For good or bad many sites are now using CAPTCHAs to determine if visitor is human or computer program. Captcha presents a task – usually reading some distorted letters and writing them back to a form. This is considered to be hard for computer to do, so user must be human. To improve accessibility visual captchas are accompanied by audio captchas, where letters are spelled (usually with some background noise to make letters recognition more difficult) . However audio captchas are know to be easier to break. Inspired by this article [1] I created a python implementation of audio captchas decoding using commonly available libraries and with just a general knowledge of speech recognition technologies. Software is called adecaptcha and I tested it on couple of sites, where I got 99.5% accuracy of decoded letters for one site and 90% accuracy for other site (which has much distorted audio). Continue reading Decoding Audio Captchas in Python
Monthly Archives: August 2014
Running uWSGI for gevent enabled application
Gevent is a great library that uses greenlets (a Python co-routine library) to enable asynchronous I/O, while providing API that looks like normal synchronous API, so it’s easier to use and understand. The async magic is done automatically by Gevent, which is running an event loop on background and switching between coroutines as necessary.
This approach can be very useful for concurrent applications, which spend a lot of time in waiting for I/O. Like web applications – so Gevent is popular there. For certain type of workloads it can be quite useful – it can enable higher concurrency, while using less resources (greenlet is much lighter then thread or process). Continue reading Running uWSGI for gevent enabled application
Unity – adding unknown applications to Launcher/Dash
It’s described in numerous posts how to add new application to Unity so it’s searchable in Dash. Unity works with .desktop files, which define how applications should be launched from Unity – these files are located in /usr/share/applications (system wide definitions) or ~/.local/share/applications (user specifics application). So if you add well formated .desktop file to any of these locations Unity will be aware of it (may need to restart unity).
Recently I found one more interesting behavior of Unity – if you start unknown application from terminal it will appear in Launcher (in ‘Running applications’ section), Unity even makes some effort to find correct icon for it. Now you can lock it to Launcher (right click and chose ‘Lock to Launcher’ from menu). On background Unity creates new .desktop entry for this program in ~/.local/share/applications, so it can stay locked to Launcher in future. This new .desktop file contains title of the application from window title (in which application is running) executable path and parameters are taken from process properties, even icon path is stored if Unity was able to find one. And when you unlock application from launcher, .desktop file will still remain in users applications – so you can search it in Dash. So this approach can make adding new unknown application easier – just run, then lock and unlock from Launcher and you’ll have new entry in ~/.local/share/application. You can then edit it a bit manually to make it perfect and this is it.