RSA encryption in iOS and decrypt it using PHP

I’ve been suffer for few weeks on RSA encryption in iOS. Now I would like to share the way of doing this.

First, generate a key-pair using SSL.

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Ajax change dropdown list value with jQuery

A typical example for this is Country and State/Province.

You may have seen some website that provide such a dropdown list. When you change the Country, the State will be reloaded.

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Generate a random string with JavaScript

In order to generate a random string, we must first specify length of string and character set

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function generateRandom(lengthOfString, charset) {
// The scope of the character
if(charset == null) charset = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890';

var rand = '';

while(lengthOfString > 0) {
/*
since the index of char is start from 0, so no need to +1 on the random number
we want the range from 0 - lengthOfString
*/
rand += charset.charAt(Math.floor(Math.random() * charset.length));
lengthOfString--;
}
return rand;
}

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Remove Macbuntu from Ubuntu 12.10

About a month ago, I follow the instruction from here installed some components to make my desktop like OS X.

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iOS: UITabelView - didSelectRowAtIndexPath is not called

I had come across a problem which didSelectRowAtIndexPath doesn’t execute when I tap the cell.

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- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
NSLog(@"Successfully tapped");
UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];

[tableView deselectRowAtIndexPath:indexPath animated:YES];
}

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Crawling sequantial images with shell script

Let say you want to download from http://www.domain.com/images/, and you know that the images name is from 001 to 100

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How $_POST store array elements in PHP

Sometime we need an array form elements like this

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<input type="text" name="foo[]" value="a" />
<input type="text" name="foo[3]" value="b" />
<input type="text" name="foo[]" value="c" />
<input type="text" name="foo[7]" value="d" />

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OS X failed bundle install

When I try to setup octopress in OS X, I run bundle install, it always come out an error like:

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$ bundle install
Fetching gem metadata from http://rubygems.org/.......
Fetching gem metadata from http://rubygems.org/..
/Users/jslim/.rvm/gems/ruby-1.9.3-p327@global/gems/bundler-1.2.3/lib/bundler.rb:263: warning: Insecure world writable dir /usr/local/bin in PATH, mode 040777
Using rake (0.9.2.2)
Installing RedCloth (4.2.9) with native extensions
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

/Users/jslim/.rvm/rubies/ruby-1.9.3-p327/bin/ruby extconf.rb
checking for main() in -lc... *** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers. Check the mkmf.log file for more
details. You may need configuration options.

Provided configuration options:
--with-opt-dir
--without-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/Users/jslim/.rvm/rubies/ruby-1.9.3-p327/bin/ruby
--with-redcloth_scan-dir
--without-redcloth_scan-dir
--with-redcloth_scan-include
--without-redcloth_scan-include=${redcloth_scan-dir}/include
--with-redcloth_scan-lib
--without-redcloth_scan-lib=${redcloth_scan-dir}/lib
--with-clib
--without-clib
/Users/jslim/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:369:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.
from /Users/jslim/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:449:in `try_link0'
from /Users/jslim/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:464:in `try_link'
from /Users/jslim/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:607:in `try_func'
from /Users/jslim/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:833:in `block in have_library'
from /Users/jslim/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:778:in `block in checking_for'
from /Users/jslim/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:272:in `block (2 levels) in postpone'
from /Users/jslim/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:242:in `open'
from /Users/jslim/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:272:in `block in postpone'
from /Users/jslim/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:242:in `open'
from /Users/jslim/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:268:in `postpone'
from /Users/jslim/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:777:in `checking_for'
from /Users/jslim/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:828:in `have_library'
from extconf.rb:5:in `<main>'


Gem files will remain installed in /Users/jslim/.rvm/gems/ruby-1.9.3-p327/gems/RedCloth-4.2.9 for inspection.
Results logged to /Users/jslim/.rvm/gems/ruby-1.9.3-p327/gems/RedCloth-4.2.9/ext/redcloth_scan/gem_make.out
An error occurred while installing RedCloth (4.2.9), and Bundler cannot continue.
Make sure that `gem install RedCloth -v '4.2.9'` succeeds before bundling.

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ls command in OS X

ls by default in OS X has no --group-directories-first

Open up your terminal

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$ brew install coreutils

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Delete Linux partition from dual-boot (Windows 7 &amp; Linux)

First time I did this by just delete the partition via Disk Management on Windows 7. What is the consequence?

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