If I don't err, in the literature a stream cipher is one in which each plaintext bit is processed individually, commonly via xor-ing with one bit of a random or pseudo-random bit stream, while a block cipher (in ECB mode, i.e. ignoring the add-on processing operations like CBC etc.) operates on n bits at a time with operations that are the same for a given key, i.e. each successive groups of n bits are processed in exactly the same manner.  If one looks at the corresponding literatures, one finds in the first case mostly works on linear or non-linear feedback shift registers and in the second case ideas of design of a rather different genre. That could justify the differentiation in terminolgy however IMHO only on the assumption that no cipher designs could lie inbetween the two categories. But that assumption seems to me to be an invalid one. Anyway, let's consider the classical ciphers. Is a Vigenere cipher or a (additive) cipher with a running key a stream cipher or a block cipher? That question seems not to be very satisfactorily to be answered, I am afraid.
I read that     A typical stream cipher encrypts plaintext one byte at a time, although a stream cipher may be designed to operate on one bit at a time or on units larger than a byte at a time.   (Source: , William Stallings.)  A block cipher encrypts one block at a time. The block may be of size one byte or more or less. That means we can also encrypt a block of one byte by help of a stream cipher as a stream.  So, what exactly is the difference between a stream cipher and a block cipher?
$C([0, 1])$ is not complete with respect to the norm $\lVert f\rVert _1 = \int_0^1 \lvert f (x) \rvert \,dx$ In the past, Google Chrome allowed toggling of plugins (like enabling/disabling Flash) from the chrome://plugins URL. This page no longer exists (as of Chrome 57.0.2987.98).   What is the way to access Chrome plugins from this point onwards? Area is calculating wrong using $area in field calculator (QGIS 2.8.1-Wien) In single-blind peer-review, can you reveal your identity without the editor's consent? In my field (chemistry), review is always done in a single blind process, i.e. the author does not know who the referees were, but the referees do know who the authors are. In ten years, I have never seen a referee breaching this anonymity, e.g. by signing their review, unless they got prior approval by the editor (in order to continue discuss things further with the authors, once the manuscript was accepted for publication).  So, it seemed logical to assume that in single blind peer-review, the reviewer should not disclose his identity without the editor's consent. Yet, some people have told me ( and ; also IRL a friend from human sciences) that they have seen people sign their reviews, or write emails to them after the review but before the paper is published.  So, in single-blind peer-review, can you reveal your identity without the editor's consent? Does it depends on the customs of each field, or is there a hard rule? (in which case, the few anecdotes I heard were outliers) Another "can't use Alt. Series Conv. test" (How do I determine if it converges or diverges?) How to include PHP files that require an absolute path? I have a directory structure like the following;     script.php      inc/include1.php   inc/include2.php      objects/object1.php   objects/object2.php      soap/soap.php   Now, I use those objects in both script.php and /soap/soap.php, I could move them, but I want the directory structure like that for a specific reason. When executing script.php the include path is inc/include.php and when executing /soap/soap.php it's ../inc, absolute paths work, /mnt/webdev/[project name]/inc/include1.php... But it's an ugly solution if I ever want to move the directory to a different location.  So is there a way to use relative paths, or a way to programmatically generate the "/mnt/webdev/[project name]/"? Link button in post editor escapes square brackets in code C# Structs: Unassigned local variable? What if I accidentally run command "chmod -R" on system directories (/, /etc, ...) I accidently ran  sudo chmod 755 -R /   instead of  sudo chmod 755 -R ./   I stopped it after few seconds, but now there is some problems such as  sudo: must be setuid root   How can I revert permissions back? Remove empty directory from CVS? I'm not quite sure how this happened, but somehow a completely empty hierarchy of directories has ended up in my repository:  com/ com/companyname/ com/companyname/blah/ com/sun/ com/sun/java/ com/sun/java/jax_rpc_ri/   I think what happened was that these directories did have files in them, but then a developer realized he/she shouldn't have checked them in in the first place since these are by-products of the build process, so he/she removed the files but somehow the empty directories are left in the repository as ancient relics.  How can I remove this from CVS? The only results I seem to be able to find on google say that there shouldn't be a need to remove empty directories as CVS won't keep them around in the first place, and that the -P (prune) options to cvs update should remove them from the working directory  - which is zero help if you actually have empty directories in your repository.  A cvs remove and cvs commit doesn't seem to take care of this situation:  $ cvs remove -Rf com cvs remove: Removing com cvs remove: Removing com/companyname cvs remove: Removing com/companyname/blah cvs remove: Removing com/sun cvs remove: Removing com/sun/java cvs remove: Removing com/sun/java/jax_rpc_ri $ cvs commit com cvs commit: Examining com cvs commit: Examining com/companyname cvs commit: Examining com/companyname/blah cvs commit: Examining com/sun cvs commit: Examining com/sun/java cvs commit: Examining com/sun/java/jax_rpc_ri $ ls -l com total 24 drwxrwxr-x  2 matt matt 4096 Oct 15 14:38 CVS drwxrwxr-x  9 matt matt 4096 Oct 15 14:38 companyname drwxrwxr-x  4 matt matt 4096 Oct 15 14:38 sun   It's still there!  Does SVN have this weird behavior too? Do the Ents go to the Undying Lands? And now I am unable to chmod it back.. or use any of my other system programs. Luckily this is on a VM I've been toying with, but is there any way to resolve this? The system is Ubuntu Server 12.10.   I have attempted to restart into recovery mode, unfortunately now I am unable to boot into the system at all due to permissions not granting some programs after init-bottom availability to run- the system just hangs. This is what I see:  Begin: Running /scripts/init-bottom ... done [   37.062059] init: Failed to spawn friendly-recovery pre-start process: unable to execute: Permission denied [   37.084744]  init: Failed to spawn friendly-recovery post-stop process: unable to execute: Permission denied [   37.101333] init: plymouth main process (220) killed by ABRT signal   After this the computer hangs. How to sum a variable by group What should the character limit(s) for first/last name inputs be? We want to create input fields for a user's first and last names. What should the minimum and maximum limits be, if any, and why? 1970s or 80s kids book: girl's life taken over by a robot doppelganger version of herself I read this book between 1980-82 but it could have been written earlier.  It's about a girl who is dissatisfied with her life, as her parents have her on a diet and she wants to be able to eat what she wants. Someone offers her a solution: to come live in this large building where she can eat all the chocolate eclairs and other junkfood she wants, while a robot doppelganger android version of herself will take her place at home and at school.  The girl agrees, but finds that after week of eating mainly eclairs, she is sick and wants to eat a decent meal. But she is not allowed to eat anything else and has found herself to be a prisoner, so she sets out to get rid of the android and get her life back.   I don't recall the ending but it seemed the 'people' behind it all might have been aliens and the building might have been a kind of ship that then disappears. Dr Math told his family to write 4 different integers from 1 to 9 on to the 4 ] Conditional Expectation of Bernoulli R.V. Let $X_1, X_2,\ldots, X_n$ be iid bernoulli r.v. with parameter $p$. Let $S=X_1+\cdots+X_n$ and $Y=X_1X_2$. Compute $\mathbb{E}(Y\mid S)$.  I know that $\mathbb{E}(X_1\mid S) = S/n$. So If I could split $\mathbb{E}(Y\mid S)$ into two then I would be done. But I don't think that is allowed. How to proceed? I am looking for an easy way to create in Illustrator vintage style corners like on the picture provided.  I have some technical ideas, but they are time consuming, there should be an easier way I believe. How do I resolve "WILL_NOT_PERFORM" MS AD reply when trying to change password in scala w/ the unboundid LDAP SDK? Intersection Number of $B = Y^2 - X^3 + X$ and $F = (X^2 + Y^2)^3 - 4X^2Y^2$ using the fact $I(P,F \cap B) = ord_P^B(F) $.