Comments on: Breaking Rapidshare's Annoying Captcha the Easy Way http://www.algorithm.co.il/blogs/security/breaking-rapidshares-annoying-captcha-the-easy-way/ Algorithms, for the heck of it Tue, 21 Jun 2011 21:07:08 +0000 hourly 1 http://wordpress.org/?v=3.1.3 By: Yoni http://www.algorithm.co.il/blogs/security/breaking-rapidshares-annoying-captcha-the-easy-way/#comment-127 Yoni Fri, 02 May 2008 11:15:58 +0000 http://www.algorithm.co.il/blogs/index.php/misc/breaking-rapidshares-annoying-captcha-the-easy-way/#comment-127 Does this mean one can write a bot that tries all 6choose4 combinations for a single captcha? 1. Interpret all 6 characters with certainty by using a pretty good OCR algorithm. 2. Try all 15 possibilities, simulating a "back button press" after each one. Alternatively: 1. Interpret all 6 characters with certainty by using a pretty good OCR algorithm. 2. Try a random possibility. 3. Repeat ~15 times until success. If either is possible, this extra kitten layer does not offer that much more security... Does this mean one can write a bot that tries all 6choose4 combinations for a single captcha?

1. Interpret all 6 characters with certainty by using a pretty good OCR algorithm.
2. Try all 15 possibilities, simulating a “back button press” after each one.

Alternatively:

1. Interpret all 6 characters with certainty by using a pretty good OCR algorithm.
2. Try a random possibility.
3. Repeat ~15 times until success.

If either is possible, this extra kitten layer does not offer that much more security…

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