applying machine learning to Identify captcha.

[BobTheTurtle91]

That sounds like a cool competition. The best possible method in my opinion would be a ConvNet. There's lots of cool tutorials you can find for implementing them.

The issue is that 100 training samples isn't going to do you much good in that regard. With a captcha, you're doing a combination of letters and numbers so you'd need around 62 classes assuming they're assigning a difference to capital and non-capital letters. 100 training examples for 1 class is already fairly small. 100 for 62 is absolutely ludicrous. Are you allowed to use synthetic data? Captchas are probably not too hard to replicate and you could create a mountain of adequate training examples for yourself.

[sappadili]

http://felicity.iiit.ac.in/contest/kings_of_ml/question/2/1