Thursday, 24 March 2011

Interesting CAPTCHA

We easily overlook obvious and simple solutions. Many websites use CAPTCHA to authenticate users and differentiate them from programs. However, programs are evolving and they are cracking the CAPTCHA visual test for authentication.

Recently, I came across a website that uses CAPTCHA to fool programs. Here is a screenshot explaining how.

Tuesday, 8 March 2011

The Beauty of a Gentoo installation

I have installed various linux distributions so far but Gentoo installation has an unmatched beauty to it. It is special because you can stop the installation and resume it at will. You just need to chroot back in if you have not completed the base system installation. Once the base system is installed, you can keep adding features at your pace and suiting your internet speed.

Unlike other distributions, Gentoo offers very fine-grained control over the packages you install and what features those packages have enabled. This is done using USE flags.

If you are looking a graphical installer that does its job without asking you much, this is not for you; but if you want robust control with proper dependency checking and stability, Gentoo is the right choice for you.

While other distributions have trouble connecting to the internet from their install environments, Gentoo minimal install environment had Intel Wireless microcode (iwl3945-ucode) and I could connect to a WPA network and do the installation.

Support on #gentoo sets Gentoo apart from every other distribution. I have solved problems of other distributions on this channel. Every time you have an issue, you can find someone here to help you out.

The beauty of the installation process lies in the freedom and the host of options that it allows you.

Sunday, 6 March 2011

Connecting to WPA networks

Wireless networks using WEP keys are not very secure. WPA keys should be preferred over WEP keys. To connect to a wireless network on linux, first store the passphrase in a configuration file with the following command:

wpa_passphrase "<your essid>" "<your passphrase>" > /etc/wpa_supplicant.conf

Set up WPA handshaking using

wpa_supplicant -Dwext -iwlan0 -B -c/etc/wpa_supplicant.conf

The option -Dwext specifies that generic linux wireless drivers should be used. The -B flag tells wpa_supplicant to work in the background. The -iwlan0 option specifies wlan0 as the interface for communication. Now set up dhcp client on wlan0 using

dhcpcd wlan0

Thursday, 3 March 2011

Robust Firefox

Today an interesting incident occurred which reassured by trust in Firefox's robustness. Well I was downloading gentoo minimal install image in Google Chrome and after 80mb, the download speed had gone down to some bytes per second. When I started a parallel fresh download, I was getting a speed of about 60 kbps. So, I decided to try and get Chrome download the rest of the original file at about 50 - 60 kbps. I tried the following procedure:

- copy the install*.chrdownload file (i.e. the temporary file into which the file was being downloaded) into some other folder
- cancel the download
- start a fresh download
- pause it
- overwrite the new .chrdowload file with the old one

However, this trick did not work with Chrome. It was still downloading more than 100 mb as if it were the fresh download.

I opened up Firefox and applied the same procedure except for renaming the .chrdownload file to .part file and Firefox intelligently downloaded only what remained of the file completing the download in minutes.