ScatterType: A Legible but Hard-to-Segment CAPTCHA

The ScatterType CAPTCHA, designed to resist character– segmentation attacks and shown to be highly legible to human readers, is analyzed for vulnerabilities and is offered for experiments in automatic attack. As introduced in [BR05], ‘ScatterType’ challenges are images of machine-print text whose characters are cut into pieces which then drift apart, in an attempt to frustrate segment-then-recognize computer vision attacks. Analysis of experimental human legibility data has shown that better than 95% correct legibility can be achieved through judicious choice of the pseudorandom generating parameters [BMW05]. That analysis is summarized and discussed here as motivation for a discussion of potential vulnerabilities. An invitation to attack ScatterType is offered.

• Type: Conference
• Year: 2005
• Where: ICDAR
• Authors: Henry S. Baird, Michael A. Moll, Sui-Yu Wang
• Keywords: Character– Segmentation Attacks, Correct Legibility, Document Analysis, ICDAR 2005, Pseudorandom Generating Parameters