We know that  is generally a one-way function where we can't retrieve the original message. On the other hand, encryption is a two-way-function where we get the original message from the encrypted message or vice versa. So, in a normal sense, we can't use hash function to construct an encryption algorithm.  What I want to know is, if it’s theoretically possible to somehow create an encryption algorithm using a hash function, or if any encryption algorithm uses hash function in any part of their algorithm?
Say I have an embedded device which is only capable of doing HMAC-SHA1 transformations (that device is, in fact, a YubiKey).  Would it be secure to feed it like a block cipher in counter mode to get a random pad suitable as an stream cipher?  Of course, I'm talking about not repeating the counter value ever to encrypt data (so this construction would also need some random IV or treating the counter value as a nonce forever).
I'm using the word "Zwei-Drittel-Abstimmungsmehrheit" a bunch of times in my document. Often it won't fit into the current line, extending into the right margin.  I figured out that the following package helps :  \usepackage[shortcuts]{extdash}    Then I can write  Zwei\-/-Drittel\-/Abstimmungs\-mehrheit   and the hyphenation is done correctly.  Is there a way that I can set this hyphenation globally for this word? Like i can do it with the command  \hyphenation{...}   Sadly this command doesn't work for words containing dashes. Is there any way to automatically get notified of property changes in a class without having to write OnPropertyChanged in every setter?  (I have hundreds of properties that I want to know if they have changed).    Anton suggests .  I've actually used the "Castle" library for something similar in the past, and while it does reduce the amount of code I've had to write, it added around 30 seconds to my program startup time (ymmv) - because it's a runtime solution.  I'm wondering if there is a compile time solution, maybe using compile-time attributes...    Slashene and TcKs give suggestions which generates repetitive code - unfortunately, not all my properties are a simple case of m_Value = value - lots of them have custom code in the setters, so cookie-cutter code from snippets and xml aren't really feasible for my project either. Is it true that $A^A\simeq P(A)$? Let $A$ be an infinite set and $$A^A=\{f | f:A\to A\,\,\, \text{is a function}\}.$$ Is there any natural bijection between $A^A$ and $P(A)$? I know that each new tab on Google Chrome have its own process, but I have 14 chrome.exe processes running actually as I can see it on the Task Manager, and only two tabs are opened on Google Chrome.    Could it be due to Chrome extensions? What other reason can open more chrome.exe process and how to avoid it? What is the difference between a predicate and function? I need to to understand the difference between predicates and functions in the context of Clasual Form Logic in order to define the Herbrand universe.  If I have p(x) :- q(f(x)) would I be right in saying that p and q are predicates while f is a function because it is "nested"?  By this thinking then if I have p(x) :- q(x) both p and q are predicates and I have no functions?  If this is incorrect then how can I tell the difference between a predicate and function? Differentiation - simple case Fedora 14 uses vi by default when one runs visudo. Is there a way to change this to something else? shopt works in command line, not found when run in a script I'm writing a script to copy some files around, and trying to use shopt -s dotglob  like .jshint and whatnot.    I can run shopt -s dotglob directly at a bash prompt with no error.  However, running the script throws the error:  script.sh: 81: script.sh: shopt: not found   I'm running this script in bash shell, with the shebang header #!/usr/bin/env bash.  Error line:  shopt -s dotglob cp -r $TEMP/img/* $TARGET/img/ cp -r $TEMP/js/* $TARGET/js/ cp -r $TEMP/less/* $TARGET/less/   Not finding anything helpful on google, any idea what the problem is here? I have just had my broadband upgraded to  which means my router has had to change. Previously I was using a Thomson TG585v7 ADSL thingy provided by my ISP. One nice thing about that router was that it would act as a local DNS and allow me to find my other machines on the network by using &lt;hostname&gt;.lan instead of IP addresses.  I've now switched to a Linksys WRT320N ethernet router which connects to my fibre modem, and which I've updated to the latest firmware (1.0.04). I have 2 machines on the network which I regularly want to connect to each other; one is running Windows 7 and the other is running OS X Lion.  The problem I'm having is that I'm unable to connect to my Win7 machine from the OS X machine using the Win7 machine's name. However, I'm able to ping the OS X machine from my Win7 machine using the hostname. power outage/frozen meat We were on vacation for a week. The neighbor said we were out of power the whole time.  We have a chest freezer full of beef. It thawed but remained in the freezer unopened the whole time. Is the meat bad if it is thawed but still cold? Can we refreeze it and eat it? What is the best prepaid SIM card for data in France? I'm going to travel to Paris in two weeks for 5 days. I'd like to buy a prepaid SIM card for my phone, no calls or SMS needed - only data is sufficient. I've looked through French mobile operators and found nothing really acceptable. For example, in Finland I bought SIM card for €5 with 3GB of data.   So, the question is - what is the best SIM card for me, assuming that 1GB is enough (considering the prices) and that I am actually will be able to use it (I've read that some operators turn on mobile data only after 5 days which is unacceptable for me considering that I'll be there for 5 days only)? Proving a Composition of Functions is Bijective If I have $f:\mathbb{R}\rightarrow\mathbb{R}$ such that $f$ is onto and $f\circ f\circ f = f$, how can I prove that $f$ is bijective? I know that I only have to prove that it is 1-to-1 because I'm given the fact that it's onto, but how can I use the fact that $f\circ f\circ f=f$ to prove that it is 1-to-1?  Thanks! Search only for the currently active language Opacity of background-color, but not the text How do I make the cross-browser (including Internet Explorer 6) transparency for the background of a div while the text remains opaque?  I need to do it without using any library such as jQuery, etc. (But if you know of a library that does it I'd love to know so I can look at their code). independent variables in Random forest model Question mark and colon in JavaScript What is considered a "real question"? Note:   This close reason is old and only applies to old questions that were closed prior to the closing overhaul. This has been replaced by the reasons "unclear what you're asking" for unclear questions and "too broad" for overly broad questions. Older questions that have been closed as "not a real question" will remain closed under this reason, so this question is left here for reference.   Questions used to be closed as "not a real question."     What makes a question a "real" question? What are new users expected to know about asking "real" questions? Why does SE treat questions differently from other online forums? We have a org wide email addressed which has been "Verified" into our sandbox. I understant org wide email addressed is unsupported metadata, so this was achieved as pre deployment step.   Into our repo, we have a workflow that send email alert to that org wide email address. "  Workflow   ... &lt;senderAddress&gt;noreply@mycompany.com.au&lt;/senderAddress&gt; &lt;senderType&gt;OrgWideEmailAddress&lt;/senderType&gt;    The problem we are facing is that we are still getting the following error even if this org wide email address is verified:      You must specify a verified Org Wide Email Address for this sender   type.   Is that a bug in the metadata api or expected behaviour ? Ideally we would like to not have to do that as a post deployment step.   PS: We are running DX under api version 43.0 Copying applications from applications folder to external and reinstalling osx Is it possible to copy all my applications from the applications folder onto an external, format my mac, reinstall OS X and finally copy the applications back into the applications folder for installing them?  Will that work? I am asking because my macbook seems to be behaving in a very odd manner, has become excessively sluggish and is preventing me from recording anything in logic.. I have tried the usual freeing up space, clean desktop, fixing permissions, verifying and repairing disk as well as resetting pram and making sure I have all the latest software and firmware updates. The macbook is only 8 months old and is running Lion with 8gb of ram, I really cannot understand what is wrong with it. Even when trying to watch a movie, the player will get serious audio/video synchronisation issues and I noticed that every time my wifi is on the fans speed up like a plane taking off. I even checked and it is clean from any dust. I am perplexed :(   If anyone could help me please, I would greatly appreciate it.  Thanks in advance! What is the difference between below variables assignments?   var=23 var =23 var= 23 var = 23   Is there any difference in space around the assignment operator?