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• Simple string encryption in .NET and Javascript

  - by jonathanconway

  I'm developing an ASP.NET MVC application in which I want to encrypt a short string on the server, using C#, and send it to the client-side. Then on the client-side it will be decrypted through Javascript code. Any thoughts on how to implement this? Do you know of a simple encryption algorithm (doesn't have to be bullet-proof secure) that can be easily translated from C# to Javascript or vice-versa? NOTE: I could do this entirely in C# and do the decryption through Ajax, but I'd prefer not to do it this way, as I want to reduce website traffic as much as possible.

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• Interpolating 1D Gaussian into 2D Gaussian

  - by Drazick

  Let's say I have a 1D Gaussian function. Its length is 600 for that matter. I want to Interpolate it into 2D Gaussian of the size 600 X 600. This is the code I wrote (OTFx is the Gaussian Function, OTF - 2d Interpolated Function): [x, y] = meshgrid([-300:299], [-300:299]); r = sqrt((x .^ 2) + (y .^ 2)); OTF = interp1([-300:299], OTFx, r(:), 'spline'); OTF = reshape(OTF, [600, 600]); The problem is I get Overshoot at the end: How can I prevent it? Is there better Interpolating algorithm for Monotonic Descending Functions?

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• Security & Authentication: SSL vs SASL

  - by 4herpsand7derpsago

  My understanding is that SSL combines an encryption algorithm (like AES, DES, etc.) with akey exchange method (like Diffier-Hellman) to provide secure encryption and identification services between two endpoints on an un-secure network (like the Internet). My understanding is that SASL is an MD5/Kerberos protocol that pretty much does the same thing. So my question: what are the pros/cons to choosing both and what scenarios make both more preferable? Basically, I'm looking for a guidelines to follow when choosing SSL or to go with SASL instead. Thanks in advance!

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• Calculating Divergent Paths on Subtending Rings

  - by Russ

  I need to calculate two paths from A to B in the following graph, with the constraint that the paths can't share any edges: hmm, okay, can't post images, here's a link. All edges have positive weights; for this example I think we can assume that they're equal. My naive approach is to use Djikstra's algorithm to calculate the first path, shown in the second graph in the above image. Then I remove the edges from the graph and try to calculate the second path, which fails. Is there a variation of Djikstra, Bellman-Ford (or anything else) that will calculate the paths shown in the third diagram above? (Without special knowledge and removal of the subtending link, is what I mean)

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• How to create a custom ADO Multi Demensional Catalog with no database

  - by Alan Clark

  Does anyone know of an example of how to dynamically define and build ADO MD (ActiveX Data Objects Multidimensional) catalogs and cube definitions with a set of data other than a database? Background: we have a huge amount of data in our application that we export to a database and then query using the usual SQL joins, groups, sums etc to produce reports. The data in the application is originally in objects and arrays. The problem is the amount of data is so large the export can take 2 hours. So I am trying to figure out a good way of querying the objects in memory, either by a custom OLAP algorithm or library, or ADO MD. But I haven't been able to find an example of using ADO MD without a database behind it. We are using Delphi 2010 so would use ADO ActiveX but I imagine the ADO.NET MD is similar. I realize that if the application data was already stored in a database the problem would solve itself. Also if Delphi had LINQ capability I could query the objects and arrays that way.

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• SQLAlchemy custom sorting algorithms when using SQL indexes

  - by David M

  Is it possible to write custom collation functions with indexes in SQLAlchemy? SQLite for example allows specifying the sorting function at a C level as sqlite3_create_collation(). An implementation of some of the Unicode collation algorithm has been provided by James Tauber here, which for example sorts all the "a"'s close together whether they have accents on them or not. Other examples of why this might be useful is for different alphabet orders (languages other than English) and sorting numeric values (sorting 10 after 9 rather than codepoint order.) Is this possible in SQLAlchemy? If not, is it supported by the pysqlite3 or MySQLdb modules, or for any other SQL database modules supported by python for that matter? Any information would be greatly appreciated.

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• what does this C++ line of code mean "sol<?=f((1<<n)-1,i,0)+abs(P[i])*price;"

  - by KItis

  Could anyone help me to understand following line of code. sol I am studying an algorithm written using c++ and it has following operator " following is the error message returned. Hello.cpp: In function ‘int main()’: Hello.cpp:115: error: ‘memset’ was not declared in this scope Hello.cpp:142: error: expected primary-expression before ‘?’ token Hello.cpp:142: error: expected primary-expression before ‘=’ token Hello.cpp:142: error: expected ‘:’ before ‘;’ token Hello.cpp:142: error: expected primary-expression before ‘;’ token may be " Thanks in advance for the time you spent reading this post.

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• Prevent Method call without Exception using @PreAuthorize Annotation

  - by Chepech

  Hi all. We are using Spring Security 3. We have a custom implementation of PermissionEvaluator that has this complex algorithm to grant or deny access at method level on the application. To do that we add a @PreAuthorize annotation to the method we want to protect (obviously). Everything is fine on that. However the behavior that we are looking for is that if a hasPermission call is denied, the protected method call only needs to be skipped, instead we are getting a 403 error each time that happens. Any ideas how to prevent that? You can find a different explanation of the problem here; AccessDeniedException handling during methodSecurityInterception

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• In Haskell, how can you sort a list of infinite lists of strings?

  - by HaskellNoob

  So basically, if I have a (finite or infinite) list of (finite or infinite) lists of strings, is it possible to sort the list by length first and then by lexicographic order, excluding duplicates? A sample input/output would be: Input: [["a", "b",...], ["a", "aa", "aaa"], ["b", "bb", "bbb",...], ...] Output: ["a", "b", "aa", "bb", "aaa", "bbb", ...] I know that the input list is not a valid haskell expression but suppose that there is an input like that. I tried using merge algorithm but it tends to hang on the inputs that I give it. Can somebody explain and show a decent sorting function that can do this? If there isn't any function like that, can you explain why? In case somebody didn't understand what I meant by the sorting order, I meant that shortest length strings are sorted first AND if one or more strings are of same length then they are sorted using < operator. Thanks!

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• Candidate Elimination Question---Please help!

  - by leon

  Hi , I am doing a question on Candidate Elimination Algorithm. I am a little confused with the general boundary G. Here is an example, I got G and S to the fourth case, but I am not sure with the last case. Sunny,Warm,Normal,Strong,Warm,Same,EnjoySport=yes Sunny,Warm,High,Strong,Warm,Same,EnjoySport=yes Rainy,Cold,High,Strong,Warm,Change,EnjoySport=no Sunny,Warm,High,Strong,Cool,Change,EnjoySport=yes Sunny,Warm,Normal,Weak,Warm,Same,EnjoySport=no What I have here is : S 0 :{0,0,0,0,0,0} S 1 :{Sunny,Warm,Normal,Strong,Warm,Same} S 2 , S 3 : {Sunny,Warm,?,Strong,Warm,Same} S 4 :{Sunny,Warm,?,Strong,?,?} G 4 :{Sunny,?,?,?,?,?,?,Warm,?,?,?,?} G 3 :{Sunny,?,?,?,?,?,?,Warm,?,?,?,?,?,?,?,?,?,Same} G 0 , G 1 , G 2 : {?,?,?,?,?,?} What would be the result of G5? Is it G5 empty? {}? or {???Strong??) ? Thanks

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• GA written in Java

  - by EnderMB

  I am attempting to write a Genetic Algorithm based on techniques I had picked up from the book "AI Techniques for Game Programmers" that uses a binary encoding and fitness proportionate selection (also known as roulette wheel selection) on the genes of the population that are randomly generated within the program in a two-dimensional array. I recently came across a piece of pseudocode and have tried to implement it, but have come across some problems with the specifics of what I need to be doing. I've checked a number of books and some open-source code and am still struggling to progress. I understand that I have to get the sum of the total fitness of the population, pick a random number between the sum and zero, then if the number is greater than the parents to overwrite it, but I am struggling with the implementation of these ideas. Any help in the implementation of these ideas would be very much appreciated as my Java is rusty.

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• What does 'salt' refer to in string-to-key (s2k) specifier?

  - by WilliamKF

  What does 'salt' refer to in string-to-key (s2k) specifier? It appears to be a random number generator to shake things up, but I would like to know what 'salt' stands for? For example it is written: 3.6.1.2. Salted S2K This includes a "salt" value in the S2K specifier -- some arbitrary data -- that gets hashed along with the passphrase string, to help prevent dictionary attacks. Octet 0: 0x01 Octet 1: hash algorithm Octets 2-9: 8-octet salt value Salted S2K is exactly like Simple S2K, except that the input to the hash function(s) consists of the 8 octets of salt from the S2K specifier, followed by the passphrase. But salt is not defined, although its meaning seems clear.

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• Finding if a path between 2 sides of a game board exists

  - by Meny

  Hi, i'm currently working on a game as an assignment for school in java. the game cuurently is designed for Console. the game is for 2 players, one attacking from north to south, and the other from west to east. the purpose of the game is to build a "bridge"/"path" between the 2 of your sides before your opponent does. for example: A B C D E F 1 _ _ X _ _ _ 1 2 O X X _ _ _ 2 3 O X O O O O 3 4 O X O _ _ _ 4 5 X X _ _ _ _ 5 6 X O _ _ _ _ 6 A B C D E F player that attacks from north to south won (path/bridge from C to A) my problem is, what algorithm would be good to check if the user have managed to create a path (will be checked at the end of each turn). you're help would be very appreciated.

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• Document ranking strategy for P2P file sharing system.

  - by ablmf

  Recently, I got a task of building a P2P file sharing system. There is one requirement : the system should have a document ranking algorithm so that it could be used help users find more valuable files. Several strategy might be useful : force user to give a score to a file before it was downloaded The documents containing certain key words would get higher rank Manager could modify file ranking manually the more a file was downloaded, it would get a higher rank. Do you know any other strategy or methods that also appropriate? Or is there any real world example?

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• How to generate a random alpha-numeric string in Java

  - by Todd

  I've been looking for a simple java algorithm to generate a pseudo-random alpha-numeric string. In my situation it would be used as a unique session/key identifier that would "likely" be unique over 500K+ generation (my needs don't really require anything much more sophisticated) . Ideally I would be able to specify a length depending on my uniqueness needs. For example, a generated string of length 12 might look something like "AEYGF7K0DM1X". Answers: I like @Apocalisp and @erickson's answers equally well. The only downside to @Apocalisp's answer is it requires an apache class. Thanks to both for the help!

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• SQL Encryption - Asymmetric Key - 2nd Server

  - by Jason Heine

  Hello, I created an asymmetric key on one of my SQL servers (2008). I encrypted a password field and I am able to retrieve that password just fine on my development server. The issue comes into play where I need to move this data to a production server. Here is the code for the key that was created: CREATE MASTER KEY ENCRYPTION BY PASSWORD='#########' CREATE ASYMMETRIC KEY UserEncryptionKey WITH ALGORITHM = RSA_2048 Now, when I run this on the production server, it creates the key just fine. However, when I run my sproc to get the password, it returns NULL. SQL: SELECT EncryptByAsymKey(AsymKey_ID('UserEncryptionKey'), Password ) FROM Users WHERE UserName = '######' Any thoughts on what I need to do to get the encrypted field to work on multiple SQL Servers? Please let me know if I need to clarify something. Thanks

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• Embarrassingly parallel workflow creates too many output files

  - by Hooked

  On a Linux cluster I run many (N > 10^6) independent computations. Each computation takes only a few minutes and the output is a handful of lines. When N was small I was able to store each result in a separate file to be parsed later. With large N however, I find that I am wasting storage space (for the file creation) and simple commands like ls require extra care due to internal limits of bash: -bash: /bin/ls: Argument list too long. Each computation is required to run through a qsub scheduling algorithm so I am unable to create a master program which simply aggregates the output data to a single file. The simple solution of appending to a single fails when two programs finish at the same time and interleave their output. I have no admin access to the cluster, so installing a system-wide database is not an option. How can I collate the output data from embarrassingly parallel computation before it gets unmanageable?

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• Drawing bezier curve with limited subdivisions in OpenGL

  - by xEnOn

  Is it possible to tell OpenGL to draw a 4 degree (5 control points) bezier curve with 10 subdivisions? I was trying with this: point ctrlpts[] = {..., ..., ..., ...}; glMap1f(GL_MAP1_VERTEX_3, 0, 1, 3, 5, ctrlpts); glBegin(GL_LINE_STRIP); for (i = 0; i <= 30; i++) glEvalCoord1f((GLfloat) i/30.0); glEnd(); But this just draws the curve nicely. I am thinking that I want the algorithm inside the bezier curve to draw only until 10 subdivisions and then stop. The line should look a little facet.

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• how to compare/validate sql schema

  - by Ron Harlev

  I'm looking for a way to validate the SQL schema on a production DB after updating an application version. If the application does not match the DB schema version, there should be a way to warn the user and list the changes needed. Is there a tool or a framework (to use programatically) with built-in features to do that? Or is there some simple algorithm to run this comparison? Update: Red gate lists "from $395". Anything free? Or more foolproof than just keeping the version number?

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• Google Web Optimizer -- How long until winning combination?

  - by Django Reinhardt

  I've had an A/B Test running in Google Web Optimizer for six weeks now, and there's still no end in sight. Google is still saying: "We have not gathered enough data yet to show any significant results. When we collect more data we should be able to show you a winning combination." Is there any way of telling how close Google is to making up its mind? (Does anyone know what algorithm does it use to decide if there's been any "high confidence winners"?) According to the Google help documentation: Sometimes we simply need more data to be able to reach a level of high confidence. A tested combination typically needs around 200 conversions for us to judge its performance with certainty. But all of our conversions have over 200 conversations at the moment: 230 / 4061 (Original) 223 / 3937 (Variation 1) 205 / 3984 (Variation 2) 205 / 4007 (Variation 3) How much longer is it going to have to run?? Thanks for any help.

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• Python or matplotlib limitation error

  - by Werner

  Hi, I wrote an algorithm using python and matplotlib that generates histograms from some text input data. When the number of data input is approx. greater than 15000, I get in the (append) line of my code: mydata = [] for i in range(len(data)): mydata.append(string.atof(data[i])) the error: Traceback (most recent call last): File "get_histogram_picture.py", line 25, in <module> mydata.append(string.atof(data[i])) File "/usr/lib/python2.6/string.py", line 388, in atof return _float(s) ValueError: invalid literal for float(): -a can it be an error in python ? What is the solution ? Thanks

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• extract data from an array without using loop in R

  - by Manolo

  I have a vector v with row positions: v<-c(10,3,100,50,...) with those positions I want to extract elements of a matrix, having a column fixed, for example lets suppose my column number is 2, so I am doing: data<-c() data<-c(matrix[[v]][[2]]) matrix has the data in the following format: [[34]] [1] "200_s_at" "4853" "1910" "3554" "2658" So for example, I want to extract from the row 342 the value 1910 only, column 2, and do the same with the next rows but I got an error when I want to do that, is it possible to do it directly? or should I have a loop that read one by one the positions in v and fill the data vector like: #algorithm for i<-1 to length(v) pos<-v[i] data[[i]]<-c(matriz[[pos]][[2]]) next i Thanks

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• Is there a sample set of web log data available for testing analysis against?

  - by Peter

  Sorry if this isn't strictly speaking a programming question, but I figure my best chance of success would be to ask here. I'm developing some web log file analysis algorithms, but to date I only have access to a fairly small amount of web log data to process. One algorithm I want to use makes some assumptions about 'the shape' of typical web log data, and so I'd like to test it against a larger 'exemplar' - perhaps the logs of a busy site with a good distribution of traffic from different sources etc. Is there a set of such data available somewhere? Thanks for any help.

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• pgp key information

  - by calccrypto

  can someone show a description of the information of what a pgp looks like if only the descriptions were there but not the actual information? something like (i dont remember if the values are correct): packet-type[4 bits], total length in bytes[16 bits], packet version type [4 bits], creation-time[32 bits], encryption-algorithm[8 bits], ...,etc,etc ive tried to understand rfc4880, but its tedious and confusing. so far, i am think i have extracted the 4 i wrote above, but i cant seem to get the rest of the information out. can anyone help? i know i can just find some pgp program, but the whole point of this is to allow me to learn how those programs work in the first place

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• Why does my program occasionally segfault when out of memory rather than throwing std::bad_alloc?

  - by Bradford Larsen

  I have a program that implements several heuristic search algorithms and several domains, designed to experimentally evaluate the various algorithms. The program is written in C++, built using the GNU toolchain, and run on a 64-bit Ubuntu system. When I run my experiments, I use bash's ulimit command to limit the amount of virtual memory the process can use, so that my test system does not start swapping. Certain algorithm/test instance combinations hit the memory limit I have defined. Most of the time, the program throws an std::bad_alloc exception, which is printed by the default handler, at which point the program terminates. Occasionally, rather than this happening, the program simply segfaults. Why does my program occasionally segfault when out of memory, rather than reporting an unhandled std::bad_alloc and terminating?

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