Bala-Krishna

What is Cryptography

Bala Krishna — Sun, 28 Jun 2009 12:28:46 +0000

Cryptography is the process of transforming digital information into an unintelligible form so that it can be sent over unsafe channel of communication. The transformed data called cipher text that is in the form that nobody can understand. The transformation process handled by a data key. This key required to transform cipher text into original state. The stage of conversion of the digital data into unintelligible form is called Encrypting or Encoding. Reconverting the encoded data back into the original form by the authorized person using the appropriate key is called decrypting or decoding. Below is basic diagram explaining encryption and decryption process.

ENCRYPTION:

Ascii Text Or Data –> Algorithm –> Secret Key –> Cipher Text

DECRYPTION:

Cipher Text –> Algorithm –> Secret Key –> Original Data

Encryption Algorithm

Transposition Cipher
Code System
Data Encryption Standard (DES)
RSA Approach

This post is brought to you by Bala Krishna Tech Update Blog.

How To Unintruppted/Unattended Complete Folder Copy With DOS

Bala Krishna — Sun, 17 May 2009 16:07:11 +0000

The copy command is primary command available in Dos as well as Linux operating system for organizing and making copies of files. Working with dos is relatively faster than working in windows environment. However copy command have several drawback. You can not copy complete disk or a folder with files and sub-directory in folder with copy command. Moreover copy process will be halted if problem persist in copying files in destination location. Even windows explorer does not ask to retry or skip file in case of problem. Linux is better in this case, at-least Linux ask user to retry, halt or skip file.

Dos support external XCOPY command for this purpose and support numerous switches. I use following command with switches to create a replica of one location.

C:/> xcopy d:\*.* h: /s /c /h

This command copy all files in D: drive to H: drive. The /s switch used to copy all directory and sub directories. /c used to continue copy with rest of directories and files even if error occurred. /h used to copy hidden and system files. Use /Y to overwrite file without prompt if file already exist in the destination directory.

xcopy support following switches that you can use for your own conveyance.

/A	Copies only files with the archive attribute set, doesn’t change the attribute.
/M	Copies only files with the archive attribute set, turns off the archive attribute.
/D:m-d-y	Copies files changed on or after the specified date. If no date is given, copies only those files whose source time is newer than the destination time.
/P	Prompts you before creating each destination file.
/S	Copies directories and subdirectories except empty ones.
/E	Copies directories and subdirectories, including empty ones. Same as /S /E. May be used to modify /T.
/V	Verifies each new file.
/W	Prompts you to press a key before copying.
/C	Continues copying even if errors occur.
/I	If destination does not exist and copying more than one file, assumes that destination must be a directory.
/Q	Does not display file names while copying.
/F	Displays full source and destination file names while copying.
/L	Displays files that would be copied.
/H	Copies hidden and system files also.
/R	Overwrites read-only files.
/T	Creates directory structure, but does not copy files. Does not include empty directories or subdirectories. /T /E includes empty directories and subdirectories.
/U	Copies only files that already exist in destination.
/K	Copies attributes. Normal Xcopy will reset read-only attributes.
/N	Copies using the generated short names.
/O	Copies file ownership and ACL information.
/X	Copies file audit settings (implies /O).
/Y	Suppresses prompting to confirm you want to overwrite an existing destination file.
/-Y	Causes prompting to confirm you want to overwrite an existing destination file.
/Z	Copies networked files in restartable mode.

FileZilla Disconnect Problem Fix

Bala Krishna — Sun, 12 Apr 2009 07:19:37 +0000

FileZilla is great open source ftp software. Everyone using it likes its design and user friendly interface. However, it lacks multiple ftp session features. This is very required feature for the users who want to connect to multiple ftp sites at the same time without disconnecting current session. I hope multiple ftp session will be added in upcoming releases. I personally use multiple instances of FileZilla when i want to connect with more then two website at the same time. You can also use this until we get this feature added in FileZill future releases.

Lets come to disconnect problem. The problem is big pain for the user who don’t want to away from FileZilla. Here is the work around i did to overcome this issue.

Go to FileZill Settings (Edit – > Settings)
Select Connection From Left Panel
Check “Send FTP Keep Alive Commands” Check Box
Again Select Transfers From Left Panel
Set Timeout to Zero(0) Seconds

MySQL Too Many Connections Error Problem & Fix

Bala Krishna — Sun, 01 Mar 2009 07:22:54 +0000

If you are getting� Too many connections error when you try to open your website in browser, It means all available connection used by other script or mysql process. Number of connection to mysql server determined by setting in mysql conf� file.� By default,� it is 151� for MySQL 5.x and 100 for MySQL 4.x.� To change setting, open mysql conf file. In Linux it can be found (/etc/my.cnf) and in windows within installation folder. Find max_connections setting under [mysqld] section. This setting must be within [mysqld] section. Change setting which is suitable to you.

[mysqld]
max_connections=200

There are several reason that cause server to raise this error:

Persistent Connections: This is common cause of this error. If script uses persisit connection and script does� not close connection even if script terminates. To avoid this problem, try using mysql_connect() instead of mysql_pconnect(). Check this setting in third party script such as osCommerce. You can turn off this setting in php.ini file. Script using persist connection will use non-persistent connection without any warning or error if persistence connection disabled.

Server administrators can disable persistent connections for PHP scripts in php.ini file:

[MySQL]
; Allow or prevent persistent links.
mysql.allow_persistent=Off

Lower MySQL Connect Timeout: Check your mysql connect timeout setting. By default it is 60 seconds and php setting lowering below the dafault setting.

For example: following setting in .htaccess php_value mysql.connect_timeout 25

osCommerce� Setting:

The osCommerce setting mentioned by ?varo is in the catalog/includes/configure.php file:

define(’USE_PCONNECT’, ‘false’); // use persistent connections?

It defaults to true, so mysql_pconnect() is used, and you get the error message “Warning: mysql_pconnect(): Too many connections …” Change to false for mysql_connect() to be used.

Dos Directory Commands With Switches

Bala Krishna — Sat, 28 Feb 2009 13:00:26 +0000

Dos directory command display files and directories in the current directory. If� information will more than 24 rows then information will scroll and you can see only last 24 rows information. Dos directory command support various switches to filter and format results.

Dir/p - Display directories and files in the current directory page wise. If� list is in more than 24 rows then a message “Press any key to continue” display to see list on next page.

Dir/w – Display the files and directories in 5 coulmns. Directory will display in [] brackets to standout.

Dir/l – Display files and directories in lower case.

Dir/ad – Display only directories.

Dir/od – Display the files and directory in date wise ascending order.

Dir/o-d – Display the files and directory in date wise descending order.

Dir/os – Display the files and directory in size wise ascending order.

Dir/o-s – Display the files and directory in size wise descending order.

Dir/oe - Display the files and directory in extension wise ascending order.

Dir/o-e – Display the files and directory in extension wise descending order.

Dir/on - Display the files and directory in alphabetic ascending order.

Dir/o-n – Display the files and directory in alphabetic descending order.

Dir/s – Find the file in directory and sub-directories and display path of file.

Google Strange Results – Adsense Domain Can Harm Your Computer

Bala Krishna — Sat, 31 Jan 2009 20:30:12 +0000

I usually open adsense by typing adsense keyword in the search box rather then typing in browser address bar. Today strange behavior of google search result have been noticed. Search using key phrased “Google Adsense” result me to show google adsense on top of the result. The result appear with label “This site may harm your computer”. I guess this is due to false human update by StopBadware.org. Google uses StopBadware.org to flag search result that may harm visitor computer.

See screen shot below: (Click on the image for full view)

Wordpress.TV – New Addition to Wordpress Family

Bala Krishna — Sat, 17 Jan 2009 20:42:32 +0000

Wordpress announced new Wordpress.TV where you can find all wordpress resources in audio visual form. You can find all WordCamp video, slideshows of presentation created by wordpress team and other wordpress experts, and interviews with media and fellow bloggers.

Wordpress.TV included several handy how-to tutorial video and more be in pipeline in future. You can request to add an audio visual resource if you find should be added on wordpress.tv.� I can also request if something missing and should be on site for wordpress community. Below is introductory video showing brief overview of the site.

TeaShark Mobile Browser

Bala Krishna — Sat, 17 Jan 2009 06:29:09 +0000

TeaShark is new full site mobile browser and can be a substitute for Opera Mini.� Still TeaShark� does not support the Blackberry, PalmOS/Windows Mobile based phones. A lot of improvement has to come with this mobile browser. This mobile browser is available in both .jar and .jad version.

TecchShark has many useful features like desktop browser that other mobile browser do not support. Some nice features at a glance.

Ability to render full web page just like your desktop browser.
4 way navigation support with navigation key or joystick key. This feature is customizable according to your need.
Two level zoom for fine reading and to smooth move from one section to another.
Landscape view by rotating website 90 degree. Allow you to surf better then portrait view.
TeaShark support multiple tab feature just like IE and Firefox in your desktop. Enable you to surf much convent then other browser.� You can open multiple site without closing current site.
TeaShark can save last session like firefox desktop browsers.� So you need not to worry about losing what you were browsering.
Built-in RSS Reader and much more.

How to use

Download TeaShark v. 419. It can be installed on most available handsets.
Open it from your mobile phone and select your preferred GPRS access point.
Open any site in TeaShark browser. First time it may initialize and take little longer time then usual.

How to disable wordpress version upgrade nag message

Bala Krishna — Sat, 17 Jan 2009 05:46:48 +0000

Wordpress has inbuilt latest version upgrade function to notify user about the new release. You should keep track of new release and upgrade your wordpress installation on time if you disable wordpress upgrade notification. It is just easy as you install new plugin on your wp installation

Click on the link below to download wordpress plugin
http://wordpress.org/extend/plugins/disable-wordpress-core-update/

Happy New Year 2009

Bala Krishna — Thu, 01 Jan 2009 04:51:20 +0000