Paper tokens: Produce 100 billion authentication tokens (could be passwords, could be private keys of signed certificates), print them on thick paper, fold them up, publicly stir them in giant vats at their central manufacturing location before distributing them to show that no record is being kept of where each token is being geographically routed to, and then have them freely available in giant buckets at any establishment that already does age-checks for any other reason (bars, grocery stores that sell alcohol or tobacco, etc.). The customer does the usual age-verification ritual, then reaches into the bucket and themselves randomly selects any reasonable number of paper tokens to take with them. It should be obvious to all parties that no record is being kept of which human took which token.
Require these tokens to be used for something besides mature-content access. Maybe for filing your taxes, opening bank accounts, voting, or online alcohol / tobacco purchases. This way, people requesting these tokens do not divulge that they are mature-content consumers.
Paper tokens: Produce 100 billion authentication tokens (could be passwords, could be private keys of signed certificates), print them on thick paper, fold them up, publicly stir them in giant vats at their central manufacturing location before distributing them to show that no record is being kept of where each token is being geographically routed to, and then have them freely available in giant buckets at any establishment that already does age-checks for any other reason (bars, grocery stores that sell alcohol or tobacco, etc.). The customer does the usual age-verification ritual, then reaches into the bucket and themselves randomly selects any reasonable number of paper tokens to take with them. It should be obvious to all parties that no record is being kept of which human took which token.
Require these tokens to be used for something besides mature-content access. Maybe for filing your taxes, opening bank accounts, voting, or online alcohol / tobacco purchases. This way, people requesting these tokens do not divulge that they are mature-content consumers.