the future looks grimm 

FROM: http://www.bitcoinnotbombs.com/bitcoin-vs-the-nsas-quantum-computer/

Posted on January 4, 2014 by Chris — 12 Comments ↓
Yesterday we learned from new Snowden leaks that the NSA is working to build a quantum computer. The Washington Post broke the story with the rather sensationalist headline, NSA seeks to build quantum computer that could crack most types of encryption.

Naturally, this raised much concern among the new Bitcoiners on Reddit and Facebook. The reality, however, is there wasn’t much disclosed that people didn’t already know or expect. We’ve known that the NSA has openly sponsored quantum computing projects in the past. The fact that it has an in-house project called Penetrating Hard Targets is new, but not really unexpected. We learned this project has a $79.7 million budget, but quite frankly that isn’t that much. And as The Post notes, the documents don’t reveal how far along they are in their research and “It seems improbable that the NSA could be that far ahead of the open world without anybody knowing it.”

Nevertheless, this seems like a good time to discuss the implications of quantum computing with respect to the future of Bitcoin.

Let’s start with a little primer for those who are unfamiliar with quantum computing. Today’s computers encode information into bits — binary digits, either “0″ or “1″. These bits are usually stored on your computer’s hard disk by changing the polarity of magnetization on a tiny section of a magnetic disk, or stored in RAM or flash memory represented by two different levels of charge in a capacitor. Strings of bits can be combined to produce data that is readable by humans. For example, 01000001 represents the letter A in the extended ASCII table. Any calculations that need to be performed with the bits are done one at a time.

PhotonQuantum computers, on the other hand, use the various states of quantum particles to represent quantum bits (qubits). For example, a photon spinning vertically could represent a 1, while a photon spinning horizontally could represent a 0. But photos can also exist in a rather weird state called superposition. That is, while they can spin vertically, horizontally, and diagonally, they can also spin in all those directions at the same time. Don’t ask me how that’s possible, it’s the bizarro world of quantum mechanics.

What this means for practical purposes is while a traditional computer can perform only one calculation at a time, a quantum computer could theoretically perform millions of calculations all at once, improving computing performance by leaps and bounds.

Now when journalists write things like, “In room-size metal boxes ­secure against electromagnetic leaks, the National Security Agency is racing to build a computer that could break nearly every kind of encryption used to protect banking, medical, business and government records around the world”, it naturally makes people think it’s the end of cryptography as we know it. But that isn’t the case.

Let’s consider the type attack most people think of when hear of quantum computers―a brute force attack. This is where you just keep checking different keys until you eventually find the right one. Given enough time, you could brute force any encryption key. The problem is it would take billions or trillions of years for a modern computer to brute force a long encryption key. But surely quantum computers could do this right? This is from Bruce Schneier’s 1996 book, Applied Cryptography:

One of the consequences of the second law of thermodynamics is that a certain amount of energy is necessary to represent information. To record a single bit by changing the state of a system requires an amount of energy no less than kT, where T is the absolute temperature of the system and k is the Boltzman constant. (Stick with me; the physics lesson is almost over.)

Given that k = 1.38×10-16 erg/°Kelvin, and that the ambient temperature of the universe is 3.2°Kelvin, an ideal computer running at 3.2°K would consume 4.4×10-16 ergs every time it set or cleared a bit. To run a computer any colder than the cosmic background radiation would require extra energy to run a heat pump.

Now, the annual energy output of our sun is about 1.21×1041 ergs. This is enough to power about 2.7×1056 single bit changes on our ideal computer; enough state changes to put a 187-bit counter through all its values. If we built a Dyson sphere around the sun and captured all its energy for 32 years, without any loss, we could power a computer to count up to 2192. Of course, it wouldn’t have the energy left over to perform any useful calculations with this counter.

But that’s just one star, and a measly one at that. A typical supernova releases something like 1051 ergs. (About a hundred times as much energy would be released in the form of neutrinos, but let them go for now.) If all of this energy could be channeled into a single orgy of computation, a 219-bit counter could be cycled through all of its states.

These numbers have nothing to do with the technology of the devices; they are the maximums that thermodynamics will allow. And they strongly imply that brute-force attacks against 256-bit keys will be unfeasible until computers are built from something other than matter and occupy something other than space.

READ FULL ARTICLE WITH GRAPHS: http://www.bitcoinnotbombs.com/bitcoin-vs-the-nsas-quantum-computer/

Reddit comments: http://www.reddit.com/r/crypto/comments/1ufyvx/bitcoin_vs_the_nsas_quantum_computer/


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