CoWin Captcha Decode
CoWIN slots have opened for citizens in the age group of 18 to 44. However, 150 CoWIN slots are getting booked in a matter of seconds, which has become a cause of concern for thousands of people who are trying to book appointments for COVID-19 vaccinations in India. As soon as a slot is shown to be available, citizens trying to book the appointments are given the message that “This vaccination center is full for the mentioned date”.
After seeing this, I was planning to develop a Google Chrome Extension which could help users to automate the slot booking flow, but the captcha was impediment to complete this task.
So by doing some research I found that the captcha image is an SVG image and that clicked my mind.
What is SVG?
- SVG stands for Scalable Vector Graphics
- SVG is used to define vector-based graphics for the Web
- SVG defines the graphics in XML format 👈🏻
- Every element and every attribute in SVG files can be animated 👈🏻
- SVG integrates with other W3C standards such as the DOM and XSL
I knew that every character of the captcha image(SVG image) is going to have a unique fix pattern, then Iwrote a javascript code to download multiple captcha images with all the possible character patterns and saved all the patterns into a key value json format.
If you want to head straight to the code , you can find it here on GitHub.
The demo page looks something like this.
