Nearly all blockchains in existence use digital signature schemes for unlocking funds for expenditure, even though this primitive is overkill for that purpose. A commitment scheme suffices, as long as the opening protocol binds to the transaction. Moreover, and perhaps surprisingly, this minimally sufficient primitive can be compatible with an architecture for anonymous payments -- and, incidentally, post-quantum security.

This signature-free strategy does not require public key cryptography except optionally and in the form of an encryption scheme for recipients wanting to receive notifications of incoming payments on-chain. Recipients comfortable with off-chain notifications benefit from the smallest possible transactions and thus transaction fees. This talk covers the life cycle and technical features of transactions in this paradigm, as featured by Neptune Cash.