Dynamic Image CAPTCHA System for Bot Attack Prevention
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Solution Overview
Problem
Current CAPTCHA systems can be circumvented by techniques employing crowdsourcing, where human intelligence is systematically deployed to assist bots in passing security tests, compromising the security of web-based services.
Innovation Solution
The Dynamic Image CAPTCHA system uses dynamic images with unique identifiers and time limitations to prevent abuse, ensuring that images and questions change periodically, making it difficult for bots to exploit human assistance through crowdsourcing platforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional static CAPTCHA images are used, then the system is easy to implement and pass, but it can be circumvented by crowdsourcing techniques
Solution Approach 1:
The patent applies dynamics by transitioning from static CAPTCHA images to dynamic image sequences. Each CAPTCHA challenge presents a series of images that change over time, requiring users to identify objects across multiple frames. This dynamic approach prevents bots from using pre-trained models on static images, as the temporal variation and sequence-dependent patterns cannot be easily captured by conventional computer vision systems, thereby improving security while maintaining reasonable system complexity
Solution Approach 2:
The patent implements periodic action through time-limited image sequences where images are displayed for a predetermined duration and automatically refresh or expire. This periodic presentation creates time pressure that prevents automated systems from systematically analyzing and solving CAPTCHAs, while human users can still complete the task within the time frame, thus enhancing security without significantly increasing system complexity
2Reliability
If time limitations are imposed on CAPTCHA completion, then crowdsourcing abuse is prevented, but user experience may be degraded
Solution Approach 1:
The patent applies partial action by imposing time limitations only on the CAPTCHA verification process itself, while allowing users sufficient time to understand and respond to the challenge. The time limit is set to be restrictive enough to prevent automated crowdsourcing attacks but lenient enough for human users to complete the task, thus preventing abuse while maintaining acceptable user experience
Solution Approach 2:
The system provides immediate feedback when a user successfully completes the CAPTCHA within the time limit, confirming their human status. This feedback mechanism allows the system to adaptively manage time constraints, potentially adjusting difficulty or time limits based on user performance patterns, thereby preventing crowdsourcing abuse while optimizing user experience through responsive interaction
3Measurement precision
If multiple dynamic images with unique identifiers are used, then bot detection accuracy improves, but processing requirements increase
Solution Approach 1:
The patent applies segmentation by dividing the CAPTCHA verification process into discrete image frames, each with unique identifiers. Instead of processing one complex static image, the system processes multiple simpler dynamic frames sequentially. This segmentation improves bot detection accuracy by capturing temporal patterns and motion characteristics, while reducing per-frame processing energy requirements compared to analyzing a single high-complexity image
Solution Approach 2:
The system uses lightweight visual features and simplified object representations in the dynamic images rather than processing full-resolution complex images. By using representative copies or simplified versions of visual data with unique identifiers, the system achieves high bot detection accuracy through pattern recognition across sequences while minimizing server processing energy consumption
Data Source
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AI summary
The invention is related to a "Completely Automated Public Turing test to Tell Computer and Human Apart" (throughout the following abbreviated by "CAPTCHA"), and in particular to a method for providing a CAPTCHA employing dynamic images and a system therefor.