"And here is our solid matter encryptor."

The bank tour is almost over. Vaughn, an electronics technician posing as himself but with several orders of magnitude more means than he truly has, has been trying to conceal his anticipation. He is almost certain that his cover is leaking, that the polite businesswoman who has shown him the bank's facilities can see directly through the figurative mask, that this is all stalling for time until the police arrive. He feels a drop of sweat roll down one knuckle. He's carrying a heavy briefcase.

"This, ah solid matter encryption... is rather new to me," Vaughn lies.

It's very new technology, extremely fancy. It's been used for military purposes, but only a few of the wealthiest banks have access to the technology and provide it to customers. The bank operative, Platt, beams at the question, and launches into the pitch.

"Solid matter encryption is an optional service you may use as part of purchasing a safe deposit box with us. It provides an extra layer of physical security over the top of gates, doors and locks and keys. If you have a moment, I'd be delighted to provide you with a full demonstration."

Vaughn agrees.

"When a customer comes through to access a safe deposit box, we of course provide them with complete privacy. Let's imagine you're a customer and this... hah, fake example passport was something you wanted to deposit. Ordinarily, the system works as follows. I unlock the numbered metal box which you have access to. I provide you with the unlocked box, and give you privacy. You open the box, put your passport in the box, close it again, and give it back to me. I lock the box and return it to the rack of lock boxes."

"I'm familiar with that procedure," Vaughn says.

"With solid matter encryption, you don't put your passport in the box. Instead you put it into the hopper of our solid matter encryptor, here. This is large enough to accommodate a short stack of A4 paper. You enter a encryption key... or, if you wish, we can generate a cryptographically secure key for you, or we can scan a printed code, if your key is too long to type out yourself. You seal the hopper, and the machine encrypts all of the matter in place..."

There is a high-pitched whine, and a blast of violet light, and some quantum mechanical magic happens. Platt opens the hopper again, revealing an ugly black block of dense nonsense. The block appears complex, as if made from densely packed particles or fractals, and from different angles it displays weird colours, but predominantly it is a simple matte black lump. Platt takes the lump out — it seems to have the density of some heavy stone. It has exactly the dimensions of the smallest standard safe deposit box. She slides the block into the box and locks it.

"Now the matter is encrypted. This is an advanced, proprietary state of matter called CryptoMatter. Now, even if someone were to steal your deposit box, and successfully pick the lock, they'd still have nothing. The only way to recover your original passport would be to know your key. Which only you know. Additionally, they would need access to a matter encryptor. These things are very expensive, very highly regulated, and require immense quantities of power to operate. We have twin dedicated high-voltage lines. Here, see? And of course you noticed the high energy warning signs. There is a premium for this service, because of the amount of energy drawn in each encryption or decryption operation. If you decide to open an account with us, you'll be allowed to use the machine only twice on each visit to your safe deposit box."

Vaughn loves the machine. It's an impressive device, with some impressive engineering going into it. "And to restore my documents?"

Platt unlocks the box again. "We use the same encryption key, like so." She decrypts the passport, and hands it to Vaughn for inspection. There is a faint whiff of ozone, but from a brief flip through its pages, it appears to be precisely the same document.

"The CryptoMatter was a lot heavier than this," Vaughn observes. "Where'd the extra m— excuse me, weight come from?"

Platt shakes her head. "We can set up a meeting with our engineer if you wish. We have some leaflets... but the specific technical details of the encryptor are highly confidential for security reasons, I'm sorry."

"No, that's fine, thank you." Vaughn flipped through one of those leaflets in the waiting room. They're written for a very simple audience.

"It's a different phase of matter entirely," Platt says. "It's not a conventional solid. It doesn't have atoms and molecules. It's something else again. It's also almost indestructible."

"It had better be," Vaughn says. "A slight modification to the brick would constitute data corruption, and the original matter couldn't be recovered. Ms. Platt, I'm sold. I would be delighted to make use of your bank's services. I'd like to make use of an encrypted safe deposit box right away."

Platt beams again.

There follows a trip to an office, and the better part of an hour of paperwork.

Finally, Vaughn has his chance. He's alone with an unlocked safe deposit box and the unattended cryptomatter machine.

He doesn't bother to load anything into the hopper. He pulls up an extremely complex code on his phone and presents it to the machine's reader. It whines into life, drawing down an unusually large amount of power.

"It's not an encryptor," he says. "And proprietary CryptoMatter is an extremely dumb first pass at the technology. It's just an encoder. It just permutes the quantum information in the hopper space. In a totally predictable way. It's going to be a real problem if this ever gets popular..."

Now he has a slab of CryptoMatter. He enters a different code for the decryption, or rather decoding, step. Not the same code as before. And the CryptoMatter doesn't decode to a chunk of fresh hopper air. It decodes to a solid slab of platinum.

"That's the stuff," Vaughn says. He goes to lift the platinum out.

He can't.

It's too heavy. He can't even get his fingers around it. The slab won't budge a millimetre. It must weigh a tonne. Or rather, more than fifty kilograms. Even if he can lift it, how is he going to get it out of here without looking suspicious?

"Ah."

He's used up his two uses of the machine, so there's no way to turn it back into lightweight cryptomatter.

He thinks for a while.

He goes to the door. "Ms. Platt?"

She is waiting patiently. "Can I help?"

"Yes. I... seem to have... hit a technical problem while trying to encrypt my slab of platinum. And I've used up both my uses of the machine. Could you help me?"

Platt uses her discretionary authority to give him a third attempt. He puts the CryptoMatter in the safe deposit box, thanks Platt, and leaves.

And spends a long time trying to think of another way to do this.

Next: Urbane In Urbana