Alan Boyle has a post on the current state of the art in detecting fauxtography. As the researcher notes, this will always be an arms race. With molecular manufacturing, it's going to become possible to create copies of art that is indistinguishable from the original. I also think that it will mean an end to cash, because it won't be possible to create uncounterfeitable currency.

Actually, we could pretty easily make an "uncounterfietable currency" even now. All you do is implant a chip (preferably a flexible chip!) in each dollar. The chip would be programmed with a private signing key, in such a way that trying to reverse engineer the chip erases the data (this technology already exists, to a certain extent). To verify the dollar, you send it some random data and it signs the random data with the private key. The verifier can then verify the signature with a public key.

Using this, you have to know both the atomic makeup and the electronic state of every atom. I think it will always be possible to prevent that, or at least make it more expensive to counterfiet than the possible returns.

(Remember, there are easy ways to give the currency a use by date - just update the signing certificate just like SSL)

The cost of this "molecular manufacturing" thingy matters. If it costs $120 to counterfeit a $100 bill, nobody will do it.

The chip would be programmed with a private signing key, in such a way that trying to reverse engineer the chip erases the data (this technology already exists, to a certain extent).

So, dismantle the chip, atom by atom, observe and record its configuration, then make exact copies. How would you prevent that?

Carl, it's assumed that the costs of molecular manufacturing, once the technology is mature, are arbitrarily low (basically the cost of the energy required to assemble the atoms in the desired configuration).

We could use coins. They are expensive to duplicate and they last longer than paper money, so are more cost effective for the government to produce. It would be kind of cool; men would go back to carrying coin purses. Maybe men could even start carrying handbags.

Gold,silver,platinum, et c.

So, dismantle the chip, atom by atom, observe and record its configuration, then make exact copies. How would you prevent that?

The easiest way is for the chip to detect the start of the dissassembly and scramble the data. For every what if you provide, I just come back with another what if response. If I can make it cost in the billions to do, then I have eliminated counterfeiting. If I make it cost in the millions to do, I have greatly decreased couterfeiting. Currently, it just doesn't cost much to do...

The key reason to do this is that you can easily change the currency (make a new signing cert) every year or so. That makes it much harder to counterfeit, because it requires a large investment to retrieve data that will only be useful for a short time. Digital security works because of asymetry of effort - signing a document with the private key take little work, signing a document faking a private key takes more time than the universe has left. The same ideas can work in physical security - printing money with the key takes a shorter time than printing money without the key. Then all you have to do is expire/replace the money on a time frame shorter than the difference between the two.

"If it costs $120 to counterfeit a $100 bill, nobody will do it."

Nobody will do it *to* *make* *a* *profit.* But if you want to trash an economy, you might be willing to go to the expense.

"If it costs $120 to counterfeit a $100 bill, nobody will do it."

Nobody will do it *to* *make* *a* *profit.* But if you want to trash an economy, you might be willing to go to the expense.

Not unless you have a spare "economy" handy that is at least a significant fraction the size of the target economy and which can be entirely liquidated to pay for the attack. The U.S., at least, appears quite safe against such a scenario. Andorra or Vanuatu, on the other hand, better look out!

Un-counterfeitable currency assumes, not just molecular manufacturing, but molecular copying. Nothing could be easier to defeat. Ever hear of a guy named Heisenberg?

Quantum cryptography already has tap-evident transmission techniques. The same principles would produce reverse-engineering-evident tokens. Thus, you would have to destroy a $100 token to produce a fake $100 token.

New item, 1132AD.

Alchemists today said that gold as a monetary standard will soon be obsolete, as the "Philosopher's stone" will allow base metals to be turned into the yellow substance. Parchment at 11.

And the SF crowd reports back from the 1930s, with "Venus Equilateral" and the duplicator, and "First Lensman" and the Patrol's problems with creating an unforgeable identification symbol...

Where are the Arisians when you need them?

Has anyone looked into whether molecular manufacturing is going to make it possible to build large numbers of particle accelerators so small (maybe, the size of a cell?), and to hold target nuclei so precisely in the beams, that we could transmute elements efficiently?

If so, it might not be good enough even to use coins made of precious metals. There won't be any precious metals anymore. But then a whole lot of things will change if transmutation becomes feasible.

People don't like to lose money which is one of the advantages of traditional money... you can count it. Encoded money on a plastic card is really hard to count at a glance, you need some kind of reader, a serious inconvenience. Ah, but what if a digital readout was on the card itself?

Otherwise plastic coin purses would be very popular IMHO and superior to credit and debit cards for the same reason cash (by perhaps a slim margin) is.