Of course not. If China could break modern encryption, that would be a state secret of the highest possible order, not something you'd piece together axiomatically on a message board from a policy pronouncement.

If they can frighten people into believing 256 bits isn't enough, interesting parties will self-select, by using stronger ciphers, aiding traffic analysis.

That was mainly my concern when I read the news. Its unlikely they are capable of doing that now, but they are certainly working hard on it, and people moving to 512 bit encryption before then will probably result in years of hard work down the drain. But it is still concerning that they even think that 256 bit encryption is crack-able in the foreseeable future.

It’s not that 256 bit encryption will be crackable soon. It’s that flaws in the implementation of the encryption algorithm will allow access to the partial key.

So 256 can become 128.

>Its unlikely they are capable of doing that now, but they are certainly working hard on it,

What makes you say that, and what new information would indicate when "unlikely" had turned to "likely"?

They probably realized that 256 bit is so ubiquitous already that it would be a major upheaval to all of a sudden regulate it. Seems like the intention could be forward looking to the future.

That's the first thing I thought, the second was "Why does China want to make the rest of the world believe they can crack 256?"

As others have pointed out this isn't practical on current hardware. However with quantum computers I've read that there are already algorithms which would make short work of it. What I'd be curious to know is whether the key length has any bearing on the speed of said algorithms.

My guess would be that key length scales the quantum algorithm time much less than it scales the possibilities. Like, as key length squares, execution time doubles.

I don't know. It's seems crazy that an algorithm wouldn't be affected at all by significant numerical increases.

Possibly yes, although it could also mean they are doing this now for the future. It makes sense because post-quantum symmetric encryption may need higher key lengths, although it is currently still believed that 256 bit keys should provide the equivalent of 128 bit classical keys.

Not nescessarily. But certainly places bounds on the budget to do so.

256 bits is out of bounds for brute forcing for any realistic amount of hardware you throw at it. So either they have attacks on the actual algorithms that drastically cut down the complexity compared to a brute force attack, or this law doesn't do very much (other than perhaps pave the way for other laws).

It's also out of bounds for brute forcing for any realistic amount of Dyson Spheres you throw at it.

For those who don't get the reference:

"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 infeasible until computers are built from something other than matter and occupy something other than space."[0]

[0]https://www.schneier.com/blog/archives/2009/09/the_doghouse_...

Formatting removed some ^ symbols.

It's worth noting that if those Dyson spheres were quantum computers (and we ignored light-speed delays even within single spheres) you'd only need to count up to 2^128, not 2^256 to brute-force a 256-bit key. Still well outside the realm of possibility for anything smaller than a Dyson sphere.

I didn't get the reference, thanks!

I read about the NSA (I believe, or another TLA) having identified some weaknesses in encryption algorithms (RSA I think, though again, memoria fragilis est), that means they could just about break some cyphertexts.

The context was that, although the agency was committed (hmm) to making cybersecurity better for US citizens, and thus helping the cryptography community to improve security, they felt OK exploiting weaknesses, so long as they thought it would be too difficult for others to do so too.

Sorry it's so hand-wavy, I'd love to find the article for my own sake, but busy/hard to google.

you may be thinking of the logjam attack on dhke

What budget? At 256 bits (and even far less) it's not a question of money. It's a question of energy. We don't have enough energy production to even execute a single repeating adding instruction that bit-flips 256 bits of data registers to just count up from 0 to 2^256-1, and even if we did we don't have computer setups capable of ingesting such energy. Never mind the fact that encryption rounds and result analysis increases the energy consumption some hundred orders of magnitude.