Public HYDD
An unmodified Pons ERC-20. No transfer hooks, no blacklist, nothing a token scanner would flag.
Shielding
Shielding transfers HYDD into the vault and credits shares. Shares are tracked per address in sharesOf; the vault never needs to know which addresses are stealth.
Accounting
The vault tracks totalBacking and totalShares. Every path that moves tokens updates both and emits VaultUpdated, so anyone can audit them.