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PostPosted: Tue Jul 27, 2010 13:17 
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It is important that we can check the black boxes used by the police, and a start would be to have the source code used by them:

http://yourfreedom.hmg.gov.uk/restoring ... he-police#

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PostPosted: Tue Jul 27, 2010 13:25 
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not sure i entirely agree with that statement.


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PostPosted: Tue Jul 27, 2010 13:34 
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ed_m wrote:
not sure i entirely agree with that statement.


Nor do I. Provided that there a proper published specification for the device and they are independently tested against that specification the inner workings are irrelevant. My life - rather more important than a clean driving licence - depends, from time to time, on devices whose operation I do not fully understand but I am content that they are properly specified and tested.

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PostPosted: Tue Jul 27, 2010 13:52 
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dcbwhaley wrote:
ed_m wrote:
not sure i entirely agree with that statement.


Nor do I. Provided that there a proper published specification for the device and they are independently tested against that specification the inner workings are irrelevant. My life - rather more important than a clean driving licence - depends, from time to time, on devices whose operation I do not fully understand but I am content that they are properly specified and tested.


Blind faith is clearly one solution, but not mine.

For example, are you happy with the algorithms used by the LTI 20-20 LASER speed gun?

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PostPosted: Tue Jul 27, 2010 17:23 
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trakgalvis wrote:
For example, are you happy with the algorithms used by the LTI 20-20 LASER speed gun?


I don't give a monkeys about the algorithms used so long as the instrument works properly. Are you happy with the algorithms used in the ABS system in a car you use? Or in your television set? Or your mobile phone? You will certainly save a lot of money if you only buy consumer goods where all the firmware is openly published.

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PostPosted: Tue Jul 27, 2010 17:34 
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dcbwhaley wrote:
trakgalvis wrote:
For example, are you happy with the algorithms used by the LTI 20-20 LASER speed gun?


I don't give a monkeys about the algorithms used so long as the instrument works properly. Are you happy with the algorithms used in the ABS system in a car you use? Or in your television set? Or your mobile phone? You will certainly save a lot of money if you only buy consumer goods where all the firmware is openly published.


The example I gave is one in which the algorithm is suspect, and we could prove it, if we had the code. Sometimes the easiest way to spot a fault is to see the code. There are in fact many devices for which the code is open source, and I am amazed that you do not seem to know this.

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PostPosted: Tue Jul 27, 2010 18:24 
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trakgalvis wrote:
The example I gave is one in which the algorithm is suspect, and we could prove it, if we had the code.


so either the requirements aren't properly defined... or the specification doesn't meet the requirements... or the validation is incomplete/incorrect ?

if the above trail is available i don't think i care about the algorithm.
there's probably a good chance some of it is IP sensitive too.


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PostPosted: Tue Jul 27, 2010 23:46 
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trakgalvis wrote:
The example I gave is one in which the algorithm is suspect, and we could prove it, if we had the code.

If the algorithm is faulty the device - any device - will not operate according to specification. Testing against specification is the way that you check an instrument; not by taking it apart and staring at the entrails.

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PostPosted: Wed Jul 28, 2010 00:14 
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dcbwhaley wrote:
If the algorithm is faulty the device - any device - will not operate according to specification. Testing against specification is the way that you check an instrument; not by taking it apart and staring at the entrails.

And if the specification is lacking? (e.g. it doesn't 'test the negative', meaning no attempts at inducing undetected faults)

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PostPosted: Wed Jul 28, 2010 07:58 
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dcbwhaley wrote:
trakgalvis wrote:
The example I gave is one in which the algorithm is suspect, and we could prove it, if we had the code.

If the algorithm is faulty the device - any device - will not operate according to specification. Testing against specification is the way that you check an instrument; not by taking it apart and staring at the entrails.


I never did say that having the source code was to replace testing. However, having the source code does provide an additional way to find faults.

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PostPosted: Wed Jul 28, 2010 08:17 
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trakgalvis wrote:
I never did say that having the source code was to replace testing. However, having the source code does provide an additional way to find faults.

...it also gives the accused the ability to look for intentional tricks in the software. Imagine if there was some sort of secret "demo mode" whereby you could pre-enter a target speed yet the speed-gun operated "normally" capturing video etc. until it got a successful "ping" whereby it reported the "demo" speed rather than the actual? Just a few miles per hour over the limit wouldn't attract attention and would be very hard to disprove especially at a distance - pseudo-conviction rates could soar!!

And before anyone shouts "conspiracy theory", wasn't their a Formula One team that implemented (a banned) "launch control" on their cars a few years ago? Nothing in the "specification", nothing on the "menus", but a hidden button sequence that activated this secret capability - and it was only discovered by looking at the source code.

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PostPosted: Wed Jul 28, 2010 08:23 
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trakgalvis wrote:
I never did say that having the source code was to replace testing. However, having the source code does provide an additional way to find faults.


I would be very surprised if you could extract much information from the bare source code, without cooperation from the design engineers.

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PostPosted: Wed Jul 28, 2010 08:24 
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dcbwhaley wrote:
trakgalvis wrote:
I never did say that having the source code was to replace testing. However, having the source code does provide an additional way to find faults.[/quot

I would be very surprised if you could extract much information from the bare source code, without cooperation from the design engineers.


Really? Why? I would very much bet in the case of the LTI 20-20 that I could get a lot.

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PostPosted: Wed Jul 28, 2010 09:32 
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dcbwhaley wrote:
I would be very surprised if you could extract much information from the bare source code, without cooperation from the design engineers.

We've recently had to do just that several times where I work (we get lumbered with stuff from closed design centres), and one of those was internal, undocumented code.
Decent software engineers leave comments within their code to make it easier for others (and themselves) to pick up.

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PostPosted: Wed Jul 28, 2010 10:00 
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When I was bitching about a pool car I use at work, a Peugeot 206, and how there is a delay in the braking I was fobbed off by the dealer. :x

It’s not something I could do but I’m sure someone could unpick, (or un-PIC), what is going on and prove what I know to be true about it.

Interesting discussion :)

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PostPosted: Wed Jul 28, 2010 10:04 
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Steve wrote:
dcbwhaley wrote:
I would be very surprised if you could extract much information from the bare source code, without cooperation from the design engineers.

We've recently had to do just that several times where I work (we get lumbered with stuff from closed design centres), and one of those was internal, undocumented code.
Decent software engineers leave comments within their code to make it easier for others (and themselves) to pick up.


Also, in the particular case of the LTI 20-20, we are not expecting very complex code. It is true that working on the code of others is never easy, but that is not saying it is impossible. Steve is right that if the code was made by good programers, it should be filled with comments. For me, certain parameters in the error trapping software would be of great value to understand its flaws.

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PostPosted: Wed Jul 28, 2010 10:19 
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Big Tone wrote:
When I was bitching about a pool car I use at work, a Peugeot 206, and how there is a delay in the braking I was fobbed off by the dealer. :x

It’s not something I could do but I’m sure someone could unpick, (or un-PIC), what is going on and prove what I know to be true about it.

Interesting discussion :)


Indeed, you may be right here.

For a more extreme example, see: http://www.governmenttransparency.net/s ... 89#post389

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PostPosted: Wed Jul 28, 2010 10:32 
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Having read your link I’m more convinced than ever. You have my vote on this trakgalvis. :)

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PostPosted: Wed Jul 28, 2010 10:47 
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Steve wrote:
We've recently had to do just that several times where I work (we get lumbered with stuff from closed design centres), and one of those was internal, undocumented code.

So have I and it isn't easy.

Quote:
Decent software engineers leave comments within their code to make it easier for others (and themselves) to pick up.

But if. as OP, is suggesting there is some nefarious secret code in the device it is hardly likely to be commented with "This is the bit where we deliberately put in inaccuracies so the the user can get more hits" is it? Any half decent engineer could hide it behind a maze of spaghetti code and computed goto's. Indeed, many less than half decent designers do that routinely to all their code :) .

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PostPosted: Wed Jul 28, 2010 10:48 
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Big Tone wrote:
Having read your link I’m more convinced than ever. You have my vote on this trakgalvis. :)


I am pleased to hear it! :)

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