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Comment Re:I can hash fingerprints (Score 2) 242

Why not? I remember seeing an example of how to hash fingerprints something like 20 years ago. It may not work with the current fingerprint checking tools but it went something like this:

1. user (fingerprint owner) Generates a random image the size of the fingerprint image.
2. Add error correcting - e.g. an R-S code on the rows and columns
3. Hash this resulting data
4. XOR the image in 2 with the fingerprint.
5. Send 3 and 4 to the person who wants to verify the users fingerprint later.
(User might want to save a hash of 4 so that they can verify that when presented with this data again they can tell it hasn't been tampered with)

When the time comes to verify the fingerprint:

1. Verifier sends 4 above to the user
2. User XORs their fingerprint with 1
3. Apply error correcting to 2
4. Generate the hash from this data and send to verifier
5. Verifier compares with hash stored. aka password.

The challenges are related to detecting the rotation and position of the fingerprint when you don't save any data about the fingerprint itself. What you need is an algorithm that can consistently align a fingerprint by shifting and rotating a fingerprint when it's presented slightly differently.

There's also the challenge of getting the amount of error correcting correct. Too little and the random image recovery won't work. Too much and you'll start accepting fingerprints that are similar but different or allow brute force to recover the hash.

Comment Re:I can tolerate a really hot hottub (Score 3, Informative) 488

Those cities are currently, probably, about as bad as the Middle East when worst cases are considered and, currently, are not particularly close to "limit of survivability" levels.

Some bits of Northern India are currently amongst the "worst" areas. The ME is geographically close but currently not so bad as they're drier.

But if the ME gets wetter then the problems there could get worse to the point where it's impossible to survive without aircon.

35C wet bulb temperature is about the limit of survivability. You don't die instantly but unless you get somewhere cooler (lower wet bulb temperature, not necessarily absolute temperature) you will die.

Comment Re:The contriversial parts in brief. (Score 4, Insightful) 115

In other words, why track every member of the public to see if any of them view instead of just looking at subscribers to that site?

You've completely missed the point of why they want to do this.

They don't care at all about this data. What they care about is that GCHQ, MI6 etc can continue to capture everything in a dragnet (something that they claim was already allowed but was kept so secret that even most of the people in the organizations that were doing it didn't know it was happening.

They need a way to use that dragnet without admitting to actually capturing everything and possibly decrypting some of it. They'll use the records collected by the ISP to build a case against someone.

Once they get good at bulding cases that judges like they can use those skills to take the data from the ISPs to build a case against anyone they don't like for any reason.

Given the dozens of different domains that data is fetched from for any given page I suspect there's an almost unique fingerprint of connections for many webpages.

If this bill passes you will also no longer be able to trust things like the raspberry pi - in fact, any hardware made or assembled in the UK will be suspect.

Comment Re:It must be a biased study (Score 1) 319

Where did these people work before NASA? They need to be investigated.

It's OK. No need to worry. You can ignore this report. At least one of the authors has already been "investigated" and found to be wanting by the skeptic croud. He is one of the "alarmists" predicting that if the trend to 2007 continued then arctic sea ice could disappear in 2012.

He also, according to the skeptics, cherry-picks:


And, indeed, he's (obviously deliberately) done it again here: only using the data to 2008.

On a less facetious note, this could be good, bad, or make no difference to existing thoughts.

Good - some mechanism not considered is allowing substantial transfer of mass from the oceans to the interior of Antarctica. In the shorter term at least this could make sea level rise much less than currently anticipated over the next few centuries.

Bad - there's a much larger than believed loss of ice-mass from somewhere else and the current estimates of expected sea level rise will turn out to be severe underestimates when, e.g. the Greenland icesheet disintegrates and falls into the ocean.
(The only two mechanisms I can think of to account for the observed sealevel rise and the assumption that Antarctica didn't lose mass are much more loss from Greenland or thermal expansion. Excess energy going into heating of the oceans could account for the "pause" too)

Indifferent - there's a short-term mechanism that can temporarily move ice mass into interior Antarctica. This can occur over a decade or two before reestablishing longer term trends. This will add noise to the system and make it harder to estimate long term trends from shorter term data but doesn't significantly alter trends from longer terms.

Comment Re:Who took the decision to undertake the work? (Score 2) 169

From the press release from the HSE he wasn't working on live equipment.

He was given a work permit by the site operator to route some power but the route was through other equipment that had exposed live connections. The electrician made inadventent contact (with his forehead) with one of these exposed live connections.

Worse, the site operator was aware of this risk, and was aware that whether these exposed terminals were live or not was not under their control but they had a disregard for the risks when issuing the work permit. They got fined £100K for this. (The other company got fined nearly three times as much - presumably for leaving exposed live connections that could accidentally be touched and not marking the area as restricted/dangerous.)

Basically this seems to have been a mega screwup between the management of two companies working on the same site who appear to have had no way to safely coordinate work where the areas of responsibility overlapped.

Comment Re:The fine won't hurt the DC owners. (Score 1) 169

Someone made the call to have live circuits worked on, despite this being illegal.

In the UK - where this happened - it's not illegal to work on live circuits. The HSE has this in the FAQ:

When is it safe to work on live electrical equipment?

It is never absolutely safe to work on live electrical equipment. There are few circumstances where it is necessary to work live, and this must only be done after it has been determined that it is unreasonable for the work to be done dead. Even if working live can be justified, many precautions are needed to make sure that the risk is reduced 'so far as is reasonably practicable'. See: Electricity at work: Safe working practices for more details.

Comment Re:I just can't really rejoice (Score 2) 59

because frankly, what private citizen will need a lot of international calls

This has come about, partly, because some people were incurring huge roaming charges without even going abroad.

For example, in some parts of the south coast of England it's possible (sometimes even likely) that you'll get a much better mobile signal from France than from the UK.

People had to have two sims - and remember to put the French one in when at home and the English one in when they went to town.

Then, a mobile operator would put up a new mast in the UK - some people who used to get a French signal now got that new mast instead. And so now they were using their French sim which used to avoid roaming charges and got roaming charges.

I presume similar happens (probably even more commonly) on any of the other international borders in Europe but it was the problems for people on the south coast that I've seen reported on in the past.

I also suspect that the fact that if you are "in the know" you can roam cheaply - just buy a cheap sim in each country you visit - also influenced the lawmakers. And the fact that consumers were able to run up HUGE bills without realizing, tens of thousands of pounds in some cases. In the EU, in business to consumer contracts, it's generally supposed that the business will do everything in their power to ensure that the consumer gets what they (reasonably) expect and "catching out" consumers is not looked upon favourably even if a contract apparently allows it.

Comment Re:Oh... (Score 1) 129

The act of accellerating should be what opens the gap behind you for the car in the next lane to merge into.

Yes but it needs to happen so that by the time you've actually reached the pinch point you're doing the correct speed.

Two lanes of traffic doing 30mph. They merge as they accelerate to 60 which opens up the gap. If they don't start accelerating before they merge then they enter the pinch at 30 - which means that the two lines of traffic behind are doing 15 etc.

(Ignoring increasing gap size between cars as the speed increases so it's not quite as simple as divide the speed by two but it's a good rule of thumb provided the traffic volume isn't too high.)

Comment Re:Oh... (Score 1) 129

No. Every problem in NP cannot be converted to every other problem. (unless P=NP)

There are 'hardest' problems in NP that every problem in NP can be converted into.

But there is an infinite number of 'difficulty' levels and problems cannot be converted to an easier problem.

(you do mention NP complete in your second sentence so I suspect you 'miswrote' rather than misunderstand.)

Comment Re:Oh... (Score 1) 129

I think it's because if two lanes go down to one and the one lane has a speed of 60 then the only two ways to get maximum flow is to either:

a. double the gap between the cars prior to merging so that the merge can happen at 60.

b. merge ahead of the single lane so that the merging speed is around 30 but there's time to accelerate again before the single lane.

a. feels smoothest and can be done with minimal speed changes but, once it goes wrong causes a merge speed of zero at the pinch point until it sorts itself out again.

b. works provided there aren't too many arseholes who zoom past the point the lanes are merging. Often this can be controlled by drivers merging into one lane over a much longer distance than necessary.

It's frustrating when you get to the pinch point at a low speed and then accelerate because that pretty much proves it lack of planning and anticipation by other drivers has held you up. (unless you're that arsehole who braked hard at the last minute to merge and then had to accelerate again forcing others to do the same)

Comment Re:I've been waiting for this! (Score 1) 257

I don't know what you mean by "backtracking" but you cannot reproduce the results of QM using a computer without communication between them.

Setup 1000000 experiments where a "particle" is in state |1> Orthogonal states are |+> or |->

Calculate hidden variables for the results of measuring state |a> |1> and |b> where |a> is slightly perturbed towards |+> and |b> towards |-> by angle theta.

"Copy" the states onto another computer so that they are "entangled" (strictly this would mean that one computer will have |1> or |0> randomly and the other will have |0> or |1> respectively but it doesn't actually matter for showing Bell's inequality.)

Send the "entangled" states to two parties, Alice and Bob

Each of those parties decides to measure |a> |1> or |b> randomly.

Where Alice and Bob both measured the same state they got the same result (due to your precalculated hidden variables)

Where one measured |1> and the other measured |a> the number of anti-coincidences should be 1-cos^2(theta/2).

Ditto for |1> and |b>

So far, so good.

But now consider the case where one measured |a> and the other measured |b>. The upper bound on the number of anti-coincidences is 2-2cos^2(theta/2). However QM requires 1-cos^2(theta) which is roughly twice as big for small theta.

Comment Re:I've been waiting for this! (Score 1) 257

Part of the reason you've never heard a convincing argument is that there isn't a classical way of describing this.

Imagine Alice has some "magic" ink.

She can write in blue, yellow, magenta or green or combinations of them.

However, these inks are "magic" in that blue and yellow exactly cancel each other out. If you mix the blue and yellow inks together you're left with an ink in which ever colour there was the most of. It's not paler. If you mix in exactly the same quantities then the ink disappears completely.

Ditto magenta and green.

Alice mixes an ink colour together from these four inks. As some inks cancel each other out we can define the final colour by one number being the angle the final colour makes on a circle with magenta at the top, green at the bottom, blue on the left and yellow on the right.

These magic inks have another peculiar property. You can only ask "yes/no" questions to tell what colour they are and the act of asking the question forces the ink to the appropriate colour.

So, if you have a yellow ink and ask "is it yellow" then the answer is yes - with 100% probability.

If you ask "is it blue" then the answer is no - with 100% probability.

Things get weirder when you ask "is it green". If the answer is yes then the ink is green - so it changes from yellow.

Remember that these magic inks disappear if you mix eactly the same quantity of magenta and green. So if you have an ink it must be either magenta or green. Otherwise the ink would have vanished completely and there wouldn't be any ink to be asking questions of.

If the answer to "is it green" is no then that means the ink must be magenta instead - so a no answer to "is it green" turns the ink magenta.

Because a yellow ink is neither green nor magenta in reality but the "is it green" question requires an answer, the answer will be randomly yes or no with 50-50 probability.

N.B. Because the ink actually changes colour after the first "is it green" question repeatedly asking the same question will get the same answer.

But you don't have to limit yourself to these two axes - instead we can ask "is it a 50/50 magenta/yellow mix. If the answer is yes then it really is a 50/50 magenta yellow mix. If the answer is no then it's a 50/50 blue/green mix instead.

If the ink started out as yellow (we asked "is it yellow" and the answer was yes) and then we ask "is it a 50/50 magenta/yellow mix" then we're more likely to get a yes than a no answer.

If we make the measurement we find that the probabilty of getting a yes answer is the square of the cosine of half the angle between the initial colour and the question we ask.

Now to Alice, Bob and Carol's problem. Does the ink "know" the answer to any question you can ask of it.

Let's say that Alice used yellow ink.

If Bob and Carol both do the "is it yellow" test then they both get a yes answer.

But instead, lets assume that they both do the "is it green" test. We've already established that the answer to this is yes or no with 50/50 probability. So we can get yes/yes, yes/no, no/yes and no/no as the four possible combinations of answer. But... where it gets weird is where the ink on the two letters is entangled. Bob and Carol both get the same answer - i.e. the only answers are "yes, yes" and "no, no"

This is what entangled means - if you make the same measurement you get the same answer (where same actually means opposite in most experiments)

(in practice you have to repeat the experiment over and over again to establish that B&C always get the same answer to whatever question they ask. To avoid problems where the ink "knows" what test will be done in advance when Alice mixed it they randomly decide what test to do at the last possible moment and then compare answers and only use the cases where they randomly chose the same test to do)

Lets assume that Alice writes in yellow ink that is entangled between Bob and Carol's letters.

If you actually work out the maths for different angles between the sender and the receivers you discover that there's a difference in the probability of getting certain results depending on whether there is a hidden variable.

If Bob asks "is it yellow" and Carol asks "is it yellow with 1% green[1]" then they get the same answer in all but 8 times out of 100000 when Carol gets a no answer. If there's a hidden variable then it will have a no recorded 8 times out of 100000 that Alice mixes the ink for this test.

If Bob asks "is it yellow with 1%magenta" and Carol asks "is it yellow" then they also get the same answer in all but 8 times out of 100000. Ditto - a hidden variable encodes a no 8 times out of 100000 for this test.

If Bob asks "is it yellow with 1%magenta" and Carol asks "is it yellow with 1% green" then assuming that the ink knows what the "right answer" for any question is then the MAXIMUM number of times B&C will get different answers is 16 (8+8) per 100000 tests.

However. if we start with "yellow with 1% magenta" and then ask "is it yellow with 1% green" we get a no answer 30 times out of 100000.

When Alice, Bob and Carol do this test they find that the times that Bob and Carol get different answers when they both measure "off yellow" is around 30 times per 100000. This shows that the ink cannot "know" the right answer to give to any question in advance.

[1] When I did these calculations just now I assumed that yellow with 1% magenta was 1 degree from yellow.

Comment Re:Distance? (Score 1) 257

Entanglement IS communication, in the proper sense of the word. You cannot use it to send a message, but entanglement without hidden variables implies that information is exchanged between particles.

Only if you assume that there are two particles while they're entangled. If there's only one particle then there is no communication between them. On measurement it changes from one to two particles.

One photon can go down both arms of an interferometer - one particle in two different places but the act of measuring it in one arm causes the part in the other arm to vanish.

An entangled pair of photons can go down both arms - detecting it in one arm causes the part in the other arm to appear.

Every little picofarad has a nanohenry all its own. -- Don Vonada