Posts by Vic 5860 publicly visible posts • joined 7 Dec 2007
I still don't follow how a time difference between successive "now" instants on the same system could ever be negative if it's measuring UTC.
Go's Now() function is defined as returning "the current local time", rather than UTC. This would appear to be a blunder.
Vic.
How did the electricity co turn off your supply when you didn't pay your bill in the ancient times of spinning-metal-wheel meters, then? Hint: they didn't send an engineer out to your home.
Well, I've only been disconnected once in my life - but yes, they did send a bloke out.
Vic.
the whole story appears to be bullshit
*Mostly* bullshit.
These things do seem to be monumentally insecure, so breaking into the meter is probably quite easy. But why the original researcher seems to think that means unfettered access to everything the meter does eludes me, as does why even that access might meant you could make it explode...
He seems to have demonstrated some crap security, and then turned the hype meter up to 11 in a desperate attempt to get people to take this seriously - thereby doing the exact opposite.
Vic.
I haven't a clue what your first paragraph means
The analogue signal representing the waveform you're listening to can take any value between two limits. So you can take any two arbitrarily close values you've already got, and you can put another one inbetween. This is a continuous range.
If you digitise that signal, you can now only represent certain fixed values - for an n-bit word, you only have 2n possible numbers, so that is how many values you can represent. There will be times when the value you wanted to represent is slightly different from the value you actually can represent; you can have an error of up to half the step size between two possible values[1]. This is known as quantisation noise, because it manifests itself as noise on the signal, and is solely down to that signal now being quantised (i.e. discrete), rather than continuous. But half the step size is a very small amount of noise[2].
The advantage of going digital early on is that you are incredibly unlikely to have those numbers changed by noise in the system[3]. But were you to remain in the analogue domain, noise will be added at every step[4]. The upshot of all this is that, although digitisation will necessarily add some noise, it's insignificant alongside the noise you'll get from an analogue system. That's why digital signals in real-world situations give you better fidelity.
Vic.
[1] I'm assuming a simple linear conversion; it's a little more complex to calculate the distortion in a non-linear conversion, but we don't do that in CD players, so I don't care.
[2] And that is the peak error; we can expect a Gaussian distribution of real error
[3] A digital signal can take one of two possible states, some distance apart. If you add noise to that signal, it's trivial to work out the desired state of the signal right up to the point where the noise entirely engulfs the signal. So with that (largely irrelevant) exception, a digital signal is not subject to degradation by noise.
[4] Even if we were to ignore induced noise - which is likely the most significant in an analogue system - there are other noise sources, such as Johnson noise, which cannot be avoided.
Dynamic range...Is that the one where they compress it to make songs sound LOUDER? Utterly un-listenable to me.
Dynamic range is the difference between the very quiet bits and the very loud bits. THe more range you've got, the greater the difference.
Compression reduces dynamic range; everything comes out at a fairly similar volume, whether it's supposed to be loud or quiet. It generally destroys music, but can be quite useful in certain niches[1].
Vic.
[1] Usually communications in a noisy environment - so ham radio operators often use a compressor to make themselves more intelligible at the other end. And so do radio DJs, despite that outcome being unobtainable. Proper radio is, of course, uncompressed.
There's a reason why CD took off as quickly as it did
Because you could actually get the start of the track when pissed at a party?
some inferior digital technologies such as MiniDisc and DCC
MiniDisc *could* have been good - the format was very convenient, and the later versions of ATRAC were reasonable on the quality front (but let's not talk about ATRAC1). But Sony bollocksed it up because they wanted to own the format, and make sure no-one was copying their valuable and sacred recordings, so they did their damndest to keep everyone else out of the market.
DCC? I actually have no idea what happened to it. I saw a few adverts early on - then nothing...
Disclosure: I used to work for Sony. At the time MiniDisc was a thing. No, they wouldn't listen to me about opening up the format - you'd think I was recommending barbecuing their grandmothers from the reaction I got...
Vic.
Sometimes that difference can be due to the remastering inflicted on the CD, rather than the difference between formats.
*Always*.
The quantisation noise inherent in the digitisation needed for a CD is orders of magnitude less than the distortion inherent in the analogue stages you need to run vinyl - and that's if we assume a perfect turntable with a perfect pickup[1].
But many CDs were "remastered", which usually meant finding the deafest YTS muppet you could, and getting him to turn all the knobs to 11. And it doesn't matter how faithfully you reproduce that, it will always sound shite.
So if you're one of those people who thinks vinyl sounds better than CD, at least one of the following is true[2] :-
CD *is* more faithful than vinyl. Fidelity is not always what sells.
Vic.
[1] Neither of these can exist, of course.
[2] There is theoretically a third option: you might have a recording with extremely high dynamic range. CDs have a limit, whereas vinyl is actually unlimited - but you're going to lose that range into the noise floor if you actually tried it.
[3] This is more common than you might think - particularly amongst those of us who grew up with vinyl.
Before you get going on this, you might want to read up on the Dunning–Kruger effect.
No they don't
Yes we do.
you can't use pure oxygen underwater due to oxygen toxicity.
You can use pure oxygen underwater despite oxygen toxicity. And we do.
Even enriched oxygen products limit the depth you can dive
Indeed they do. But high-O2 mixes - up to 100% for some people - reduce the time required to decompress from dives. And that is why we use them.
The only time you have high purity oxygen in diving is for post-dive medical treatment for decompression sickness (which wouldn't be frequent) or submersible which is mixing its own gas ratios (once again, not common).
Nonsense on both counts. High-O2 mixes are useful as decompression gases, and there is a whole community of us that carry 100% O2 for continuously mixing our breathing gas underwater. Just because you don't know about something doesn't mean it doesn't exist...
Medical oxygen is usually a minimum of 90% and a maximum of 96% pure oxygen.
Diving Oxygen is better than 99.5% pure, and usually better than 99.9% pure.
Vic.
Which is why you generally use a maximum of 70% oxygen for bottled breathing gas
Speak for yourself. Divers frequently use between 80% and 100%[1] O2.
in 100% oxygen almost everything burns rather enthusiastically
There was a move a few years ago to use titanium first stages. Titanium is tricky to ignite, but burns in nitrogen...
Vic.
[1] The appropriate gas to use is a religious argument rather than a technical one :-(
if the descending drones were paper aeroplanes it might be possible to make them so cheap that they are little more than "advanced packaging"
There's a group at Southampton University who are making paper planes and printing circuitry on them using conductive ink. There's going to be a way to go to make disposable delivery aircraft viable, but it's not beyond the realms of fantasy...
Vic.
That's already in patent law. They must actually produce the product or a competitor can challenge it on inactivity grounds.
[Citation needed], because if you were right, we would never have a problem with submarine patents.
AFAIK, The only inactivity that matters is a failure to take action against known infringers of a patent - which can reduce or remove the damages paid by the infringer if the court believes that inactivity was intended to lure the defendant into further infringement.
Vic.
Frankly, if this was such a good idea UPS, FedEx maybe even some post offices around the world would be working on it.
Vic.
The power needs would indeed be significant for calculations
Vic.
Including an order that went in on the evening of Wednesday the 21st and the box was in my hands on Christmas Eve
A few months back, I put in an order at about 8pm on a Friday evening. The box was delivered about noon the following day. I was most chuffed[1].
Vic.
[1] Especially as I'd gone for the free delivery option. And because it was a case of wine.
A stray drone that malfunctions and flies into the path of an airliner that is landing or taking off could have some, shall we say, interesting results.
It doesn't even need to do that. A stray drone that appears to be heading towards controlled airspace without clearance is enough to trigger the re-routing of many aircraft - with each diversion tending to cause additional diversions in order to maintain separation. It's a mess.
I went to a GasCo safety evening a few weeks back where they showed a NATS video[1] of a light aircraft flying first through Stansted's airspace and then through Heathrow's. Many flights were diverted, which was quite impressive, but I couldn't help but think "bullshit; this would never really happen"; I mean, the aircraft even lined up on the Heathrow runway. And then, at the end, they told us that all the positional data was from real radar traces...
Vic.
[1] Can't find it on the web at the mo - I'll post a link if/when I do.
at the rugby while delivering
Most aircraft are explicitly prohibited from such events - UK Air Law requires at least 1000ft distance to large groups of people, and the US seems to have the same rule (as you'd expect - aviation is well-standardised). So delivering to the rugby would require either specific permission for each flight (which will take months, not minutes), or a change in Aviation Law[1] in every country in which they want to operate.
This just isn't going to happen.
Vic.
[1] With all the corresponding fallout from having legislation now different to everyone else...
I only knew Lester through his work here. That's probably for the best - we;d have got drunk and punched each other out. My sort of bloke...
We owe it to him to get LOHAN launched. Is anyone running this now? If not, we need to put a team together to deal with the bureaucracy. Lester and the rest of the team have done the hard work - let's get the thing airborne. Ariadne's going to be a teenager before we know it...
I'll happily volunteer my meagre skills to further the project. Anyone else?
Vic.
could it be that diverting means landing in an unfamiliar airport and there is added risk ?
There are more risks than that.
For example, a passenger jet early in its flight is carrying loads of fuel. That's a lot of weight, and it is commonplace for such aircraft to be too heavy to land until they've burnt off some of it. So what do you do when a precautionary landing is required? The aircraft might not be equipped for fuel dumping.
Vic.
You never know. I came from the US into Australia, with an 16bit ISA card, along with cables, and they didn't bat an eyelid.
I was flying quite a bit after the Lockerbie attack, when they decided that electronics were an issue - although they really meant "batteries".
I would be carrying a couple of Eurocards. They would always be taken off me and swabbed...
Vic.
it is not only taking inordinate time for qualified specialists to debunk it
Not really.
The basis of this "drive" is that everything we thought we knew about physics is wrong. Thus, to test it, we cannot rely on physics. That means someone needs to build one and put it (largely) outside a gravity well where the tiny forces alleged to be involved might have any significance. And that means getting funding.
I think it's gone quite swiftly.
Vic.
Honorably, tests were done and the idea abandoned.
Tests have been performed on the "EM Drive".
The one that most interested me showed a thrust when the power was turned on. Then, they rotated the equipment and tried again - the same thrust was seen in the same orientation.
That puts the whole thing into the realm of "experimental error", AFAICS. I'd love to be proven wrong, but I'm pretty sure I won't be.
Vic.
I've got to insist that SSR isn't radar insofar as the information gained by SSR is not derived from the reflected transmitter signal,
You insist away. Radar is not defined as using a reflected pulse - that just happens to be the most prevalent type. RADAR stands for RAdio Detection And Ranging - which is exactly what SSR does. That's why it is called Secondary Surveillance Radar.
the difference between the A, B, C, D & S modes used by SSR is the timing of the interrogation pulses - the individual pulses themselves contain no information and are identical but the difference in timing between them tells the aircraft transponder which information is being requested
That's complete nonsense. Just wrong. The difference between the modes is primarily in the data returned by the transponder; mode S is the mode that permits selection of data returned, and that is by way of a phase-encoded value.
If you're going to define radar as any means of obtaining information about the state of an aircraft
I'm not. I'm defining radar as a means by which the direction to an object is determines by a directional antenna pointing at that object, and the range to it determined by the delay between the transmitted pulse and the received pulse.
And that is what SSR does.
Vic.
Currently, commercial aircraft are tracked via a system named Secondary Radar, which isn't really radar at all;
SSR generally[1] is radar. Modes A and C contain no positional information, so the situation you describe could only work if every aircraft in the controlled space were equipped with Mode S. That isn't the case.
I suspect you might be describing ADS-B, which is a fairly similar technology. It's very useful for collision avoidance, but it doesn't replace radar.
Vic.
[1] I have to say "generally" because I haven't personally checked every single entity in the world that describes itself as SSR. But everywhere I've flown that uses it does indeed use a radar.
I would be interested to hear whether a pilot would prefer to receive verbal instructions as necessary, rather than have yet another screen in front of them full of extraneous information.
CPDLC is already in use in commercial aviation. This story is about changing the communications medium to increase range rather than adding any new messaging system.
Vic.
"replace exactly the functionality the current solution provides, nothing more, but be designed so that it can be incrementally extended with new functionality".
"Nothing new, but something new". That's the sort of vague requirement that leaves the project undeliverable and yet still massively over-budget...
Vic.
If they were lukewarm about it, why take it to the Supreme Court?
Because if they don't, someone will inevitably question the legitimacy of any vote in Parliament over the issue. And so the noise continues...
By taking it to the Supreme Court, there will be one of two possible outcomes :-
Either of these outcomes is good for the Government.
Vic.
He being the boss, machine was cleaned up and nothing said.
I had a customer a while back that suffered repeated malware infections. They all came from the machine in the boss's office.
We ended up building him a dedicated Linux machine for his porn surfing - it was much cheaper that way...
Vic.
However, rowhammer is merely an example of a class of exploits that lie outside "state space analysis" (such as checking all inputs and outputs...) of a system.
No, it isn't. It's an example of an attack that lies outside a simplistic analysis; it's the sort of thing that would be found and flagged by anyone doing a more in-depth analysis, and mitigation procedures developed. Almost as if the designers of high-reliability equipment knew what they were doing.
Now of course such development is significantly more time-consuming than the more simplistic stuff - which is why it's vastly more expensive, and only carried out when such security is deemed necessary. Which is why it's such a laugh when people keep calling for consumer software to be made high-reliability; yes, that would make your desktop OS free from bugs, but you'd never be able to afford it in the first place.
Like having unbreakable encryption, that is none the less broken because your CPU activity while decrypting gives clues to the keys and can be picked up by a hack into your sound card
Again, side-channel attacks are a known issue. They are completely preventable - if you're prepared to pay for the development. That adds at least an order of magnitude to your costs - how many people do you think insist on such software?
We get these possibilities because people invariably go for the cheapest option until it bites them in the arse. That's not going to change in the near future - indeed, it's going to get worse because so many commentators "know" that "these things are unpreventable", thus conditioning the populace to accepting flawed code. The real truth is that a sufficiently-motivated development team *could* produce that avoids all these issues - but they're the only ones that would ever use it, because everyone else would be using something much cheaper that was available much earlier, and won't listen when told of its vulnerabilities.
And you only find out about it if the exploits are public
No, you find out about it when you put the effort into discovering how reliable your system is. Most vendors get that feedback form the field - but it woud be entirely possible for them to have found out before release, were they prepared to put the effort (=money) into doing so.
Vic.
Well the IFE gets an arrival time from somewhere.....and I think it's the Flight Management computers.So maybe not.
But the data is updated periodically, rather than in real-time.
Almost as if it's being gathered from a data carousel transmission from the FMS, rather than being requested...
Vic.
Given that security is hard for experts, some concern is warranted about the security of avionics, etc.
Whilst this is, of course, completely true, it should also be considered that a bunch of anonymous people on an Internet forum may not actually be in quite such a good place to judge the security of the systems as the people who work on them every day and warrant that they are, indeed, secure.
Vic.
Nobody has *ever* managed to make a computer system which they are *certain* is secure and is actually secure. Ever.
I have.
The interface was very simple, and fully characterised. The computer itself was welded into a metal box and dropped into very deep water - I was never allowed to know how deep, nor where it went.
That was a long time ago. I don't know if it's still there, nor even where "there" is. But I do know that it lasted the duration of the project and handled all inputs properly, since it had to be proven that it would before we committed to the final PCB.
Vic.
Even if (and I highly doubt this being the case on any modern system) you had a full state machine layout of your entire system and thus could make some assertions that no unexpected states existed, this would still overlook issues outside the logical system state that stray into physics territory (such as the ramhammer technique).
I'm assuming you meant rowhammer, rather than ramhammer.
Rowhammer doesn't work over RS-232...
As a result, I would take askance at any assertions of 100% security, for any kind of interface where information is passed between two systems.
I wouldn't. High-reliability systems have been built for decades - I've built some of them. Whether the current crop of avionics can be considered high-reliability is not something I could answer, not having been in that industry for a few years - but that doesn't mean they couldn't be.
Vic.
In academia you also get the problem of having to reproduce, for comparison, results someone got in 1989 with C code written for a SunOS 4 machine that was under their desk.
I rather like jobs like that. I have a fair-sized library of obsolete old hardware (including quite a bit of IPC/IPX) :-)
Vic.
if i were designing i mine id have it go off straight away with the initial downward pressure.
Your design kills one man.
The fire-on-release trigger delays at least three men, if not the whole squad, making them easy pickings for snipers.
And then it kills the same initial man, as well as probably killing or maiming the two who came to his aid. And if they're maimed, that ties up yet more men getting them medical attention.
War is ugly, but it would be very arrogant indeed to imagine you can out-think a weapons designer.
Vic.
I was horrified when I first encountered continental plugs/sockets with their piece of springy iron wire as the earth contact.
I did a trade show in Paris some years back. We paid a fairly hefty surcharge to have a 15A feed to the stall. I was less than impressed to find they hadn't fitted one - our kit required electricity.
I called the electrician, who confirmed that we did indeed have a 15A supply. I was buggered if I could find it, so I got him to come to the stand to show me where lay this mythical cable.
He pointed to a bit of bell wire sticking through the carpet...
Vic.
Why cannot the Royal Navy use the Lightning II C.
Because we don't have a carrier that can accommodate it.
Could this aircraft take off from a ramp and land using arrestor gear?
Yes, but you'll need a catapult as well. We don't have any carriers with catapults any more.
Could the angled deck have an electro catapult so it could operate more types of aircraft?
Yes. But BAe Systems want as much money to convert the current carriers to use EMALS as we paid to build them in the first place.
We haven't got that sort of cash to throw around at the moment. And even when the next election comes around, I don't think Maidenhead has enough to do with ship-building for it to happen.
Vic.
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