Breaking the Silk Road's Captcha
This a great writeup and super easy to follow along with. The figures are really nice!One observation: training a neural net to classify segmented characters is probably overkill. The author observed that the font never changed, but never ended up exploiting this fact. After the very effective preprocessing, thresholding, etc the characters are almost identical to the 'average' representations the author generated!I bet it would be enough simply to classify an unknown character by the letter that it shows highest correlation with.