It'd be nice if GoldMoney sponsored a block-chain currency with units backed by gold. They'd control the issuance (no block solution rewards--only transaction fees for mining) and promise to buy the currency at a certain rate of gold. (The rate would decrease slowly over time--or the chain would need demurrage--in proportion to the gold storage costs.)
If I were to do this, I'd design the GoldCoin
chain with a shared proof-of-work system
(merged mining) from the outset to defend against 51% attacks. The currency would not be decentralised the way Bitcoin is, but if successful, it might rise in value enough to dwarf the underlying asset and become de facto decentralised. The gold backing will have been be just a bootstrapping technique, an advancement
over Bitcoin's 50 BTC block generation reward. To compensate for the cost of mining (low due to shared proof) during the early stage, the gold holder would simply pay miners, perhaps via a mechanism much like block rewards.
The software would recognise some special keys as belonging to the GoldCoin issuer. We'd need an incentive for miners to include messages signed by them, such as new issuance transactions. (GoldCoin units would be created only upon transfer of the corresponding amount of gold-backed currency to the issuer's dedicated account.) I'd write the software so as to regard a block containing an issuer message as "higher" than one without it, thus expressing users' desire to receive the messages. Other official messages might include price quotes, software or protocol upgrades, news, etc.
Exchange between the digital gold currency (DGC)
and the cryptocurrency could be fully automatic. Transfer your DGC to the official account with your address in the memo, and the GoldCoin issuer promises to issue new currency to that address. Send your GoldCoin to a specially formatted address, which encodes your DGC account number, and the issuer promises to deposit DGC at the current official rate. If the GoldCoin issuer and the DGC issuer are one and the same, there is no additional trust issue beyond trusting each currency.
GoldMoney won't do this or allow anyone to do it with their DGCs due to regulatory concerns. Perhaps one of its competitors will. Pecunix? Liberty Reserve? I post this partly in the fear that GoldMoney will patent the system and prevent its implementation for 20 years. Of course, the same system could work with commodities other than gold: silver, cash, baskets of commodities, etc.