CAPTCHA: using hard AI problems for security
Luis von Ahn,Manuel Blum,Nicholas Hopper,John Langford +3 more
- pp 294-311
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TLDR
This work introduces captcha, an automated test that humans can pass, but current computer programs can't pass; any program that has high success over a captcha can be used to solve an unsolved Artificial Intelligence (AI) problem; and provides several novel constructions of captchas, which imply a win-win situation.Abstract:
We introduce captcha, an automated test that humans can pass, but current computer programs can't pass: any program that has high success over a captcha can be used to solve an unsolved Artificial Intelligence (AI) problem. We provide several novel constructions of captchas. Since captchas have many applications in practical security, our approach introduces a new class of hard problems that can be exploited for security purposes. Much like research in cryptography has had a positive impact on algorithms for factoring and discrete log, we hope that the use of hard AI problems for security purposes allows us to advance the field of Artificial Intelligence. We introduce two families of AI problems that can be used to construct captchas and we show that solutions to such problems can be used for steganographic communication. captchas based on these AI problem families, then, imply a win-win situation: either the problems remain unsolved and there is a way to differentiate humans from computers, or the problems are solved and there is a way to communicate covertly on some channels.read more
Citations
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Proceedings ArticleDOI
How Good Are Humans at Solving CAPTCHAs? A Large Scale Evaluation
TL;DR: In this paper, a large scale evaluation of captchas from the human perspective is presented, with the goal of assessing how much friction CAPTCHAs present to the average user.
How good are humans at solving captchas a large scale evaluation
TL;DR: Evidence from a week’s worth of eBay captchas suggests that the solving accuracies found in the study are close to real-world values, and that improving audioCaptchas should become a priority, as nearly 1% of all captchAs are delivered as audio rather than images.
Proceedings ArticleDOI
New client puzzle outsourcing techniques for DoS resistance
TL;DR: In this paper, the authors explore new techniques for the use of cryptographic puzzles as a countermeasure to Denial-of-Service (DoS) attacks and propose simple new techniques that permit the out-sourcing of puzzles; their distribution via a robust external service that they call a bastion.
Proceedings Article
Re: CAPTCHAs: understanding CAPTCHA-solving services in an economic context
TL;DR: This work examines the market-side of this question in depth, analyzing the behavior and dynamics of CAPTCHA-solving service providers, their price performance, and the underlying labor markets driving this economy.
Proceedings ArticleDOI
What's up CAPTCHA?: a CAPTCHA based on image orientation
TL;DR: A new CAPTCHA which is based on identifying an image's upright orientation is presented, which is language-independent, does not require text-entry, and employs another domain forCAPTCHA generation beyond character obfuscation.
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