If we only know the period of a Stream Cipher, let's say 150-200 bit in length, how can we use this information to attack a stream cipher?   Taking a look at this link,  I see that the period of the stream cipher is simply the amount of data we encrypt before starting the encryption over again.   From the attacker's stand point, this let's us know the chunk size of data we are encrypting but how does this help us attack the stream cipher? Won't we still need to know plaintext and cipher text?
My question might appear the same as the question , but actually I did read all the answers and none of them helped me with the details I need.  I am new to cryptography and my problem is with two time pad attacks on OTP. The problem I had in my course was that I have 10 ciphertexts encrypted with the same key $K$. I am then given another ciphertext that I should decrypt.  I know that XOR-ing two ciphers gives me the XOR of their original messages.  My question is what is the correct thing to do after that?  I tried to take 3 ciphertexts $C_1, C_2$ and $C_3$.  Then get $S_1 = C_1 \oplus C_2  \oplus $' ', also get $S_2 = C_1 \oplus C_3 \oplus$ ' '.  After that I compared all corresponding characters in $S_1$ and $S_2$,  and if $S_1[i] = S_2[i]$ then I calculate $S_1[i] \oplus C_2[i]$ to get $K[i]$.  I tried this on paper before coding and it worked, but I might be missing something.  Is this the right approach? Why does it work?
How to retrieve multiple rows from database in PHP Proving the snake lemma without a diagram chase If $f_n$ converges to $f$ in $L^1$ and $g_n$ converges to $g$ in $L^1$. Does it necessarily mean that $f_ng_n$ converges to $fg$ in $L^1$ for finite measure spaces. Is it true that quantum mechanics technically allows anything to happen? Maybe this is a silly question (I think it is), but it's a question I'm arguing with some of my friends for a long time.  The ultimate question is: Is everything (in our Universe) possible ?  I've read some books (Penrose, Hawking, Greene, etc.) where it was clearly stated several times that quantum mechanics allows any situation to happen (e.g. everything is possible) - even with absurdly tiny probabilities?  Does this mean only physically possible - or "ultimate" possible ?  For example (I know this example seems really absurd, but I'm saying this so you get the idea) what my friends clame it is possible:   If I ask my friend(s): "Is it possible there is a Sun-sized star in my pocket right now?" They will respond: "Yes, there is very very tiny possibility this can be true!" Etc. What is this heart in the crimson biome? I found this heart while exploring the crimson biome - what is it? Programmatical Setting of 'Store Relative Pathways' for multiple MXDs ArcGIS 10.1 I am looking to move large number of mxds to a different location on the same drive. Many mxds haven't got 'Store relative pathways' option checked therefore this operation will result in broken links to data. I've only started using ArcGIS 10.1 and it is now possible to programmatically update relative pathways for all mxds by using arcPy and setting relativePaths to be "True". I had a go at writing Python script which (in theory) loops through a top folder and searches for all mxds and then updates "Store relative pathways" setting to be on. When I run this script in PyScripter, it fails to complete, I get the following error:  "exceptions.NameError: name 'mxd' is not defined  Can anyone help ?!? Thanks in advance, Magda      import arcpy, os  folderPath = r"C:\My Folder Path\...\...\..."  for filename in os.listdir(folderPath):     fullpath = os.path.join(folderPath, filename)     if os.path.isfile(fullpath):         basename, extension = os.path.splitext(fullpath)         if extension.lower() == ".mxd":             mxd = arcpy.mapping.MapDocument(fullpath)             mxd.relativePaths = 'True'         mxd.save() del mxd Solvable Lie algebra with codimension 1 ideal There is an exercise in Humphreys's An Introduction to Lie Algebras and Representation Theory: "Any nilpotent Lie algebra contains a codimension 1 ideal".  The proof I am thinking of is the following.  Suppose the Lie algebra $L$ satisfies $L\neq[L,L]$. Then $\pi\colon L\to L/[L,L]$ is a projection onto an abelian algebra. Choose a codimension 1 subspace $I\subset L/[L,L]$. Then $I$ is an ideal and its preimage $\pi^{-1}(I)$ is necessarily an ideal in $L$, because any subspace containing the derived algebra is an ideal. Moreover, $\pi^{-1}(I)$ has codimension 1. $\square$  The only condition on $L$ is that $L\neq[L,L]$, which holds for solvable Lie algebras as well. Is this proof correct? How come Humphreys didn't set the exercise with "nilpotent" replaced by "solvable"? Free way to clone HDD to SSD? Is there a free way to clone a full Windows 7 installation from HDD to SSD? (The free part is important, I know I can pay for Acronis True Image.)      SSDs are usually much smaller than HDDs which complicates matters. For instance, I have about 50GB data, my new SSD is 80GB but I still can't use Windows clone/restore system if my HDD is something like 300GB.  Therefore, I'm looking for a third party tool that will be able to:   Create a clone of my C: partition Store it onto an external USB drive Boot from some rescue / restore CD Load the image onto the new SSD   Acronis True Image seems like a tool that should support this but it's a paid-for software and the trial version cannot create clones. Acronis Migrate Easy is a fully functional tria for 15 days but need both the HDD and SSD connected at the same time which is a bit of a problem for me as a laptop user.  P.S. I almost got there combining Windows image backup combined with Acronis True Image restore CD (which can load .vhd's) but was not able to boot as some boot information were probably lost and could not be repaired using the Win7 installation DVD. Does this parallel structure need coordinated prepositions to avoid being a faulty parallelism? How can I create a custom terminal command (to run a script)? I'm studying machine learning and every book I open I bump into chi-squared distribution, gamma-function, t-distribution, Gaussian, etc.   Every book I have opened so far only defines what the distributions are: they don't explain or give the intuition on where the specific formulas for the functions come from.   For example, why is chi-squared distribution the way it is? What is the t-distribution? What is the intuition behind the distribution? Proofs? etc.   I would like to have a clear and fundamental understanding of the most commonly used distributions so that every time later on when I see them, I truly understand what is a t-distribution, what is a Gaussian distribution and most importantly why are they the way they are.   It would be nice if the books / tutorials  can explain the concepts to a layman so that in order to understand them you don't already need to understand them x) Many books are like this, they don't fit for beginners :( Unicode error in inputenc package Why did the Resistance automatically assume the use of this tech in The Last Jedi? FaceTime not working on iPhone 6 Plus purchased from Dubai I bought my iPhone 6 Plus in Dubai. I am using the phone in Sri Lanka and I cannot use the FaceTime. How can I use FaceTime while in Sri Lanka? Who uses Dual_EC_DRBG? Recent news articles have suggested that the NSA may be involved in trying to influence the cryptography in public standards or commercially deployed software, to enable the NSA to decrypt the encrypted traffic.  For example, .  The New York Times article specifically mentions a 2006 NIST standard, where two Microsoft engineers later discovered a serious problem in the scheme.  The New York Times article explains how the standard was written by the NSA, who pushed the scheme hard:     Simultaneously, the N.S.A. has been deliberately weakening the international encryption standards adopted by developers. One goal in the agency’s 2013 budget request was to “influence policies, standards and specifications for commercial public key technologies,” the most common encryption method.      Cryptographers have long suspected that the agency planted vulnerabilities in a standard adopted in 2006 by the National Institute of Standards and Technology, the United States’ encryption standards body, and later by the International Organization for Standardization, which has 163 countries as members.      Classified N.S.A. memos appear to confirm that the fatal weakness, discovered by two Microsoft cryptographers in 2007, was engineered by the agency. The N.S.A. wrote the standard and aggressively pushed it on the international group, privately calling the effort “a challenge in finesse.”    After some sleuthing, I'm pretty certain this is a reference to the  pseudorandom number generator scheme described in NIST SP 800-90.  The weakness is that Dual_EC_DRBG appears to contain a backdoor, and anyone who knows the backdoor can totally break the PRNG.  The weakness was first described in  and was subsequently .  As a consequence, there are now good reasons to suspect that Dual_EC_DRBG contains a NSA backdoor, and the NSA might be able to spy on anyone who is using Dual_EC_DRBG.  My questions:   Who uses Dual_EC_DRBG? Do any commercial products use Dual_EC_DRBG? Does anyone use it? Can we please move the  "Start a bounty" link to be in the same location as all of the other action buttons? It makes no sense to me for this to be buried after the comments - It's an action on the Question. It can be very difficult to locate, especially when your question gets .  I don't think this should be that difficult to implement - it's just moving the location of a design element. Can we please get this button moved? How can I find just the *.mp3 files with a recursive command like ls -R *.mp3 in a directory that contains several sub-directories and at the end copy these files in a directory that I choose.  Thanks for your support. DML is not allowed in a constructor. Is there a known reason behind this limit?  I have been searching for the answer &amp; haven't found anything which addresses the question. May be it's not documented anywhere(Or google doesn't know where it is). Show that $f(z) = cg(z)$ is valid for two analytic functions $f$ and $g$ given a certain relationship between them How to disable a USB port in Windows (XP) and make it available only for charging?