We use a random number generator that has been certified by 3rd party auditors at Gaming Labs International (GLI). You can find our certificate here: https://yotta-assets.s3.amazonaws.com/gli/Yotta+GLI+Certification.pdf and here https://access.gaminglabs.com/Certificate/Index?i=482.

You can also find our prior results here https://www.withyotta.com/transparency to validate randomness.