn't a problem; it has gotten lots of support historically. So we're going to go ahead and do it, so the company Amazon account is still getting some use, and we benefit a little.   To be clear: from this point on, all Amazon links posted on all sites will automatically be rewritten to add our affiliate link. We have a clever affiliate redirect that geolocates the IP address and redirects to the appropriate regional Amazon store (amazon.uk, amazon.ca, et cetera).  If you have any feedback on this, or suggestions, as they say &hellip; speak now or forever hold your peace! How can you construct the bijection between real numbers and functions over naturals? How to export / dump a MySql table into a text file including the field names (aka headers or column names) Were I rich, I would live on Long Island.   If I were rich, I would live on Long Island.   Is the first sentence still used, or is used in particular contexts (in example, to give emphasis to the sentence)? Problem  I have various footnotes, which are hyperlinked from the text to the bottom of their respective pages. When I click on the hyperlinks (in the main text), they always take me to the first page of my document. I also have footnotebackref which puts a hyperlink at the footnote to take the reader back to the main body of text and these links for fine.   Edited MWE  After a lot of deletion, I have managed to reduce the document to the following lines. One might say that I have found the problem, since the removal of \usepackage[hang, flushmargin]{footmisc} stops the problem, but I would still like to have non-indented footnotes.  \documentclass{article}  \usepackage[usenames,dvipsnames]{color} \usepackage[colorlinks=true]{hyperref}  \usepackage[hang, flushmargin]{footmisc}         %Problem line. \usepackage{footnotebackref}  \begin{document} \tableofcontents             \newpage                 \section{Section} This is some text\footnote{This is a footnote.}. \end{document} This is problem #6 from Section 1.2 of Ash's Real Variables With Basic Metric Space Topology.   I am asked to show that it is impossible to list the rational numbers in increasing order.   While I know it is possible to list a finite subset of the rational numbers in increasing order, I was wondering if the reason for the impossibility in this case is because there is no least element of $\mathbb{Q}$?   I mean, it's possible to impose an ordering on $\mathbb{Q}$ (correct me if I'm wrong, but it seems possible to compare any two rationals).  But the set $\mathbb{Q}$ is of course, a subset of itself, and the Well-Ordering Principle says that a set $S$ is Well-Ordered only if any subset of $S$ contains a minimal element. Since $\mathbb{Q}$ does not contain a minimal element, it does not appear that it is a Well-Ordered set.   Is this the correct idea as to why it's impossible? If not, could somebody explain to me what the correct idea is and a strategy for proving it?  Thank you ahead of time. Consider a hypothetical situation: In which a time traveler travels in a spaceplane at close to speed of light circling the earth and I get a live telecast of inside of that plane to my television. How time dilation will effect him and what will I observe sitting next to the tv seeing him live. Considering time runs slower at speed of light, will he be looking like a slow motion video? (Or let he also watching live streaming of us at earth, what it will look to him) P.S. I'm not sure if it even makes some sense but if it does kindly explain in logical details. Sorry for the the bad english, I'm not a native speaker. Impose strict time-limit for questions on Hot Network Questions list I tried getting a good measurement with my caliper, but the flexibility of the tire doesn't help much. Let's say I have a 26&quot;x2.125&quot; tire. I know this fits on an ISO 559mm bead seat diameter rim, and 26&quot; = 660.4mm. 26&quot;:  The OD of the tire including the tread? The OD of the tire excluding the tread? When aired up or deflated? Means it fits a 559mm ISO BSD None of the above?  2.125&quot;:  Width of tread? Width of sidewall? Inflated or deflated?  Essentially, I'm converting the tire sizes to &quot;height off rim in mm&quot; and drawing them with a wheel in a web application, so I need to know how &quot;tire size&quot; translates to this measurement. I'm somewhat assuming that the fractional sizes can be converted to the same measurement, but I'm aware that they have certain differences - so any help there would be of value as well.  has been helpful, but still leaves me with the questions above. How do you convert a number to a string showing dollars and cents?  eg: 123.45    =&gt; '$123.45' 123.456   =&gt; '$123.46' 123       =&gt; '$123.00' .13       =&gt; '$0.13' .1        =&gt; '$0.10' 0         =&gt; '$0.00' Why does a cork float to the side of a glass? Why does a cork ball float to the side of a glass as illustrated in the following GIF? What is the physical phenomenon behind this observation and why does it happen? Why so many files in /usr/share/app-install/desktop? For 14.04, I'm trying out Lubuntu LTS.  If I run ls -l /usr/share/app-install/desktop, I get a list of 3085 .desktop files. All except one are dated Apr 18. The exception is:  -rw-r--r-- 1 root root  6328 Mar 28  2013 applications.menu   From the dates, it's clear that all these are installed by default and not by me.   Doesn't each GUI-based program bring in its own .desktop file at the time it's installed (mostly in /usr/share/applications)? Then why are these thousands of other .desktop files needed? From their names, most of them haven't anything to do with Lubuntu. Their names are different from regular .desktop files (such as those in /usr/share/applications): many, not all, are like name:name.desktop whereas the regular ones are just name.desktop. The ones I looked at all have a line with X-AppInstall-Popcon=nnn where nnn is a string of digits. I know that Popcon "gathers statistics determining which packages are the most popular with Ubuntu users". But why is that part of these .desktop files? $ df -kh Filesystem      Size  Used Avail Use% Mounted on udev            7,8G     0  7,8G   0% /dev tmpfs           1,6G   19M  1,6G   2% /run /dev/sda2       622G  227G  364G  39% / tmpfs           7,8G  1,1G  6,7G  14% /dev/shm tmpfs           5,0M  4,0K  5,0M   1% /run/lock tmpfs           7,8G     0  7,8G   0% /sys/fs/cgroup /dev/loop1      143M  143M     0 100% /snap/inkscape/2527 /dev/loop3       79M   79M     0 100% /snap/core/1441 /dev/loop0       79M   79M     0 100% /snap/core/1577 /dev/loop4       79M   79M     0 100% /snap/core/1512 /dev/loop2       62M   62M     0 100% /snap/pencilsheep/5 tmpfs           1,6G   92K  1,6G   1% /run/user/1000   What are these /dev/loop device files? My RAM is always full. Is this related? Method for batch layout of images into PDF sheets I have 100,000 identically-sized, but unique, PNG/JPG images which I want to automatically layout onto A4 sheets which can then be exported as print-ready PDFs.  So assuming I can fit 8 of these images per page in a 4x2 grid, I'm looking to input my 100,000 images and output 12,500 PDFs.  I'm a programmer so I could probably write a script to do this myself (e.g. PHP/Python), but I was wondering whether there are any tools/scripts/software that already exists that can do this automatically. Bizarre spacing with 4 $\star$s