Crowdsourced Distributed Domain Validation

Domain validation is the primary method used by Certificate Authorities for affirming administrative control over a domain for issuing TLS certificates. Prior work has repeatedly shown its vulnerability to hijacking, prompting the use of multiple vantage points for validation. However, the use of static vantage points, as in Let's Encrypt's MultiVA system, is still subject to targeted attacks. Validators should therefore be both distributed and selected in an unpredictable fashion, which is expensive to achieve with dedicated infrastructure.