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Theme fund: NGI0 Entrust
Start: 2022-10
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Privacy-friendly Proof of Work (PoW) based CAPTCHA system

Existing CAPTCHA systems expect visitors to identify objects to prevent spam, which makes the web inaccessible to persons with cognitive, auditory, and visual special needs. They log Internet Protocol (IP) addresses and use tracking technologies, like cookies, to track and profile their users across the internet. IP logging and cookie-based tracking are privacy-invasive, inaccurate, and impossible to use with anonymizing technologies like Tor and VPNs. Censors can abuse the opaque nature of these systems to prevent certain groups from accessing certain types of information. Independent testing for bias is not possible since the documentation doesn't exist for their methods and algorithms.

mCaptcha is an attempt at creating a self-hosted alternative to reCAPTCHA and hCaptcha with a focus on privacy, transparency, user experience, and accessibility. mCaptcha’s Proof of Work (PoW) mechanism uses strong cryptographic principles that guarantee idempotency and transparency. mCaptcha doesn’t log IP addresses and doesn’t require tracking user activity across the internet. Censors can’t use mCaptcha to deny access to information without detection. Also, the PoW mechanism requires minimal user interaction to solve the CAPTCHA, which will significantly improve the accessibility of the web.

Logo NLnet: abstract logo of four people seen from above Logo NGI Zero: letterlogo shaped like a tag

This project was funded through the NGI0 Entrust Fund, a fund established by NLnet with financial support from the European Commission's Next Generation Internet programme, under the aegis of DG Communications Networks, Content and Technology under grant agreement No 101069594.