Important: Potential Binance Delisting

Yesterday @daira had another idea, which is that instead of introducing a new receiver type to unified addresses, another way to achieve the same goal would be to change the HRP for Revision 1 unified addresses (which define MUST-understand metadata.) I think that this is a good change to make in any case, because it fixes the “legacy wallet” hole in MUST-understand metadata, where a currently-existing wallet could ignore such metadata items.

With that change in place, it then becomes possible to include a source-restriction MUST-understand metadata item, which could be used for the “transparent source only” use case but could also define restrictions like “the transaction must be fully shielded” and/or “the transaction must be fully shielded with no pool crossing”. This generalizes the proposal in a really nice way; it both serves Binance’s use case and it also allows users to request stronger privacy for the transactions that they receive.