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  • Sha or Md5 algorithm i need to encrypt and decrypt in flex

    - by praveen
    Hi I am developing my application in flex and JSP, so when I am passing values through HTTP Service Post method with request object but these values are tracing and modifying by testing team so I am planning to encrypt values in flex and decrypt it in jsp.so is there any algorithms like SHA or MD5 more secure algorithms, so please send any code or related links it is very useful to me. I am using like httpService = new HTTPService; httpService.request = new Object; httpService.request.task = "doInvite"; httpService.request.email = emailInput.text; httpService.request.firstName = firstNameInput.text; httpService.request.lastName = lastNameInput.text; httpService.send(); So is there any other way to give more secure ,please help me in this,Thanks in Advance.

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  • Al Zimmermann's Son of Darts

    - by polygenelubricants
    There's about 2 months left in Al Zimmermann's Son of Darts programming contest, and I'd like to improve my standing (currently in the 60s) to something more respectable. I'd like to get some ideas from the great community of stackoverflow on how best to approach this problem. The contest problem is known as the Global Postage Stamp Problem in literatures. I don't have much experience with optimization algorithms (I know of hillclimbing and simulated annealing in concept only from college), and in fact the program that I have right now is basically sheer brute force, which of course isn't feasible for the larger search spaces. Here are some papers on the subject: A Postage Stamp Problem (Alter & Barnett, 1980) Algorithms for Computing the h-Range of the Postage Stamp Problem (Mossige, 1981) A Postage Stamp Problem (Lunnon, 1986) Two New Techniques for Computing Extremal h-bases Ak (Challis, 1992) Any hints and suggestions are welcome. Also, feel free to direct me to the proper site if stackoverflow isn't it.

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  • What is the relaxation condition in graph theory

    - by windopal
    Hi, I'm trying to understand the main concepts of graph theory and the algorithms within it. Most algorithms seem to contain a "Relaxation Condition" I'm unsure about what this is. Could some one explain it to me please. An example of this is dijkstras algorithm, here is the pseudo-code. 1 function Dijkstra(Graph, source): 2 for each vertex v in Graph: // Initializations 3 dist[v] := infinity // Unknown distance function from source to v 4 previous[v] := undefined // Previous node in optimal path from source 5 dist[source] := 0 // Distance from source to source 6 Q := the set of all nodes in Graph // All nodes in the graph are unoptimized - thus are in Q 7 while Q is not empty: // The main loop 8 u := vertex in Q with smallest dist[] 9 if dist[u] = infinity: 10 break // all remaining vertices are inaccessible from source 11 remove u from Q 12 for each neighbor v of u: // where v has not yet been removed from Q. 13 alt := dist[u] + dist_between(u, v) 14 if alt < dist[v]: // Relax (u,v,a) 15 dist[v] := alt 16 previous[v] := u 17 return dist[] Thanks

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  • what is the best way to generate fake data for classification problem ?

    - by Berkay
    i'm working on a project and i have a subset of user's key-stroke time data.This means that the user makes n attempts and i will use these recorded attempt time data in various kinds of classification algorithms for future user attempts to verify that the login process is done by the user or some another person. (Simply i can say that this is biometrics) I have 3 different times of the user login attempt process, ofcourse this is subset of the infinite data. until now it is an easy classification problem, i decided to use WEKA but as far as i understand i have to create some fake data to feed the classification algorithm. can i use some optimization algorithms ? or is there any way to create this fake data to get min false positives ? Thanks

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  • good books on numerical computation with C

    - by yCalleecharan
    Hi, I've read the post "What is the best book on numerical methods?" and I wish to ask more or less the same question but in relation to C programming. Most of the time, C programming books on numerical methods are just another version of the author's previous Fortran book on the same subject. I've seen Applied numerical methods in C by Nakamura, Shoichiro and the C codes are not good programming practice. I've heard bad comments about Numerical Recipes by Press. Do you know good books on C that discusses numerical methods. It's seem better for me to ask about good books on C discussing numerical methods than rather asking books on numerical methods that discusses C. I've heard about Numerical Algorithms with C by Giesela Engeln-Müllges and A Numerical Library in C for Scientists and Engineers bu Lau but haven't read them. Good books will always have algorithms implemented in the programming language in a smart way. Thanks a lot...

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  • How do i start with Gomoku?

    - by firstTry
    I read about Gomoku that it can be implemented using Minimax and Alpha-Beta Pruning algorithms. So, i read these algorithms and now understand how the game will be solved. But when i sat to down to code, I am facing problem how to approach it. As in , How to design the prototype functions like getNextMove or Max(Move) ? How will the next move searched? Till when should i apply the minimax algorithm. I know i can find the code online, but i want to do it myself. Can anyone please point me in the right direction?

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  • Difference between an LL and Recursive Descent parser?

    - by Noldorin
    I've recently being trying to teach myself how parsers (for languages/context-free grammars) work, and most of it seems to be making sense, except for one thing. I'm focusing my attention in particular on LL(k) grammars, for which the two main algorithms seem to be the LL parser (using stack/parse table) and the Recursive Descent parser (simply using recursion). As far as I can see, the recursive descent algorithm works on all LL(k) grammars and possibly more, whereas an LL parser works on all LL(k) grammars. A recursive descent parser is clearly much simpler than an LL parser to implement, however (just as an LL one is simply than an LR one). So my question is, what are the advantages/problems one might encounter when using either of the algorithms? Why might one ever pick LL over recursive descent, given that it works on the same set of grammars and is trickier to implement? Hopefully this question makes some amount of sense. Sorry if it doesn't - I blame my the fact that this entire subject is almost entirely new to me.

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  • Popularity Algorithm - SQL / Django

    - by RadiantHex
    Hi folks, I've been looking into popularity algorithms used on sites such as Reddit, Digg and even Stackoverflow. Reddit algorithm: t = (time of entry post) - (Dec 8, 2005) x = upvotes - downvotes y = {1 if x > 0, 0 if x = 0, -1 if x < 0) z = {1 if x < 0, otherwise x} log(z) + (y * t)/45000 I have always performed simple ordering within SQL, I'm wondering how I should deal with such ordering. Should it be used to define a table, or could I build an SQL with the ordering within the formula (without hindering performance)? I am also wondering, if it is possible to use multiple ordering algorithms in different occasions, without incurring into performance problems. I'm using Django and PostgreSQL. Help would be much appreciated! ^^

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  • How to optimize MATLAB loops?

    - by striglia
    I have been working lately on a number of iterative algorithms in MATLAB, and been getting hit hard by MATLAB's performance (or lack thereof) when it comes to loops. I'm aware of the benefit of vectorizing code when possible, but are there any tools for optimization when you need the loop for your algorithm? I am aware of the MEX-file option to write small subroutines in C/C++, although given my algorithms, this can be a very painful option given the data structures required. I mainly use MATLAB for the simplicity and speed of prototyping, so a syntactically complex, statically typed language is not ideal for my situation. Are there any other suggestions? Even other languages (python?) which have relatively painless matrix tools are an option.

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  • VS development on FDCC compliant Workstation

    - by paramesh kudlur
    Hi, I have a FDCC compliant workstation with FIPS 140-1 (Level 1) enabled. Now, i cannot run/debug any VS 2005/2008 applications on my machine I get the following error message on my browser Parser Error Message: This implementation is not part of the Windows Platform FIPS validated cryptographic algorithms. the Error points to line no 1 of default.aspx.cs file using system; The only way to successfully debug/run my application is to set the following registry key to 0 HKLM\System\CurrentControlSet\Control\Lsa\fipsalgorithmpolicy I understand that there are some Cryptographic algorithms that are not FIPS compliant on XP SP2 but i am not using cryptography at all. For that matter, the solution contains just default.aspx page with default code in .cs file, and even that fails to run. So my question is why the webpage fails to load, and why the error points to line #1 "using System;" statement? My next question is how can i develop on FIPS compliant locked down maching where i do not have edit rights on registry Thanks kudlur

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  • Most useful parallel programming algorithm?

    - by Zubair
    I recenty asked a question about parallel programming algorithms which was closed quite fast due to my bad ability to communicate my intent: http://stackoverflow.com/questions/2407631/what-is-the-most-useful-parallel-programming-algorithm-closed I had also recently asked another question, specifically: http://stackoverflow.com/questions/2407493/is-mapreduce-such-a-generalisation-of-another-programming-principle/2407570#2407570 The other question was specifically about map reduce and to see if mapreduce was a more specific version of some other concept in parallel programming. This question (about a useful parallel programming algorithm) is more about the whole series of algorithms for parallel programming. You will have to excuse me though as I am quite new to parallel programming, so maybe MapReduce or something that is a more general form of mapreduce is the "only" parallel programming construct which is available, in which case I apologise for my ignorance

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  • shortest path search in a map represented as 2d shapes

    - by joe_shmoe
    Hi, I have a small library of a few shortest path search algorithms. They were developed for simple undirected graphs (the normal representation - vertices and edges). Now I'd like to somehow apply them on a bit different scenario - where the maps are represented as 2-dimensional shapes, connected by shared edges (edges of the polygons, that is). In this scenario, the search can start/end either at a map object or some point (x,y). What would be the best approach? Try to apply the algorithms onto shapes? or try to extract a 'normal' graph out of the shapes (I have preprocessing time available)? Any advice would be much appreciated, as I'm really not sure which way to go, and I don't have enough time (and skill) to explore many options... Thanks a lot

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  • analysis Big Oh notation psuedocode

    - by tesshu
    I'm having trouble getting my head around algorithm analysis. I seem to be okay identifying linear or squared algorithms but am totally lost with nlogn or logn algorithms, these seem to stem mainly from while loops? Heres an example I was looking at: Algorithm Calculate(A,n) Input: Array A of size n t?0 for i?0 to n-1 do if A[i] is an odd number then Q.enqueue(A[i]) else while Q is not empty do t?t+Q.dequeue() while Q is not empty do t?t+Q.dequeue() return t My best guess is the for loop is executed n times, its nested while loop q times making NQ and the final while loop also Q times resulting in O(NQ +Q) which is linear? I am probably totally wrong. Any help would be much appreciated. thanks

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  • Exception - Illegal Block size during decryption(Android)

    - by Vamsi
    I am writing an application which encrypts and decrypts the user notes based on the user set password. i used the following algorithms for encryption/decryption 1. PBEWithSHA256And256BitAES-CBC-BC 2. PBEWithMD5And128BitAES-CBC-OpenSSL e_Cipher = Cipher.getInstance(PBEWithSHA256And256BitAES-CBC-BC); d_Cipher = Cipher.getInstance(PBEWithSHA256And256BitAES-CBC-BC); e_Cipher.init() d_Cipher.init() encryption is working well, but when trying to decrypt it gives Exception - Illegal Block size after encryption i am converting the cipherText to HEX and storing it in a sqlite database. i am retrieving correct values from the sqlite database during decyption but when calling d_Cipher.dofinal() it throws the Exception. I thought i missed to specify the padding and tried to check what are the other available cipher algorithms but i was unable to found. so request you to please give the some knowledge on what are the cipher algorithms and padding that are supported by Android? if the algorithm which i used can be used for padding, how should i specify the padding mechanism? I am pretty new to Encryption so tried a couple of algorithms which are available in BouncyCastle.java but unsuccessful. As requested here is the code public class CryptoHelper { private static final String TAG = "CryptoHelper"; //private static final String PBEWithSHA256And256BitAES = "PBEWithSHA256And256BitAES-CBC-BC"; //private static final String PBEWithSHA256And256BitAES = "PBEWithMD5And128BitAES-CBC-OpenSSL"; private static final String PBEWithSHA256And256BitAES = "PBEWithMD5And128BitAES-CBC-OpenSSLPBEWITHSHA1AND3-KEYTRIPLEDES-CB"; private static final String randomAlgorithm = "SHA1PRNG"; public static final int SALT_LENGTH = 8; public static final int SALT_GEN_ITER_COUNT = 20; private final static String HEX = "0123456789ABCDEF"; private Cipher e_Cipher; private Cipher d_Cipher; private SecretKey secretKey; private byte salt[]; public CryptoHelper(String password) throws InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidAlgorithmParameterException, InvalidKeySpecException { char[] cPassword = password.toCharArray(); PBEKeySpec pbeKeySpec = new PBEKeySpec(cPassword); PBEParameterSpec pbeParamSpec = new PBEParameterSpec(salt, SALT_GEN_ITER_COUNT); SecretKeyFactory keyFac = SecretKeyFactory.getInstance(PBEWithSHA256And256BitAES); secretKey = keyFac.generateSecret(pbeKeySpec); SecureRandom saltGen = SecureRandom.getInstance(randomAlgorithm); this.salt = new byte[SALT_LENGTH]; saltGen.nextBytes(this.salt); e_Cipher = Cipher.getInstance(PBEWithSHA256And256BitAES); d_Cipher = Cipher.getInstance(PBEWithSHA256And256BitAES); e_Cipher.init(Cipher.ENCRYPT_MODE, secretKey, pbeParamSpec); d_Cipher.init(Cipher.DECRYPT_MODE, secretKey, pbeParamSpec); } public String encrypt(String cleartext) throws IllegalBlockSizeException, BadPaddingException { byte[] encrypted = e_Cipher.doFinal(cleartext.getBytes()); return convertByteArrayToHex(encrypted); } public String decrypt(String cipherString) throws IllegalBlockSizeException { byte[] plainText = decrypt(convertStringtobyte(cipherString)); return(new String(plainText)); } public byte[] decrypt(byte[] ciphertext) throws IllegalBlockSizeException { byte[] retVal = {(byte)0x00}; try { retVal = d_Cipher.doFinal(ciphertext); } catch (BadPaddingException e) { Log.e(TAG, e.toString()); } return retVal; } public String convertByteArrayToHex(byte[] buf) { if (buf == null) return ""; StringBuffer result = new StringBuffer(2*buf.length); for (int i = 0; i < buf.length; i++) { appendHex(result, buf[i]); } return result.toString(); } private static void appendHex(StringBuffer sb, byte b) { sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f)); } private static byte[] convertStringtobyte(String hexString) { int len = hexString.length()/2; byte[] result = new byte[len]; for (int i = 0; i < len; i++) { result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue(); } return result; } public byte[] getSalt() { return salt; } public SecretKey getSecretKey() { return secretKey; } public static SecretKey createSecretKey(char[] password) throws NoSuchAlgorithmException, InvalidKeySpecException { PBEKeySpec pbeKeySpec = new PBEKeySpec(password); SecretKeyFactory keyFac = SecretKeyFactory.getInstance(PBEWithSHA256And256BitAES); return keyFac.generateSecret(pbeKeySpec); } } I will call mCryptoHelper.decrypt(String str) then this results in Illegal block size exception My Env: Android 1.6 on Eclipse

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  • circuit/block-diagram drawing

    - by JCLL
    I'm looking for either algorithms or visualization tool for (nice) circuit/block-diagram drawing. I am also interested in a general formulation of the problem. By "circuit drawing", I mean the capability of exploring place & route for block-diagrams (rectangles) with I/O ports and their connections (wires). These block-diagrams can be hierarchical i.e some blocks may have some nested internal sub-structure etc. This topic is strongly related to classical graph-drawing, with the supplemental constraint of the need to take ports location into account, and possibly the shape of the blocks (rectangle of various sizes). Graphviz tools do not respond to the problem (at least my previous experiments have not been satisfactory). Force-directed algorithms retain my attention, but I have just found papers on classical directed graphs. Any hints ?

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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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  • Where can I learn more about datastructure tricky questions?

    - by Sandbox
    I am relatively new to programming (around 1 year programming C#-winforms). Also, I come from a non CS background (no formal degree) Recently, while being interviewed for a job, I was asked about implementing a queue using a stack. I fumbled and wan't able to answer the question. After, the interview I could do it(had to spend some time). I have learnt (and think that I know it well) basic algorithms in datastructures using the book Data Structures: A Pseudocode Approach with C - Richard F. Gilberg (Author) . I want to know about sites/ books which have such questions along with answers. I think this will allow me to develop my CS specific problem solving skills. Any help is appreciated. BOUNTY: I am looking at some blog/website with datastructure and algorithms Q&A.

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  • Algorithm to distribute objects in a box (like InDesign, Illustrator, Draw!)

    - by Rafael Almeida
    I have a set of rectangles with their corresponding positions and a big rectangle which serves as the 'bounding box' for these rectangles. I would like to know of an algorithm that would 'distribute the free space' evenly among the rectangles. Some of you may be familiar with the Distribute Spacing option in Adobe InDesign and similar layout-oriented apps. That would be what I'm looking for. I did try looking it up, but I'm not familiar with 'graphical' algorithms terminology and trying only terms relating to 'distribute' mainly yields results about Distributed Computing. So, even the names of the algorithms or better terms to look up would be a big help. Finally, the algorithm doesn't need to be rigorously the same as InDesign's one: pretty much any algorithm that 'distributes' objects inside a region will work fine. In fact, since I'm striving for visual appeal mainly, the more suggestions the better. =D

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  • Which set(s) of video lectures for computer science?

    - by SebKom
    As most of you know a couple of top universities (MIT, Stanford, etc) around the world are now publishing videos of their lectures online. I am advancing to the third and final year of my computer science degree this September and I was thinking about spending some time during the summer to watch a couple of lectures, in order to improve my understanding of algorithms, complexity, programming, software engineering, etc. Now I don't have infinite time to spend so I can't watch all of the lectures from all of the universities so I was wondering if you could suggest me which sets to watch from each one (something like "Algorithms from MIT", "Programming from Yale", etc).

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  • Versioning issues with assemblies

    - by devoured elysium
    Let's assume I have two assemblies: MyExecutable.dll version 1.0.0 MyClassLibrary.dll version 1.0.0 Now, MyExecutable.dll currently uses MyClassLibrary.dll's classes and methods (which include some algorithms). Most of those algorithms were made on the run, being that later I'll want to refine them if needed. This means, I won't change the interface of those classes but the code itself will see some changes. The question at hand is, MyExecutable.dll will be expecting MyClassLibrary.dll 1.0.0 and I'll want it to use version 1.0.1 (or something like that). I don't want to have to recompile MyExecutable.dll(because actually there might be more than just one executable using MyClassLibrary.dll). Is there a solution for this problem? I've heard about the GAC, but if possible I'd like to stay away from it. Thanks

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  • some examples for using specific searchalgorithm

    - by Robert
    I could understand the following search algorithms: Constraint Satisfaction with Arc Consistency, Uninformed search A* Search MinMax I would understand the definition and working principles of the above algorithm,but could you please give me some real world examples that the above algorithms will be suitable?My idea would be: For CSP with Arc Consistency,assign students to groups that each group must contain both technical and management students,and no 2 technical students in a same group. Uniformed Search: search for a file under UNIX directoy. A* Search: search a way (staring from home) to go to mulitple stores to buy things then get back home with minimum total travelling time. MinMax:Go or other Chess. Please correct me if I am wrong.

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  • Whats the deal with python?

    - by gmatt
    My interests in programming lie mainly in algorithms, and lately I have seen many reputable researchers write a lot of their code in python. How easy and convenient is python for scientific computing? Does it have a library of algorithms that compares to matlab's? Is Python a scripting language or does it compile? Is it a great language for prototyping an algorithm? How long would it take me to learn enough of it to be productive provided I know C well and OO programming somewhat? Is it OO based? Sorry for the condensed format of questions, but I'm very curious and was hoping a more experienced programmer could help me out.

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  • CAD/CAM without C++

    - by zaladane
    Hello, Is it possible to do CAD/CAM software without having to use C++? My company developed their software with c/C++ but that was more than 10 years ago. Today,there is a lot of legacy code that switching would force us to get rid of but i was wondering what the actual risks are. We have a lot of mathematical algorithms for toolpath calculations, feature recognition and simulation and 3D Rendering and i was wondering if C# can handles all of that without great performance loss. Is it a utopia to rewrite such algorithms in c# or should that language only deal with UI. We are not talking about game development here (Halo 3 or Call Of Duty) so how much processing does CAD/CAM really need? Can anybody enlighten me on this matter? Most of my colleagues are hardcore C++ programmers and although i program in c++ i love .NET but i am having a hard time selling .NET to them other than basic UI. Does it make sense to consider switching to .NET in such a field, or is it just not a wise idea? Thank you

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