Lots is possible with fancier crypto. BLS signatures allow non-interactive aggregation, making storage size truly independent of historical transactions, but re

Lots is possible with fancier crypto. BLS signatures allow non-interactive aggregation, making storage size truly independent of historical transactions, but require faith in less well researched pairing-based crypto. RSA accumulators are discussed in another comment. Right now, Grin's design is conservative, relying on the same security assumptions as Bitcoin. The one crucial difference is that money supply is fully verifiable in Bitcoin, while Grin allows undetected inflation if the ECDLP (Elliptic Curve Discrete Log Problem) gets broken.