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• Apriori Algorithm- what to do with small min.support?

  - by user3707650

  I have a question about the table beneath my question: If i was told that the given min.support=10%, how can i know what is the support count, by which i will use during the exercise? What i know is: that you take the number of transactions (8) and multiple it by the min.support: 8*(10/100)=0.8 the problem is that i get this number: 0.8, how can i use this support count during this example?? 0.8 is a number that will make me prune all combination set that i will build... please help me!!! TID A B C D E F G 10 1 0 1 0 0 0 1 20 1 1 1 1 0 1 1 30 0 0 0 0 0 0 1 40 0 0 1 0 0 1 1 50 0 0 0 1 1 0 0 60 0 1 1 0 1 1 0 70 0 0 0 0 1 1 0 80 0 0 1 0 1 1 1

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• is it possible to apply an RC5 algorithm on an audio file in c++ ?

  - by mekasperasky

  is it possible to encrypt an audio file in c++ using rc5?

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• What kind of memory reclamation algorithm does MRI Ruby 1.8 use?

  - by Foo

  In other languages you have a number of possibilities usually for memory reclamation: Mark objects and then remove them Explicit retain and release Count references to objects Internal heap disposition How does Ruby work?

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• Breadcrumb for multiple categories

  - by Damodar Bashyal

  I post in multiple categories, so is it better to have: Consulting Services Implementation Service A Consulting Services Optimization Service A Consulting Services Upgrade Service A or, Consulting Services Implementation, Optimization, Upgrade Service A I was doing second way, the problem is google doesn't show 3rd set of crumbs. ie it only displays: Consulting Services on search result. But having multiple breadcrumbs on the page doesn't look good. any suugestions? Update For @PatomaS 's question I mean 3 lines of breadcrumbs, see above i have posted same article (Service A) in 3 categories (Implementation, Optimization, Upgrade). So you can reach same article through 3 categories. So whats the best breadcrumb to display on article 'Service A'?

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• How do I know if I've gone too far with processing things in a game?

  - by ThePlan

  A common programming quote I see every day is: Premature optimization is the root of all evil! I admit I'm one of those guys that like to do premature optimization in a pretty obssessive manner but that's probably because I'm not aware how powerful modern processors are. I can think of lots of sollutions for a problem, but all of them are tough on the memory side, and I keep thinking "This will hurt me more in the future when I'll have to re-do it because it's bad performance-wise." How do you know when the code you are thinking of is going too far and is not a case of premature optimization? How much can your game handle at a time before performance becomes a problem?

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• ANN for decompiler?

  - by Rhythmic Algorithm

  Has there ever been any attempts at utilizing artificial neural networks in decompilation? It would be nice if it was possible to provide the trimmed semantics of source along with the code in to a neural network so it could learn the connection between the two. I assume this would likely lose it's effectiveness when there is optimizations and maybe work better for high level languages too but I'm interested in hearing any attempts anyone has had at this.

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• Google street view URL question:

  - by Rhythmic Algorithm

  Hi I have the address of a property and my application can launch a browser to go to http://maps.google.com?q=searchStringHere. If a good match is found it will take it directly there. Is there any thing I can append to the url to make it switch to streetview without having the exact coordinates? I dont't want to code any javascript or flash.

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• Change save to file name but from the client

  - by Rhythmic Algorithm

  This question asks about file name the servers sends and the fix was quite simply a content-disposition header in the http response. What I interested in is does anyone know of any way to do this from the client side if the file name is already known? Is there any special javascript to do this for example? A site I have to use but not mine has a FileDownload.aspx but it doesn't send the content-disposition header. I know the filename and would like to be able to create a firefox extensions to use for the poorly coded web site. Thanks

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• C++ .NET DLL vs C# Managed Code ? (File Encrypting AES-128+XTS)

  - by Ranhiru

  I need to create a Windows Mobile Application (WinMo 6.x - C#) which is used to encrypt/decrypt files. However it is my duty to write the encryption algorithm which is AES-128 along with XTS as the mode of operation. RijndaelManaged just doesn't cut it :( Very much slower than DES and 3DES CryptoServiceProviders :O I know it all depends on how good I am at writing the algorithm in the most efficient way. (And yes I my self have to write it from scratch but i can take a look @ other implementations) Nevertheless, does writing a C++ .NET DLL to create the encryption/decryption algorithm + all the file handling and using it from C# have a significant performance advantage OVER writing the encryption algorithm + file handling in completely managed C# code? If I use C++ .NET to create the encryption algorithm, should I use MFC Smart Device DLL or ATL? What is the difference and is there any impact on which one I choose? And can i just add a reference to the C++ DLL from C# or should I use P/Invoke? I am fairly competent with C# than C++ but performance plays a major role as I have convinced my lecturers that AES is a very efficient cryptographic algorithm for resource constrained devices. Thanx a bunch :)

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• 10 Essential Tools for building ASP.NET Websites

  - by Stephen Walther

  I recently put together a simple public website created with ASP.NET for my company at Superexpert.com. I was surprised by the number of free tools that I ended up using to put together the website. Therefore, I thought it would be interesting to create a list of essential tools for building ASP.NET websites. These tools work equally well with both ASP.NET Web Forms and ASP.NET MVC. Performance Tools After reading Steve Souders two (very excellent) books on front-end website performance High Performance Web Sites and Even Faster Web Sites, I have been super sensitive to front-end website performance. According to Souders’ Performance Golden Rule: “Optimize front-end performance first, that's where 80% or more of the end-user response time is spent” You can use the tools below to reduce the size of the images, JavaScript files, and CSS files used by an ASP.NET application. 1. Sprite and Image Optimization Framework CSS sprites were first described in an article written for A List Apart entitled CSS sprites: Image Slicing’s Kiss of Death. When you use sprites, you combine multiple images used by a website into a single image. Next, you use CSS trickery to display particular sub-images from the combined image in a webpage. The primary advantage of sprites is that they reduce the number of requests required to display a webpage. Requesting a single large image is faster than requesting multiple small images. In general, the more resources – images, JavaScript files, CSS files – that must be moved across the wire, the slower your website. However, most people avoid using sprites because they require a lot of work. You need to combine all of the images and write just the right CSS rules to display the sub-images. The Microsoft Sprite and Image Optimization Framework enables you to avoid all of this work. The framework combines the images for you automatically. Furthermore, the framework includes an ASP.NET Web Forms control and an ASP.NET MVC helper that makes it easy to display the sub-images. You can download the Sprite and Image Optimization Framework from CodePlex at http://aspnet.codeplex.com/releases/view/50869. The Sprite and Image Optimization Framework was written by Morgan McClean who worked in the office next to mine at Microsoft. Morgan was a scary smart Intern from Canada and we discussed the Framework while he was building it (I was really excited to learn that he was working on it). Morgan added some great advanced features to this framework. For example, the Sprite and Image Optimization Framework supports something called image inlining. When you use image inlining, the actual image is stored in the CSS file. Here’s an example of what image inlining looks like: .Home_StephenWalther_small-jpg { width:75px; height:100px; background: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAEsAAABkCAIAAABB1lpeAAAAB GdBTUEAALGOfPtRkwAAACBjSFJNAACHDwAAjA8AAP1SAACBQAAAfXkAAOmLAAA85QAAGcxzPIV3AAAKL s+zNfREAAAAASUVORK5CYII=) no-repeat 0% 0%; } The actual image (in this case a picture of me that is displayed on the home page of the Superexpert.com website) is stored in the CSS file. If you visit the Superexpert.com website then very few separate images are downloaded. For example, all of the images with a red border in the screenshot below take advantage of CSS sprites: Unfortunately, there are some significant Gotchas that you need to be aware of when using the Sprite and Image Optimization Framework. There are workarounds for these Gotchas. I plan to write about these Gotchas and workarounds in a future blog entry. 2. Microsoft Ajax Minifier Whenever possible you should combine, minify, compress, and cache with a far future header all of your JavaScript and CSS files. The Microsoft Ajax Minifier makes it easy to minify JavaScript and CSS files. Don’t confuse minification and compression. You need to do both. According to Souders, you can reduce the size of a JavaScript file by an additional 20% (on average) by minifying a JavaScript file after you compress the file. When you minify a JavaScript or CSS file, you use various tricks to reduce the size of the file before you compress the file. For example, you can minify a JavaScript file by replacing long JavaScript variables names with short variables names and removing unnecessary white space and comments. You can minify a CSS file by doing such things as replacing long color names such as #ffffff with shorter equivalents such as #fff. The Microsoft Ajax Minifier was created by Microsoft employee Ron Logan. Internally, this tool was being used by several large Microsoft websites. We also used the tool heavily on the ASP.NET team. I convinced Ron to publish the tool on CodePlex so that everyone in the world could take advantage of it. You can download the tool from the ASP.NET Ajax website and read documentation for the tool here. I created the installer for the Microsoft Ajax Minifier. When creating the installer, I also created a Visual Studio build task to make it easy to minify all of your JavaScript and CSS files whenever you do a build within Visual Studio automatically. Read the Ajax Minifier Quick Start to learn how to configure the build task. 3. ySlow The ySlow tool is a free add-on for Firefox created by Yahoo that enables you to test the front-end of your website. For example, here are the current test results for the Superexpert.com website: The Superexpert.com website has an overall score of B (not perfect but not bad). The ySlow tool is not perfect. For example, the Superexpert.com website received a failing grade of F for not using a Content Delivery Network even though the website using the Microsoft Ajax Content Delivery Network for JavaScript files such as jQuery. Uptime After publishing a website live to the world, you want to ensure that the website does not encounter any issues and that it stays live. I use the following tools to monitor the Superexpert.com website now that it is live. 4. ELMAH ELMAH stands for Error Logging Modules and Handlers for ASP.NET. ELMAH enables you to record any errors that happen at your website so you can review them in the future. You can download ELMAH for free from the ELMAH project website. ELMAH works great with both ASP.NET Web Forms and ASP.NET MVC. You can configure ELMAH to store errors in a number of different stores including XML files, the Event Log, an Access database, a SQL database, an Oracle database, or in computer RAM. You also can configure ELMAH to email error messages to you when they happen. By default, you can access ELMAH by requesting the elmah.axd page from a website with ELMAH installed. Here’s what the elmah page looks like from the Superexpert.com website (this page is password-protected because secret information can be revealed in an error message): If you click on a particular error message, you can view the original Yellow Screen ASP.NET error message (even when the error message was never displayed to the actual user). I installed ELMAH by taking advantage of the new package manager for ASP.NET named NuGet (originally named NuPack). You can read the details about NuGet in the following blog entry by Scott Guthrie. You can download NuGet from CodePlex. 5. Pingdom I use Pingdom to verify that the Superexpert.com website is always up. You can sign up for Pingdom by visiting Pingdom.com. You can use Pingdom to monitor a single website for free. At the Pingdom website, you configure the frequency that your website gets pinged. I verify that the Superexpert.com website is up every 5 minutes. I have the Pingdom service verify that it can retrieve the string “Contact Us” from the website homepage. If your website goes down, you can configure Pingdom so that it sends an email, Twitter, SMS, or iPhone alert. I use the Pingdom iPhone app which looks like this: 6. Host Tracker If your website does go down then you need some way of determining whether it is a problem with your local network or if your website is down for everyone. I use a website named Host-Tracker.com to check how badly a website is down. Here’s what the Host-Tracker website displays for the Superexpert.com website when the website can be successfully pinged from everywhere in the world: Notice that Host-Tracker pinged the Superexpert.com website from 68 locations including Roubaix, France and Scranton, PA. Debugging I mean debugging in the broadest possible sense. I use the following tools when building a website to verify that I have not made a mistake. 7. HTML Spell Checker Why doesn’t Visual Studio have a built-in spell checker? Don’t know – I’ve always found this mysterious. Fortunately, however, a former member of the ASP.NET team wrote a free spell checker that you can use with your ASP.NET pages. I find a spell checker indispensible. It is easy to delude yourself that you are capable of perfect spelling. I’m always super embarrassed when I actually run the spell checking tool and discover all of my spelling mistakes. The fastest way to add the HTML Spell Checker extension to Visual Studio is to select the menu option Tools, Extension Manager within Visual Studio. Click on Online Gallery and search for HTML Spell Checker: 8. IIS SEO Toolkit If people cannot find your website through Google then you should not even bother to create it. Microsoft has a great extension for IIS named the IIS Search Engine Optimization Toolkit that you can use to identify issue with your website that would hurt its page rank. You also can use this tool to quickly create a sitemap for your website that you can submit to Google or Bing. You can even generate the sitemap for an ASP.NET MVC website. Here’s what the report overview for the Superexpert.com website looks like: Notice that the Sueprexpert.com website had plenty of violations. For example, there are 65 cases in which a page has a broken hyperlink. You can drill into these violations to identity the exact page and location where these violations occur. 9. LinqPad If your ASP.NET website accesses a database then you should be using LINQ to Entities with the Entity Framework. Using LINQ involves some magic. LINQ queries written in C# get converted into SQL queries for you. If you are not careful about how you write your LINQ queries, you could unintentionally build a really badly performing website. LinqPad is a free tool that enables you to experiment with your LINQ queries. It even works with Microsoft SQL CE 4 and Azure. You can use LinqPad to execute a LINQ to Entities query and see the results. You also can use it to see the resulting SQL that gets executed against the database: 10. .NET Reflector I use .NET Reflector daily. The .NET Reflector tool enables you to take any assembly and disassemble the assembly into C# or VB.NET code. You can use .NET Reflector to see the “Source Code” of an assembly even when you do not have the actual source code. You can download a free version of .NET Reflector from the Redgate website. I use .NET Reflector primarily to help me understand what code is doing internally. For example, I used .NET Reflector with the Sprite and Image Optimization Framework to better understand how the MVC Image helper works. Here’s part of the disassembled code from the Image helper class: Summary In this blog entry, I’ve discussed several of the tools that I used to create the Superexpert.com website. These are tools that I use to improve the performance, improve the SEO, verify the uptime, or debug the Superexpert.com website. All of the tools discussed in this blog entry are free. Furthermore, all of these tools work with both ASP.NET Web Forms and ASP.NET MVC. Let me know if there are any tools that you use daily when building ASP.NET websites.

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• while(true) and loop-breaking - anti-pattern?

  - by KeithS

  Consider the following code: public void doSomething(int input) { while(true) { TransformInSomeWay(input); if(ProcessingComplete(input)) break; DoSomethingElseTo(input); } } Assume that this process involves a finite but input-dependent number of steps; the loop is designed to terminate on its own as a result of the algorithm, and is not designed to run indefinitely (until cancelled by an outside event). Because the test to see if the loop should end is in the middle of a logical set of steps, the while loop itself currently doesn't check anything meaningful; the check is instead performed at the "proper" place within the conceptual algorithm. I was told that this is bad code, because it is more bug-prone due to the ending condition not being checked by the loop structure. It's more difficult to figure out how you'd exit the loop, and could invite bugs as the breaking condition might be bypassed or omitted accidentally given future changes. Now, the code could be structured as follows: public void doSomething(int input) { TransformInSomeWay(input); while(!ProcessingComplete(input)) { DoSomethingElseTo(input); TransformInSomeWay(input); } } However, this duplicates a call to a method in code, violating DRY; if TransformInSomeWay were later replaced with some other method, both calls would have to be found and changed (and the fact that there are two may be less obvious in a more complex piece of code). You could also write it like: public void doSomething(int input) { var complete = false; while(!complete) { TransformInSomeWay(input); complete = ProcessingComplete(input); if(!complete) { DoSomethingElseTo(input); } } } ... but you now have a variable whose only purpose is to shift the condition-checking to the loop structure, and also has to be checked multiple times to provide the same behavior as the original logic. For my part, I say that given the algorithm this code implements in the real world, the original code is the most readable. If you were going through it yourself, this is the way you'd think about it, and so it would be intuitive to people familiar with the algorithm. So, which is "better"? is it better to give the responsibility of condition checking to the while loop by structuring the logic around the loop? Or is it better to structure the logic in a "natural" way as indicated by requirements or a conceptual description of the algorithm, even though that may mean bypassing the loop's built-in capabilities?

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• Elfsign Object Signing on Solaris

  - by danx

  Elfsign Object Signing on Solaris Don't let this happen to you—use elfsign! Solaris elfsign(1) is a command that signs and verifies ELF format executables. That includes not just executable programs (such as ls or cp), but other ELF format files including libraries (such as libnvpair.so) and kernel modules (such as autofs). Elfsign has been available since Solaris 10 and ELF format files distributed with Solaris, since Solaris 10, are signed by either Sun Microsystems or its successor, Oracle Corporation. When an ELF file is signed, elfsign adds a new section the ELF file, .SUNW_signature, that contains a RSA public key signature and other information about the signer. That is, the algorithm used, algorithm OID, signer CN/OU, and time stamp. The signature section can later be verified by elfsign or other software by matching the signature in the file agains the ELF file contents (excluding the signature). ELF executable files may also be signed by a 3rd-party or by the customer. This is useful for verifying the origin and authenticity of executable files installed on a system. The 3rd-party or customer public key certificate should be installed in /etc/certs/ to allow verification by elfsign. For currently-released versions of Solaris, only cryptographic framework plugin libraries are verified by Solaris. However, all ELF files may be verified by the elfsign command at any time. Elfsign Algorithms Elfsign signatures are created by taking a digest of the ELF section contents, then signing the digest with RSA. To verify, one takes a digest of ELF file and compares with the expected digest that's computed from the signature and RSA public key. Originally elfsign took a MD5 digest of a SHA-1 digest of the ELF file sections, then signed the resulting digest with RSA. In Solaris 11.1 then Solaris 11.1 SRU 7 (5/2013), the elfsign crypto algorithms available have been expanded to keep up with evolving cryptography. The following table shows the available elfsign algorithms: Elfsign Algorithm Solaris Release Comments elfsign sign -F rsa_md5_sha1   S10, S11.0, S11.1 Default for S10. Not recommended* elfsign sign -F rsa_sha1 S11.1 Default for S11.1. Not recommended elfsign sign -F rsa_sha256 S11.1 patch SRU7+   Recommended ___ *Most or all CAs do not accept MD5 CSRs and do not issue MD5 certs due to MD5 hash collision problems. RSA Key Length. I recommend using RSA-2048 key length with elfsign is RSA-2048 as the best balance between a long expected "life time", interoperability, and performance. RSA-2048 keys have an expected lifetime through 2030 (and probably beyond). For details, see Recommendation for Key Management: Part 1: General, NIST Publication SP 800-57 part 1 (rev. 3, 7/2012, PDF), tables 2 and 4 (pp. 64, 67). Step 1: create or obtain a key and cert The first step in using elfsign is to obtain a key and cert from a public Certificate Authority (CA), or create your own self-signed key and cert. I'll briefly explain both methods. Obtaining a Certificate from a CA To obtain a cert from a CA, such as Verisign, Thawte, or Go Daddy (to name a few random examples), you create a private key and a Certificate Signing Request (CSR) file and send it to the CA, following the instructions of the CA on their website. They send back a signed public key certificate. The public key cert, along with the private key you created is used by elfsign to sign an ELF file. The public key cert is distributed with the software and is used by elfsign to verify elfsign signatures in ELF files. You need to request a RSA "Class 3 public key certificate", which is used for servers and software signing. Elfsign uses RSA and we recommend RSA-2048 keys. The private key and CSR can be generated with openssl(1) or pktool(1) on Solaris. Here's a simple example that uses pktool to generate a private RSA_2048 key and a CSR for sending to a CA: $ pktool gencsr keystore=file format=pem outcsr=MYCSR.p10 \ subject="CN=canineswworks.com,OU=Canine SW object signing" \ outkey=MYPRIVATEKEY.key $ openssl rsa -noout -text -in MYPRIVATEKEY.key Private-Key: (2048 bit) modulus: 00:d2:ef:42:f2:0b:8c:96:9f:45:32:fc:fe:54:94: . . . [omitted for brevity] . . . c9:c7 publicExponent: 65537 (0x10001) privateExponent: 26:14:fc:49:26:bc:a3:14:ee:31:5e:6b:ac:69:83: . . . [omitted for brevity] . . . 81 prime1: 00:f6:b7:52:73:bc:26:57:26:c8:11:eb:6c:dc:cb: . . . [omitted for brevity] . . . bc:91:d0:40:d6:9d:ac:b5:69 prime2: 00:da:df:3f:56:b2:18:46:e1:89:5b:6c:f1:1a:41: . . . [omitted for brevity] . . . f3:b7:48:de:c3:d9:ce:af:af exponent1: 00:b9:a2:00:11:02:ed:9a:3f:9c:e4:16:ce:c7:67: . . . [omitted for brevity] . . . 55:50:25:70:d3:ca:b9:ab:99 exponent2: 00:c8:fc:f5:57:11:98:85:8e:9a:ea:1f:f2:8f:df: . . . [omitted for brevity] . . . 23:57:0e:4d:b2:a0:12:d2:f5 coefficient: 2f:60:21:cd:dc:52:76:67:1a:d8:75:3e:7f:b0:64: . . . [omitted for brevity] . . . 06:94:56:d8:9d:5c:8e:9b $ openssl req -noout -text -in MYCSR.p10 Certificate Request: Data: Version: 2 (0x2) Subject: OU=Canine SW object signing, CN=canineswworks.com Subject Public Key Info: Public Key Algorithm: rsaEncryption Public-Key: (2048 bit) Modulus: 00:d2:ef:42:f2:0b:8c:96:9f:45:32:fc:fe:54:94: . . . [omitted for brevity] . . . c9:c7 Exponent: 65537 (0x10001) Attributes: Signature Algorithm: sha1WithRSAEncryption b3:e8:30:5b:88:37:68:1c:26:6b:45:af:5e:de:ea:60:87:ea: . . . [omitted for brevity] . . . 06:f9:ed:b4 Secure storage of RSA private key. The private key needs to be protected if the key signing is used for production (as opposed to just testing). That is, protect the key to protect against unauthorized signatures by others. One method is to use a PIN-protected PKCS#11 keystore. The private key you generate should be stored in a secure manner, such as in a PKCS#11 keystore using pktool(1). Otherwise others can sign your signature. Other secure key storage mechanisms include a SCA-6000 crypto card, a USB thumb drive stored in a locked area, a dedicated server with restricted access, Oracle Key Manager (OKM), or some combination of these. I also recommend secure backup of the private key. Here's an example of generating a private key protected in the PKCS#11 keystore, and a CSR. $ pktool setpin # use if PIN not set yet Enter token passphrase: changeme Create new passphrase: Re-enter new passphrase: Passphrase changed. $ pktool gencsr keystore=pkcs11 label=MYPRIVATEKEY \ format=pem outcsr=MYCSR.p10 \ subject="CN=canineswworks.com,OU=Canine SW object signing" $ pktool list keystore=pkcs11 Enter PIN for Sun Software PKCS#11 softtoken: Found 1 asymmetric public keys. Key #1 - RSA public key: MYPRIVATEKEY Here's another example that uses openssl instead of pktool to generate a private key and CSR: $ openssl genrsa -out cert.key 2048 $ openssl req -new -key cert.key -out MYCSR.p10 Self-Signed Cert You can use openssl or pktool to create a private key and a self-signed public key certificate. A self-signed cert is useful for development, testing, and internal use. The private key created should be stored in a secure manner, as mentioned above. The following example creates a private key, MYSELFSIGNED.key, and a public key cert, MYSELFSIGNED.pem, using pktool and displays the contents with the openssl command. $ pktool gencert keystore=file format=pem serial=0xD06F00D lifetime=20-year \ keytype=rsa hash=sha256 outcert=MYSELFSIGNED.pem outkey=MYSELFSIGNED.key \ subject="O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com" $ pktool list keystore=file objtype=cert infile=MYSELFSIGNED.pem Found 1 certificates. 1. (X.509 certificate) Filename: MYSELFSIGNED.pem ID: c8:24:59:08:2b:ae:6e:5c:bc:26:bd:ef:0a:9c:54:de:dd:0f:60:46 Subject: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com Issuer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com Not Before: Oct 17 23:18:00 2013 GMT Not After: Oct 12 23:18:00 2033 GMT Serial: 0xD06F00D0 Signature Algorithm: sha256WithRSAEncryption $ openssl x509 -noout -text -in MYSELFSIGNED.pem Certificate: Data: Version: 3 (0x2) Serial Number: 3496935632 (0xd06f00d0) Signature Algorithm: sha256WithRSAEncryption Issuer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com Validity Not Before: Oct 17 23:18:00 2013 GMT Not After : Oct 12 23:18:00 2033 GMT Subject: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com Subject Public Key Info: Public Key Algorithm: rsaEncryption Public-Key: (2048 bit) Modulus: 00:bb:e8:11:21:d9:4b:88:53:8b:6c:5a:7a:38:8b: . . . [omitted for brevity] . . . bf:77 Exponent: 65537 (0x10001) Signature Algorithm: sha256WithRSAEncryption 9e:39:fe:c8:44:5c:87:2c:8f:f4:24:f6:0c:9a:2f:64:84:d1: . . . [omitted for brevity] . . . 5f:78:8e:e8 $ openssl rsa -noout -text -in MYSELFSIGNED.key Private-Key: (2048 bit) modulus: 00:bb:e8:11:21:d9:4b:88:53:8b:6c:5a:7a:38:8b: . . . [omitted for brevity] . . . bf:77 publicExponent: 65537 (0x10001) privateExponent: 0a:06:0f:23:e7:1b:88:62:2c:85:d3:2d:c1:e6:6e: . . . [omitted for brevity] . . . 9c:e1:e0:0a:52:77:29:4a:75:aa:02:d8:af:53:24: c1 prime1: 00:ea:12:02:bb:5a:0f:5a:d8:a9:95:b2:ba:30:15: . . . [omitted for brevity] . . . 5b:ca:9c:7c:19:48:77:1e:5d prime2: 00:cd:82:da:84:71:1d:18:52:cb:c6:4d:74:14:be: . . . [omitted for brevity] . . . 5f:db:d5:5e:47:89:a7:ef:e3 exponent1: 32:37:62:f6:a6:bf:9c:91:d6:f0:12:c3:f7:04:e9: . . . [omitted for brevity] . . . 97:3e:33:31:89:66:64:d1 exponent2: 00:88:a2:e8:90:47:f8:75:34:8f:41:50:3b:ce:93: . . . [omitted for brevity] . . . ff:74:d4:be:f3:47:45:bd:cb coefficient: 4d:7c:09:4c:34:73:c4:26:f0:58:f5:e1:45:3c:af: . . . [omitted for brevity] . . . af:01:5f:af:ad:6a:09:bf Step 2: Sign the ELF File object By now you should have your private key, and obtained, by hook or crook, a cert (either from a CA or use one you created (a self-signed cert). The next step is to sign one or more objects with your private key and cert. Here's a simple example that creates an object file, signs, verifies, and lists the contents of the ELF signature. $ echo '#include <stdio.h>\nint main(){printf("Hello\\n");}'>hello.c $ make hello cc -o hello hello.c $ elfsign verify -v -c MYSELFSIGNED.pem -e hello elfsign: no signature found in hello. $ elfsign sign -F rsa_sha256 -v -k MYSELFSIGNED.key -c MYSELFSIGNED.pem -e hello elfsign: hello signed successfully. format: rsa_sha256. signer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com. signed on: October 17, 2013 04:22:49 PM PDT. $ elfsign list -f format -e hello rsa_sha256 $ elfsign list -f signer -e hello O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com $ elfsign list -f time -e hello October 17, 2013 04:22:49 PM PDT $ elfsign verify -v -c MYSELFSIGNED.key -e hello elfsign: verification of hello failed. format: rsa_sha256. signer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com. signed on: October 17, 2013 04:22:49 PM PDT. Signing using the pkcs11 keystore To sign the ELF file using a private key in the secure pkcs11 keystore, replace "-K MYSELFSIGNED.key" in the "elfsign sign" command line with "-T MYPRIVATEKEY", where MYPRIVATKEY is the pkcs11 token label. Step 3: Install the cert and test on another system Just signing the object isn't enough. You need to copy or install the cert and the signed ELF file(s) on another system to test that the signature is OK. Your public key cert should be installed in /etc/certs. Use elfsign verify to verify the signature. Elfsign verify checks each cert in /etc/certs until it finds one that matches the elfsign signature in the file. If one isn't found, the verification fails. Here's an example: $ su Password: # rm /etc/certs/MYSELFSIGNED.key # cp MYSELFSIGNED.pem /etc/certs # exit $ elfsign verify -v hello elfsign: verification of hello passed. format: rsa_sha256. signer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com. signed on: October 17, 2013 04:24:20 PM PDT. After testing, package your cert along with your ELF object to allow elfsign verification after your cert and object are installed or copied. Under the Hood: elfsign verification Here's the steps taken to verify a ELF file signed with elfsign. The steps to sign the file are similar except the private key exponent is used instead of the public key exponent and the .SUNW_signature section is written to the ELF file instead of being read from the file. Generate a digest (SHA-256) of the ELF file sections. This digest uses all ELF sections loaded in memory, but excludes the ELF header, the .SUNW_signature section, and the symbol table Extract the RSA signature (RSA-2048) from the .SUNW_signature section Extract the RSA public key modulus and public key exponent (65537) from the public key cert Calculate the expected digest as follows:     signaturepublicKeyExponent % publicKeyModulus Strip the PKCS#1 padding (most significant bytes) from the above. The padding is 0x00, 0x01, 0xff, 0xff, . . ., 0xff, 0x00. If the actual digest == expected digest, the ELF file is verified (OK). Further Information elfsign(1), pktool(1), and openssl(1) man pages. "Signed Solaris 10 Binaries?" blog by Darren Moffat (2005) shows how to use elfsign. "Simple CLI based CA on Solaris" blog by Darren Moffat (2008) shows how to set up a simple CA for use with self-signed certificates. "How to Create a Certificate by Using the pktool gencert Command" System Administration Guide: Security Services (available at docs.oracle.com)

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• SQLAuthority News – Public Training Classes In Hyderabad 12-14 May – Microsoft SQL Server 2005/2008

  - by pinaldave

  After successfully delivering many corporate trainings as well as the private training Solid Quality Mentors, India is launching the Public Training in Hyderabad for SQL Server 2008 and SharePoint 2010. This is going to be one of the most unique and one-of-a-kind events in India where Solid Quality Mentors are offering public classes. I will be leading the training on Microsoft SQL Server 2005/2008 Query Optimization & Performance Tuning. This intensive, 3-day course intends to give attendees an in-depth look at Query Optimization and Performance Tuning in SQL Server 2005 and 2008. Designed to prepare SQL Server developers and administrators for a transition into SQL Server 2005 or 2008, the course covers the best practices for a variety of essential tasks in order to maximize the performance. At the end of the course, there would be daily discussions about your real-world problems and find appropriate solutions. Note: Scroll down for course fees, discount, dates and location. Do not forget to take advantage of Discount code ‘SQLAuthority‘. The training premises are very well-equipped as they will be having 1:1 computers. Every participant will be provided with printed course materials. I will pick up your entire lunch tab and we will have lots of SQL talk together. The best participant will receive a special gift at the end of the course. Even though the quality of the material to be delivered together with the course will be of extremely high standard, the course fees are set at a very moderate rate. The fee for the course is INR 14,000/person for the whole 3-day convention. At the rate of 1 USD = 44 INR, this fee converts to less than USD 300. At this rate, it is totally possible to fly from anywhere from the world to India and take the training and still save handsome pocket money. It would be even better if you register using the discount code “SQLAuthority“, for you will instantly get an INR 3000 discount, reducing the total cost of the training to INR 11,000/person for whole 3 days course. This is a onetime offer and will not be available in the future. Please note that there will be a 10.3% service tax on course fees. To register, either send an email to [email protected] or call +91 95940 43399. Feel free to drop me an email at [email protected] for any additional information and clarification. Training Date and Time: May 12-14, 2010 10 AM- 6 PM. Training Venue: Abridge Solutions, #90/B/C/3/1, Ganesh GHR & MSY Plaza, Vittalrao Nagar, Near Image Hospital, Madhapur, Hyderabad – 500 081. The details of the course is as listed below. Day 1 : Strengthen the basics along with SQL Server 2005/2008 New Features Module 01: Subqueries, Ranking Functions, Joins and Set Operations Module 02: Table Expressions Module 03: TOP and APPLY Module 04: SQL Server 2008 Enhancements Day 2: Query Optimization & Performance Tuning 1 Module 05: Logical Query Processing Module 06: Query Tuning Module 07:  Introduction to the Query Processor Module 08:  Review of common query coding which causes poor performance Day 3: Query Optimization & Performance Tuning 2 Module 09:  SQL Server Indexing and index maintenance Module 10:  Plan Guides, query hints, UDFs, and Computed Columns Module 11:  Understanding SQL Server Execution Plans Module 12: Real World Index and Optimization Tips Download the complete PDF brochure. We are also going to have SharePoint 2010 training by Joy Rathnayake on 10-11 May. All the details for discount applies to the same as well. Reference : Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Training, SQLAuthority News, T SQL, Technology

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• Setting up a VPN connection to Amazon VPC - routing

  - by Keeno

  I am having some real issues setting up a VPN between out office and AWS VPC. The "tunnels" appear to be up, however I don't know if they are configured correctly. The device I am using is a Netgear VPN Firewall - FVS336GV2 If you see in the attached config downloaded from VPC (#3 Tunnel Interface Configuration), it gives me some "inside" addresses for the tunnel. When setting up the IPsec tunnels do I use the inside tunnel IP's (e.g. 169.254.254.2/30) or do I use my internal network subnet (10.1.1.0/24) I have tried both, when I tried the local network (10.1.1.x) the tracert stops at the router. When I tried with the "inside" ips, the tracert to the amazon VPC (10.0.0.x) goes out over the internet. this all leads me to the next question, for this router, how do I set up stage #4, the static next hop? What are these seemingly random "inside" addresses and where did amazon generate them from? 169.254.254.x seems odd? With a device like this, is the VPN behind the firewall? I have tweaked any IP addresses below so that they are not "real". I am fully aware, this is probably badly worded. Please if there is any further info/screenshots that will help, let me know. Amazon Web Services Virtual Private Cloud IPSec Tunnel #1 ================================================================================ #1: Internet Key Exchange Configuration Configure the IKE SA as follows - Authentication Method : Pre-Shared Key - Pre-Shared Key : --- - Authentication Algorithm : sha1 - Encryption Algorithm : aes-128-cbc - Lifetime : 28800 seconds - Phase 1 Negotiation Mode : main - Perfect Forward Secrecy : Diffie-Hellman Group 2 #2: IPSec Configuration Configure the IPSec SA as follows: - Protocol : esp - Authentication Algorithm : hmac-sha1-96 - Encryption Algorithm : aes-128-cbc - Lifetime : 3600 seconds - Mode : tunnel - Perfect Forward Secrecy : Diffie-Hellman Group 2 IPSec Dead Peer Detection (DPD) will be enabled on the AWS Endpoint. We recommend configuring DPD on your endpoint as follows: - DPD Interval : 10 - DPD Retries : 3 IPSec ESP (Encapsulating Security Payload) inserts additional headers to transmit packets. These headers require additional space, which reduces the amount of space available to transmit application data. To limit the impact of this behavior, we recommend the following configuration on your Customer Gateway: - TCP MSS Adjustment : 1387 bytes - Clear Don't Fragment Bit : enabled - Fragmentation : Before encryption #3: Tunnel Interface Configuration Your Customer Gateway must be configured with a tunnel interface that is associated with the IPSec tunnel. All traffic transmitted to the tunnel interface is encrypted and transmitted to the Virtual Private Gateway. The Customer Gateway and Virtual Private Gateway each have two addresses that relate to this IPSec tunnel. Each contains an outside address, upon which encrypted traffic is exchanged. Each also contain an inside address associated with the tunnel interface. The Customer Gateway outside IP address was provided when the Customer Gateway was created. Changing the IP address requires the creation of a new Customer Gateway. The Customer Gateway inside IP address should be configured on your tunnel interface. Outside IP Addresses: - Customer Gateway : 217.33.22.33 - Virtual Private Gateway : 87.222.33.42 Inside IP Addresses - Customer Gateway : 169.254.254.2/30 - Virtual Private Gateway : 169.254.254.1/30 Configure your tunnel to fragment at the optimal size: - Tunnel interface MTU : 1436 bytes #4: Static Routing Configuration: To route traffic between your internal network and your VPC, you will need a static route added to your router. Static Route Configuration Options: - Next hop : 169.254.254.1 You should add static routes towards your internal network on the VGW. The VGW will then send traffic towards your internal network over the tunnels. IPSec Tunnel #2 ================================================================================ #1: Internet Key Exchange Configuration Configure the IKE SA as follows - Authentication Method : Pre-Shared Key - Pre-Shared Key : --- - Authentication Algorithm : sha1 - Encryption Algorithm : aes-128-cbc - Lifetime : 28800 seconds - Phase 1 Negotiation Mode : main - Perfect Forward Secrecy : Diffie-Hellman Group 2 #2: IPSec Configuration Configure the IPSec SA as follows: - Protocol : esp - Authentication Algorithm : hmac-sha1-96 - Encryption Algorithm : aes-128-cbc - Lifetime : 3600 seconds - Mode : tunnel - Perfect Forward Secrecy : Diffie-Hellman Group 2 IPSec Dead Peer Detection (DPD) will be enabled on the AWS Endpoint. We recommend configuring DPD on your endpoint as follows: - DPD Interval : 10 - DPD Retries : 3 IPSec ESP (Encapsulating Security Payload) inserts additional headers to transmit packets. These headers require additional space, which reduces the amount of space available to transmit application data. To limit the impact of this behavior, we recommend the following configuration on your Customer Gateway: - TCP MSS Adjustment : 1387 bytes - Clear Don't Fragment Bit : enabled - Fragmentation : Before encryption #3: Tunnel Interface Configuration Outside IP Addresses: - Customer Gateway : 217.33.22.33 - Virtual Private Gateway : 87.222.33.46 Inside IP Addresses - Customer Gateway : 169.254.254.6/30 - Virtual Private Gateway : 169.254.254.5/30 Configure your tunnel to fragment at the optimal size: - Tunnel interface MTU : 1436 bytes #4: Static Routing Configuration: Static Route Configuration Options: - Next hop : 169.254.254.5 You should add static routes towards your internal network on the VGW. The VGW will then send traffic towards your internal network over the tunnels. EDIT #1 After writing this post, I continued to fiddle and something started to work, just not very reliably. The local IPs to use when setting up the tunnels where indeed my network subnets. Which further confuses me over what these "inside" IP addresses are for. The problem is, results are not consistent what so ever. I can "sometimes" ping, I can "sometimes" RDP using the VPN. Sometimes, Tunnel 1 or Tunnel 2 can be up or down. When I came back into work today, Tunnel 1 was down, so I deleted it and re-created it from scratch. Now I cant ping anything, but Amazon AND the router are telling me tunnel 1/2 are fine. I guess the router/vpn hardware I have just isnt up to the job..... EDIT #2 Now Tunnel 1 is up, Tunnel 2 is down (I didn't change any settings) and I can ping/rdp again. EDIT #3 Screenshot of route table that the router has built up. Current state (tunnel 1 still up and going string, 2 is still down and wont re-connect)

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• Puppet's automatically generated certificates failing

  - by gparent

  I am running a default configuration of Puppet on Debian Squeeze 6.0.4. The server's FQDN is master.example.com. The client's FQDN is client.example.com. I am able to contact the puppet master and send a CSR. I sign it using puppetca -sa but the client will still not connect. Date of both machines is within 2 seconds of Tue Apr 3 20:59:00 UTC 2012 as I wrote this sentence. This is what appears in /var/log/syslog: Apr 3 17:03:52 localhost puppet-agent[18653]: Reopening log files Apr 3 17:03:52 localhost puppet-agent[18653]: Starting Puppet client version 2.6.2 Apr 3 17:03:53 localhost puppet-agent[18653]: Could not retrieve catalog from remote server: SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B: certificate verify failed Apr 3 17:03:53 localhost puppet-agent[18653]: Using cached catalog Apr 3 17:03:53 localhost puppet-agent[18653]: Could not retrieve catalog; skipping run Here is some interesting output: OpenSSL client test: client:~# openssl s_client -host master.example.com -port 8140 -cert /var/lib/puppet/ssl/certs/client.example.com.pem -key /var/lib/puppet/ssl/private_keys/client.example.com.pem -CAfile /var/lib/puppet/ssl/certs/ca.pem CONNECTED(00000003) depth=1 /CN=Puppet CA: master.example.com verify return:1 depth=0 /CN=master.example.com verify error:num=7:certificate signature failure verify return:1 depth=0 /CN=master.example.com verify return:1 18509:error:1409441B:SSL routines:SSL3_READ_BYTES:tlsv1 alert decrypt error:s3_pkt.c:1102:SSL alert number 51 18509:error:140790E5:SSL routines:SSL23_WRITE:ssl handshake failure:s23_lib.c:188: client:~# master's certificate: root@master:/etc/puppet# openssl x509 -text -noout -in /etc/puppet/ssl/certs/master.example.com.pem Certificate: Data: Version: 3 (0x2) Serial Number: 2 (0x2) Signature Algorithm: sha1WithRSAEncryption Issuer: CN=Puppet CA: master.example.com Validity Not Before: Apr 2 20:01:28 2012 GMT Not After : Apr 2 20:01:28 2017 GMT Subject: CN=master.example.com Subject Public Key Info: Public Key Algorithm: rsaEncryption RSA Public Key: (1024 bit) Modulus (1024 bit): 00:a9:c1:f9:4c:cd:0f:68:84:7b:f4:93:16:20:44: 7a:2b:05:8e:57:31:05:8e:9c:c8:08:68:73:71:39: c1:86:6a:59:93:6e:53:aa:43:11:83:5b:2d:8c:7d: 54:05:65:c1:e1:0e:94:4a:f0:86:58:c3:3d:4f:f3: 7d:bd:8e:29:58:a6:36:f4:3e:b2:61:ec:53:b5:38: 8e:84:ac:5f:a3:e3:8c:39:bd:cf:4f:3c:ff:a9:65: 09:66:3c:ba:10:14:69:d5:07:57:06:28:02:37:be: 03:82:fb:90:8b:7d:b3:a5:33:7b:9b:3a:42:51:12: b3:ac:dd:d5:58:69:a9:8a:ed Exponent: 65537 (0x10001) X509v3 extensions: X509v3 Basic Constraints: critical CA:FALSE Netscape Comment: Puppet Ruby/OpenSSL Internal Certificate X509v3 Key Usage: critical Digital Signature, Key Encipherment X509v3 Subject Key Identifier: 8C:2F:14:84:B6:A1:B5:0C:11:52:36:AB:E5:3F:F2:B9:B3:25:F3:1C X509v3 Extended Key Usage: critical TLS Web Server Authentication, TLS Web Client Authentication Signature Algorithm: sha1WithRSAEncryption 7b:2c:4f:c2:76:38:ab:03:7f:c6:54:d9:78:1d:ab:6c:45:ab: 47:02:c7:fd:45:4e:ab:b5:b6:d9:a7:df:44:72:55:0c:a5:d0: 86:58:14:ae:5f:6f:ea:87:4d:78:e4:39:4d:20:7e:3d:6d:e9: e2:5e:d7:c9:3c:27:43:a4:29:44:85:a1:63:df:2f:55:a9:6a: 72:46:d8:fb:c7:cc:ca:43:e7:e1:2c:fe:55:2a:0d:17:76:d4: e5:49:8b:85:9f:fa:0e:f6:cc:e8:28:3e:8b:47:b0:e1:02:f0: 3d:73:3e:99:65:3b:91:32:c5:ce:e4:86:21:b2:e0:b4:15:b5: 22:63 root@master:/etc/puppet# CA's certificate: root@master:/etc/puppet# openssl x509 -text -noout -in /etc/puppet/ssl/certs/ca.pem Certificate: Data: Version: 3 (0x2) Serial Number: 1 (0x1) Signature Algorithm: sha1WithRSAEncryption Issuer: CN=Puppet CA: master.example.com Validity Not Before: Apr 2 20:01:05 2012 GMT Not After : Apr 2 20:01:05 2017 GMT Subject: CN=Puppet CA: master.example.com Subject Public Key Info: Public Key Algorithm: rsaEncryption RSA Public Key: (1024 bit) Modulus (1024 bit): 00:b5:2c:3e:26:a3:ae:43:b8:ed:1e:ef:4d:a1:1e: 82:77:78:c2:98:3f:e2:e0:05:57:f0:8d:80:09:36: 62:be:6c:1a:21:43:59:1d:e9:b9:4d:e0:9c:fa:09: aa:12:a1:82:58:fc:47:31:ed:ad:ad:73:01:26:97: ef:d2:d6:41:6b:85:3b:af:70:00:b9:63:e9:1b:c3: ce:57:6d:95:0e:a6:d2:64:bd:1f:2c:1f:5c:26:8e: 02:fd:d3:28:9e:e9:8f:bc:46:bb:dd:25:db:39:57: 81:ed:e5:c8:1f:3d:ca:39:cf:e7:f3:63:75:f6:15: 1f:d4:71:56:ed:84:50:fb:5d Exponent: 65537 (0x10001) X509v3 extensions: X509v3 Basic Constraints: critical CA:TRUE Netscape Comment: Puppet Ruby/OpenSSL Internal Certificate X509v3 Key Usage: critical Certificate Sign, CRL Sign X509v3 Subject Key Identifier: 8C:2F:14:84:B6:A1:B5:0C:11:52:36:AB:E5:3F:F2:B9:B3:25:F3:1C Signature Algorithm: sha1WithRSAEncryption 1d:cd:c6:65:32:42:a5:01:62:46:87:10:da:74:7e:8b:c8:c9: 86:32:9e:c2:2e:c1:fd:00:79:f0:ef:d8:73:dd:7e:1b:1a:3f: cc:64:da:a3:38:ad:49:4e:c8:4d:e3:09:ba:bc:66:f2:6f:63: 9a:48:19:2d:27:5b:1d:2a:69:bf:4f:f4:e0:67:5e:66:84:30: e5:85:f4:49:6e:d0:92:ae:66:77:50:cf:45:c0:29:b2:64:87: 12:09:d3:10:4d:91:b6:f3:63:c4:26:b3:fa:94:2b:96:18:1f: 9b:a9:53:74:de:9c:73:a4:3a:8d:bf:fa:9c:c0:42:9d:78:49: 4d:70 root@master:/etc/puppet# Client's certificate: client:~# openssl x509 -text -noout -in /var/lib/puppet/ssl/certs/client.example.com.pem Certificate: Data: Version: 3 (0x2) Serial Number: 3 (0x3) Signature Algorithm: sha1WithRSAEncryption Issuer: CN=Puppet CA: master.example.com Validity Not Before: Apr 2 20:01:36 2012 GMT Not After : Apr 2 20:01:36 2017 GMT Subject: CN=client.example.com Subject Public Key Info: Public Key Algorithm: rsaEncryption RSA Public Key: (1024 bit) Modulus (1024 bit): 00:ae:88:6d:9b:e3:b1:fc:47:07:d6:bf:ea:53:d1: 14:14:9b:35:e6:70:43:e0:58:35:76:ac:c5:9d:86: 02:fd:77:28:fc:93:34:65:9d:dd:0b:ea:21:14:4d: 8a:95:2e:28:c9:a5:8d:a2:2c:0e:1c:a0:4c:fa:03: e5:aa:d3:97:98:05:59:3c:82:a9:7c:0e:e9:df:fd: 48:81:dc:33:dc:88:e9:09:e4:19:d6:e4:7b:92:33: 31:73:e4:f2:9c:42:75:b2:e1:9f:d9:49:8c:a7:eb: fa:7d:cb:62:22:90:1c:37:3a:40:95:a7:a0:3b:ad: 8e:12:7c:6e:ad:04:94:ed:47 Exponent: 65537 (0x10001) X509v3 extensions: X509v3 Basic Constraints: critical CA:FALSE Netscape Comment: Puppet Ruby/OpenSSL Internal Certificate X509v3 Key Usage: critical Digital Signature, Key Encipherment X509v3 Subject Key Identifier: 8C:2F:14:84:B6:A1:B5:0C:11:52:36:AB:E5:3F:F2:B9:B3:25:F3:1C X509v3 Extended Key Usage: critical TLS Web Server Authentication, TLS Web Client Authentication Signature Algorithm: sha1WithRSAEncryption 33:1f:ec:3c:91:5a:eb:c6:03:5f:a1:58:60:c3:41:ed:1f:fe: cb:b2:40:11:63:4d:ba:18:8a:8b:62:ba:ab:61:f5:a0:6c:0e: 8a:20:56:7b:10:a1:f9:1d:51:49:af:70:3a:05:f9:27:4a:25: d4:e6:88:26:f7:26:e0:20:30:2a:20:1d:c4:d3:26:f1:99:cf: 47:2e:73:90:bd:9c:88:bf:67:9e:dd:7c:0e:3a:86:6b:0b:8d: 39:0f:db:66:c0:b6:20:c3:34:84:0e:d8:3b:fc:1c:a8:6c:6c: b1:19:76:65:e6:22:3c:bf:ff:1c:74:bb:62:a0:46:02:95:fa: 83:41 client:~#

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• Books or resources for high-loaded sites.

  - by Alex

  Currently I'm developing high-loaded financial portal(we use LAMP to run our project). There are great number of incoming data to be processed and stored. So optimization tasks become very important for us. Could you suggest books, articles or resources, that discover optimization questions (especially bboks). NOTE: At the moment I'm reading great book High Performance MySQL, but besides I want to know other facilities of optimization.

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• Depth interpolation for z-buffer, with scanline

  - by Twodordan

  I have to write my own software 3d rasterizer, and so far I am able to project my 3d model made of triangles into 2d space: I rotate, translate and project my points to get a 2d space representation of each triangle. Then, I take the 3 triangle points and I implement the scanline algorithm (using linear interpolation) to find all points[x][y] along the edges(left and right) of the triangles, so that I can scan the triangle horizontally, row by row, and fill it with pixels. This works. Except I have to also implement z-buffering. This means that knowing the rotated&translated z coordinates of the 3 vertices of the triangle, I must interpolate the z coordinate for all other points I find with my scanline algorithm. The concept seems clear enough, I first find Za and Zb with these calculations: var Z_Slope = (bottom_point_z - top_point_z) / (bottom_point_y - top_point_y); var Za = top_point_z + ((current_point_y - top_point_y) * Z_Slope); Then for each Zp I do the same interpolation horizontally: var Z_Slope = (right_z - left_z) / (right_x - left_x); var Zp = left_z + ((current_point_x - left_x) * Z_Slope); And of course I add to the zBuffer, if current z is closer to the viewer than the previous value at that index. (my coordinate system is x: left - right; y: top - bottom; z: your face - computer screen;) The problem is, it goes haywire. The project is here and if you select the "Z-Buffered" radio button, you'll see the results... (note that the rest of the options before "Z-Buffered" use the Painter's algorithm to correctly order the triangles. I also use the painter's algorithm -only- to draw the wireframe in "Z-Buffered" mode for debugging purposes) PS: I've read here that you must turn the z's into their reciprocals (meaning z = 1/z) before you interpolate. I tried that, and it appears that there's no change. What am I missing? (could anyone clarify, precisely where you must turn z into 1/z and where to turn it back?)

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• Do I need path finding to make AI avoid obstacles?

  - by yannicuLar

  How do you know when a path-finding algorithm is really needed? There are contexts, where you just want to improve AI navigation to avoid an object, like a space -ship that won't crash on a planet or a car that already knows where to steer, but needs small corrections to avoid a road bump. As I've seen on similar posts, the obvious solution is to implement some path-finding algorithm, most likely like A*, and let your AI-controlled object to navigate through the path. Now, I have the necessary skills to implement a path-finding algorithm, and I'm not being lazy here, but I'm still a bit skeptical on if this is really needed. I have the impression that path-finding is appropriate to navigate through a maze, or picking a path when there are many alternatives. But in obstacle avoidance, when you do know the path, but need to make slight corrections, is path finding really necessary? Even when the obstacles are too sparse or small ? I mean, in real life, when you're driving and notice a bump on the road, you will just have to pick between steering a bit on the left (and have the bump on your right side) or the other way around. You will not consider stopping, or going backwards. A path finding would be appropriate when you need to pick a route through the city, right ? So, are there any other methods to help AI navigation, except path-finding? And if there are, how do you know when path-fining is the appropriate algorithm ? Thanks for any thoughts

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• A Cautionary Tale About Multi-Source JNDI Configuration

  - by scott.s.nelson(at)oracle.com

  Here's a bit of fun with WebLogic JDBC configurations.  I ran into this issue after reading that p13nDataSource and cgDataSource-NonXA should not be configured as multi-source. There were some issues changing them to use the basic JDBC connection string and when rolling back to the bad configuration the server went "Boom".  Since one purpose behind this blog is to share lessons learned, I just had to post this. If you write your descriptors manually (as opposed to generating them using the WLS console) and put a comma-separated list of JNDI addresses like this: <jdbc-data-source-params> <jndi-name>weblogic.jdbc.jts.commercePool,contentDataSource, contentVersioningDataSource,portalFrameworkPool</jndi-name> <algorithm-type>Load-Balancing</algorithm-type> <data-source-list>portalDataSource-rac0,portalDataSource-rac1</data-source-list> <failover-request-if-busy>false</failover-request-if-busy> </jdbc-data-source-params> so long as the first address resolves, it will still work. Sort of.  If you call this connection to do an update, only one node of the RAC instance is updated. Other wonderful side-effects include the server refusing to start sometimes. The proper way to list the JNDI sources is one per node, like this: <jdbc-data-source-params> <jndi-name>weblogic.jdbc.jts.commercePool</jndi-name> <jndi-name>contentDataSource</jndi-name> <jndi-name>contentVersioningDataSource</jndi-name> <jndi-name>portalFrameworkPool</jndi-name> <algorithm-type>Load-Balancing</algorithm-type> <data-source-list>portalDataSource-rac0, portalDataSource-rac1, portalDataSource-rac2 </data-source-list> <failover-request-if-busy>false</failover-request-if-busy> </jdbc-data-source-params>(Props to Sandeep Seshan for locating the root cause)

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• A new mission statement for my school's algorithms class

  - by Eric Fode

  The teacher at Eastern Washington University that is now teaching the algorithms course is new to eastern and as a result the course has changed drastically mostly in the right direction. That being said I feel that the class could use a more specific, and industry oriented (since that is where most students will go, though suggestions for an academia oriented class are also welcome) direction, having only worked in industry for 2 years I would like the community's (a wider and much more collectively experienced and in the end plausibly more credible) opinion on the quality of this as a statement for the purpose an algorithms class, and if I am completely off target your suggestion for the purpose of a required Jr. level Algorithms class that is standalone (so no other classes focusing specifically on algorithms are required). The statement is as follows: The purpose of the algorithms class is to do three things: Primarily, to teach how to learn, do basic analysis, and implement a given algorithm found outside of the class. Secondly, to teach the student how to model a problem in their mind so that they can find a an existing algorithm or have a direction to start the development of a new algorithm. Third, to overview a variety of algorithms that exist and to deeply understand and analyze one algorithm in each of the basic algorithmic design strategies: Divide and Conquer, Reduce and Conquer, Transform and Conquer, Greedy, Brute Force, Iterative Improvement and Dynamic Programming. The Question in short is: do you agree with this statement of the purpose of an algorithms course, so that it would be useful in the real world, if not what would you suggest?

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• Find points whose pairwise distances approximate a given distance matrix

  - by Stephan Kolassa

  Problem. I have a symmetric distance matrix with entries between zero and one, like this one: D = ( 0.0 0.4 0.0 0.5 ) ( 0.4 0.0 0.2 1.0 ) ( 0.0 0.2 0.0 0.7 ) ( 0.5 1.0 0.7 0.0 ) I would like to find points in the plane that have (approximately) the pairwise distances given in D. I understand that this will usually not be possible with strictly correct distances, so I would be happy with a "good" approximation. My matrices are smallish, no more than 10x10, so performance is not an issue. Question. Does anyone know of an algorithm to do this? Background. I have sets of probability densities between which I calculate Hellinger distances, which I would like to visualize as above. Each set contains no more than 10 densities (see above), but I have a couple of hundred sets. What I did so far. I did consider posting at math.SE, but looking at what gets tagged as "geometry" there, it seems like this kind of computational geometry question would be more on-topic here. If the community thinks this should be migrated, please go ahead. This looks like a straightforward problem in computational geometry, and I would assume that anyone involved in clustering might be interested in such a visualization, but I haven't been able to google anything. One simple approach would be to randomly plonk down points and perturb them until the distance matrix is close to D, e.g., using Simulated Annealing, or run a Genetic Algorithm. I have to admit that I haven't tried that yet, hoping for a smarter way. One specific operationalization of a "good" approximation in the sense above is Problem 4 in the Open Problems section here, with k=2. Now, while finding an algorithm that is guaranteed to find the minimum l1-distance between D and the resulting distance matrix may be an open question, it still seems possible that there at least is some approximation to this optimal solution. If I don't get an answer here, I'll mail the gentleman who posed that problem and ask whether he knows of any approximation algorithm (and post any answer I get to that here).

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• SEO Courses - Tips and Techniques to Enhance Visibility

  Search Engine Optimization (SEO) is the process of optimizing a web site to achieve a higher ranking when a search engine looks for web pages based on particular word or phrase. The SEO courses empower you with the wherewithal to successfully set up and run an optimization program.

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• Few Steps For Making Your Website SEO Friendly

  Currently going by the dynamics of the internet every web designer of class is expected to be acquainted with or have a basic working knowledge of search engine optimization tools. Web promotion as an optimization tool for enhancing increased traffic to a given site is one skill web designers just like online marketers require in their respective fields to conquer the market.

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• My Rant About the SEO Specialist

  Clients wishing to avail of search engine optimization services will have an important choice to make. They can choose between hiring SEO specialists or SEO generalists to provide the services they need. SEO specialists are technicians who concentrate on specific aspects of search engine optimization while generalists will take on all aspects of it. This article looks into the pros and cons of employing these service providers.

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• Five Query Optimizations in MySQL

  Query optimization is an often overlooked part of applications. Sean Hull encourages at least some attention to query optimization up front and helps you identify some of the more common optimizations you may run across.

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