Dynamic Browser Challenges for Stateless Replay-Resistant Verification
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Solution Overview
Problem
CAPTCHA and other obtrusive client verification methods require human interaction and are susceptible to replay attacks, allowing bots to circumvent validation by sharing previously solved problems.
Innovation Solution
Implement a distributed, stateless, and dynamic browser challenge system where each client request generates a unique problem and answer, encrypted and verified across different nodes of a distributed platform without storing the answer, preventing reuse and replay attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a finite set of problems is used for browser challenges, then the verification system is simpler to implement, but the system becomes vulnerable to replay attacks
Solution Approach 1:
The patent implements dynamic challenge generation where the verification system creates new, unique problems on-demand rather than using a static finite set. Each challenge is generated with a random seed and encrypted answer, ensuring that challenges cannot be replayed. This dynamic approach resolves the contradiction by making the system adaptable to security requirements while maintaining operational simplicity through stateless verification.
2Ease of operation
If problems and answers are stored centrally, then verification can be performed, but the system becomes vulnerable to botnet distribution of answers
Solution Approach 1:
The patent extracts the answer from the problem statement by encrypting it separately and providing it to the client in an unreadable format. The encrypted answer is embedded in the challenge response, and the verification system decrypts it locally without needing to store or retrieve answers from a central database. This extraction approach prevents botnets from distributing answers since they cannot decrypt the encrypted values without the verification system's private key.
Solution Approach 2:
The patent introduces encryption as an intermediary layer between the problem and its answer. The encrypted answer acts as a mediator that can be transmitted safely through the network without exposing the actual solution. This intermediary mechanism allows the system to maintain verification capability while protecting against answer distribution by botnets, as the intermediary (encryption) prevents unauthorized access to the actual answer.
3Reliability
If traditional CAPTCHA is used, then bot verification is achieved, but user experience deteriorates due to human interaction requirements
Solution Approach 1:
The patent implements self-service verification where the client's browser automatically solves the mathematical challenge using embedded JavaScript code. Instead of presenting a CAPTCHA requiring human interaction, the system provides a challenge that the browser executes autonomously, generating the solution and returning it for verification. This self-service approach maintains bot detection accuracy while eliminating the need for human interaction, thereby preserving user experience.
Data Source
AI summary
Provided is an unobtrusive client verification system with one verification devices having processors that are configured to receive a first request from an unverified client device, generate a random number in response to receiving the first request from the unverified client device, define a set of expressions as a browser challenge problem that evaluates to an answer specified by the random number, encrypt the answer within an answer token, provide the browser challenge problem with the answer token to the unverified client device, receive a second request with a solution to the browser challenge problem and the answer token from the unverified client device, and verify the unverified client device in response to the solution matching the answer that is decrypted from the answer token provided with the second request.