> "guaranteed expiration" You could make the database so noisy that there's a proof-of-storage cost on anything over a day old. No guarantee, but something.

> "guaranteed expiration" You could make the database so noisy that there's a proof-of-storage cost on anything over a day old. No guarantee, but something. Adversaries would want to store only those messages of interest, but that would require breaking the oblivious transfer system.