Bar codes. They're little bunches of black lines which can be read by a 
scanner. Right?

Hahaha, well... it turns out there are actually a miriad of different 
kinds. And they're ALL COMPLETELY DIFFERENT to each other.

I just did a cursory scan of my office. Here's what I found:

   Fruit bottle: EAN-13 barcode.
   Can of Dust-off: UPC-A barcode.
   Diary: EAN-13 barcode.
   SIIG USB-serial box: UPC-A barcode plus one of unknown type.
   StarTech USB-serial box: UPC-A barcode.
   Imation CD-R box: UPC-A barcode.
   Maxtor drive: 5 barcodes of unknown type.
   Integral RAM box: One barcode (from Insight UK) of unknown type.
   TNT shipping box: Two barcodes of unknown type.
   Gobel, Escher, Bach: EAN-13 barcode.
   Integral USB HD box: EAN-13 barcode.
   Other USB HD box: EAN-13 barcode.
   HP laptop adaptor: 3 barcodes of unknown type.

It's actually surprisingly hard to find barcodes. Usually you purposely 
ignore them, so when you *want* to see them they're actually quite hard 
to find.

It's great fun. EAN-13 is apparently an "extension" of UPC-A, and yet 
it's COMPLETELY DIFFERENT. The encoding is entirely unrelated. Of 
course, EAN-13 and UPC-A only encode digits. (And these digits encode a 
manufacturer ID and product ID.) Other codes can encode various 
additional characters. In particular, Code39 and Code128 allow text as 
well as digits.

The impressive thing is, as far as I can tell, almost all barcode 
scanners support almost all kinds of barcodes. Even though each coding 
scheme is utterly unrelated to any of the others. God only knows how 
this is physically possible...

Post a reply to this message

On 10/13/2009 10:23 AM, Invisible wrote:

> scheme is utterly unrelated to any of the others. God only knows how
> this is physically possible...

usually using a diode laser, a rotating mirror and a photo sensor, which 
turns photons into electrons, where the circuitry then interprets the 
variations of electron flow into digital signals, which is then 
processed by a processor, running software that can interpret the 
encoding schemes of many different types of barcodes. It then sends 
signals (either by RS-232 or USB protocol) to the computer, a device 
driver reads the incoming signal, and interprets the signals as a series 
of characters, output to the desired application.
-- 
~Mike

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Isn't there some bars at the beginning or the end that indicate the encoding ?

Post a reply to this message

Invisible schrieb:

> The impressive thing is, as far as I can tell, almost all barcode 
> scanners support almost all kinds of barcodes. Even though each coding 
> scheme is utterly unrelated to any of the others. God only knows how 
> this is physically possible...

Not much magic in there.

Barcodes are designed to have a lot of redundancy, so that reading 
errors can be detected.

So a barcode scanner just checks whether the code it just read makes 
sense (i.e. check digits match etc.) when interpreted as any of the 
codes it supports.

Conflicts seldom occur /because/ the barcodes are so dissimilar. Still, 
it is a good idea to configure the scanner to recognize only barcodes 
you actually expect to use, especially if you expect to work with 
barcodes that may be smudged or otherwise messed up.

Post a reply to this message

Gyscos schrieb:
> Isn't there some bars at the beginning or the end that indicate the encoding ?

No, not really. Though many barcodes include some "frame" to (a) 
identify the side at which the barcode starts, and/or (b) calibrate for 
the size of the barcode; such frames can often double-act to prevent 
misinterpreting other barcode types.

For instance, Code39 IIRC always starts and ends with the bars it uses 
for the Asterisk (*).

EAN-13, on the other hand, uses one pair of simple bars at the 
beginning, end, and in the middle, respectively, to calibrate for size, 
while the reading direction can unambiguously be inferred from any 
"character" of the barcode "payload".

But these "frames" are only standardized for each individual barcode 
type, and there is no universal scheme to identify the type. All you can 
do is test for which types of barcode this particular specimen reads 
without error.

Post a reply to this message

> It's great fun. EAN-13 is apparently an "extension" of UPC-A,

Those are used in supermarkets mainly, which is why you find them on all 
products sold to the public.

For non-public uses (eg on shipping cartons, internal parts of products etc) 
the company is obviously free to make up or use their own standard for the 
bar code.  You didn't find any 2D barcodes?

Post a reply to this message

scott wrote:
>> It's great fun. EAN-13 is apparently an "extension" of UPC-A,
> 
> Those are used in supermarkets mainly, which is why you find them on all 
> products sold to the public.

Yeah, apparently UPC-A is for America, EAN-13 is supposedly for 
everywhere, but almost all scanners support both. They can only encode 
numbers though - usually standardised product codes.

> For non-public uses (eg on shipping cartons, internal parts of products 
> etc) the company is obviously free to make up or use their own standard 
> for the bar code.

Yeah, the shipping box I've got has several extremely wide barcodes. 
These codes encode letters as well, but I can't determine exactly which 
system they are. (Assuming they're even a standard one...)

> You didn't find any 2D barcodes?

None.

However... The Royal Mail allow you to print your own stamps, for a fee. 
You give them money, they give you a PDF file containing a 2D barcode 
[which presumably encodes the date of purchase, since it apparently 
expires after so many days].

Now I'm thinking... it appears to be a standard Data Matrix barcode, so 
if I could figure out WTF the data encoded in it is, I could print as 
many of them as I like, without a fee...

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Interesting fact: I actually have a barcode scanner here. Specifically, 
our tape robot has a barcode scanner. We've never used it, but 
apparently our Director of IT has suddenly decided that we're going to. 
In a few days' time I should have a stack of preprinted barcode labels.

I wonder what kinds the scanner can read?

Post a reply to this message

> Now I'm thinking... it appears to be a standard Data Matrix barcode, so if 
> I could figure out WTF the data encoded in it is, I could print as many of 
> them as I like, without a fee...

Won't they encode a serial number in there? As soon as they detect a 2nd 
stamp in the system with the same serial number (or with one they know they 
haven't sold yet) there will be trouble.

Also it probably has some checksum, you'd need a shed load of stamps to 
figure it out probably.

And hope they don't encode your IP address or payment details in there too.

A bit like that system on Blu-Ray discs, where every player plays back a 
very slightly different version, so when someone rips and uploads to 
BitTorrent, they can tell exactly which player it was ripped from.

Post a reply to this message

>> Now I'm thinking... it appears to be a standard Data Matrix barcode, 
>> so if I could figure out WTF the data encoded in it is, I could print 
>> as many of them as I like, without a fee...
> 
> Won't they encode a serial number in there? As soon as they detect a 2nd 
> stamp in the system with the same serial number (or with one they know 
> they haven't sold yet) there will be trouble.

Yeah, this is probably the main problem. If they know which numbers 
they've actually sold and which ones have actually been used, there's 
not much you can do.

> Also it probably has some checksum, you'd need a shed load of stamps to 
> figure it out probably.

Well, if you were going to reverse-engineer it, sure. But if you could 
figure out the algorithm...

It's like Windows license keys. Each one is a 20-character alphanumeric 
string. There must be some algorithm that Windows uses to decide whether 
the key you just entered is valid. If you somehow knew what that 
algorithm is.......

> And hope they don't encode your IP address or payment details in there too.

If you *knew* how they generate the barcode, you could put an arbitrary 
IP address in there. (Besides, knowing somebody's IP address doesn't 
really tell you a whole heap.) Payment details might be more fun...

> A bit like that system on Blu-Ray discs, where every player plays back a 
> very slightly different version, so when someone rips and uploads to 
> BitTorrent, they can tell exactly which player it was ripped from.

Really? That's news...

Post a reply to this message

>> Also it probably has some checksum, you'd need a shed load of stamps to 
>> figure it out probably.
>
> Well, if you were going to reverse-engineer it, sure. But if you could 
> figure out the algorithm...

How are you going to figure out the algorithm without access to lots of 
stamps you know are valid?

> If you *knew* how they generate the barcode, you could put an arbitrary IP 
> address in there.

Isn't the problem here that you're trying to work out how to generate the 
barcode?

>> A bit like that system on Blu-Ray discs, where every player plays back a 
>> very slightly different version, so when someone rips and uploads to 
>> BitTorrent, they can tell exactly which player it was ripped from.
>
> Really? That's news...

http://www.freedom-to-tinker.com/tags/aacs?page=1

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>>> Also it probably has some checksum, you'd need a shed load of stamps 
>>> to figure it out probably.
>>
>> Well, if you were going to reverse-engineer it, sure. But if you could 
>> figure out the algorithm...
> 
> How are you going to figure out the algorithm without access to lots of 
> stamps you know are valid?

I suppose the fatal assumption here is that the encoding of the 
information into the barcode is trivial. If these guys are sensible, it 
won't be...

>>> A bit like that system on Blu-Ray discs, where every player plays 
>>> back a very slightly different version, so when someone rips and 
>>> uploads to BitTorrent, they can tell exactly which player it was 
>>> ripped from.
>>
>> Really? That's news...
> 
> http://www.freedom-to-tinker.com/tags/aacs?page=1

Interesting. So the film actually ends a different way depending on 
which player you play it with?

I bet that'll be popular...

[But then again, all these copywrite notices and "piracy is stealing" 
ads and aggressive copy-protection systems only piss off paying 
customers. They have no effect on criminals...]

Post a reply to this message

> Interesting. So the film actually ends a different way depending on which 
> player you play it with?
>
> I bet that'll be popular...

LOL, I suspect they can do it slightly more subtly than that!  They only 
need to make some tiny changes to some of the pixels to be detectable.  In 
theory they could do what you suggest though, would be fun :-)

Post a reply to this message

>> Interesting. So the film actually ends a different way depending on 
>> which player you play it with?
>>
>> I bet that'll be popular...
> 
> LOL, I suspect they can do it slightly more subtly than that!  They only 
> need to make some tiny changes to some of the pixels to be detectable.  
> In theory they could do what you suggest though, would be fun :-)

Well, the article states that it's supposed to resist somebody pointing 
a video camera at their TV screen, so a 1-pixel alteration won't do.

What I suppose they might do is have maybe a 1-frame difference in how 
long a given scene is. Like, on some disks the shot of the ocean is 1362 
frames long, and on others it lasts for 1366 frames. The difference 
should be reliably detectable no matter how you film it.

Still, it seems like a hell of a lot of work considering that it doesn't 
actually stop illegal copying, it just makes it hypothetically possible 
to find out who did the illegal copying...

Post a reply to this message

scott wrote:
> BitTorrent, they can tell exactly which player it was ripped from.

With the understnading that a "player" in this context means "model number" 
at least in the hardware players. I.e., they can tell it got ripped by a 
Sony XYZ-1230 brand blu-ray player, not Joe's blu-ray player.

The idea is to identify it enough to black list the leaked keys, not to 
catch the person who distributed the movie.

-- 
   Darren New, San Diego CA, USA (PST)
   I ordered stamps from Zazzle that read "Place Stamp Here".

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Invisible wrote:
> Well, the article states that it's supposed to resist somebody pointing 
> a video camera at their TV screen, so a 1-pixel alteration won't do.

Probably different watermarks encoded, without actually looking visibly 
different in a way you could tell. Otherwise, someone might just rip it 
twice and change the file to use (say) 1364 frames of ocian.

-- 
   Darren New, San Diego CA, USA (PST)
   I ordered stamps from Zazzle that read "Place Stamp Here".

Post a reply to this message

>> Well, the article states that it's supposed to resist somebody 
>> pointing a video camera at their TV screen, so a 1-pixel alteration 
>> won't do.
> 
> Probably different watermarks encoded, without actually looking visibly 
> different in a way you could tell. Otherwise, someone might just rip it 
> twice and change the file to use (say) 1364 frames of ocian.

Well, to lots of people digital watermarking is the Holy Grail of 
digital technology, the thing that will finally stop the pirates. 
Trouble is... it's extremely hard.

If the watermark is encoded in a way that's perceptually 
insignificant... well guess what lossy codecs are specifically designed 
to do? Yes, that's right: *remove* perceptually insignificant information!

I'm thinking things like small timing differences would be too subtle to 
notice, but significant enough for encoding to not screw them up. And 
you could try to correct it yourself, but you'd have to know exactly 
which bits of timing are varied in order to know what to change...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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>> BitTorrent, they can tell exactly which player it was ripped from.
> 
> With the understnading that a "player" in this context means "model 
> number" at least in the hardware players. I.e., they can tell it got 
> ripped by a Sony XYZ-1230 brand blu-ray player, not Joe's blu-ray player.
> 
> The idea is to identify it enough to black list the leaked keys, not to 
> catch the person who distributed the movie.

The article suggests that the system *is* supposed to be able to narrow 
it down to a specific machine or possibly a small number of such 
machines, not just a specific model.

Of course, it depends on whether the makers bother to fit each player 
with semi-unique keys or not... One commenter pointed out that hardware 
manufacturers have no vested interest in making DRM work. Only studios do.

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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Orchid XP v8 wrote:
> Trouble is... it's extremely hard.

Certainly.

> If the watermark is encoded in a way that's perceptually 
> insignificant... well guess what lossy codecs are specifically designed 
> to do? Yes, that's right: *remove* perceptually insignificant information!

Well, you can spread it across lots of media, a few bits at a time. Xerox 
had a mechanism where you could vary the spacing between words in a 
document, and encode maybe a couple dozen bits per page of a document, for 
example.

But yes, it's difficult. Anything else is open to fairly simple subversion, 
tho.

> I'm thinking things like small timing differences would be too subtle to 
> notice, but significant enough for encoding to not screw them up. 

Could be, until you convert PAL to NTSC. :-) What you'd want is to have 
something where it's difficult without the key to even know where the data 
is encoded.

> you could try to correct it yourself, but you'd have to know exactly 
> which bits of timing are varied in order to know what to change...

But you have the different pieces all on the disk. All you need is the keys 
from two different players and you can tell what's different.

-- 
   Darren New, San Diego CA, USA (PST)
   I ordered stamps from Zazzle that read "Place Stamp Here".

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Orchid XP v8 wrote:
> The article suggests that the system *is* supposed to be able to narrow 
> it down to a specific machine or possibly a small number of such 
> machines, not just a specific model.

No, that's what I'm saying.  "Player" in *this* context means a set of keys 
(obviously). Software players can each get a set of keys from the 
manufacturer when you install the machine. But people don't, in general, 
program a unique key into each hardware player.

-- 
   Darren New, San Diego CA, USA (PST)
   I ordered stamps from Zazzle that read "Place Stamp Here".

Post a reply to this message

On Wed, 14 Oct 2009 09:22:57 +0100, Invisible wrote:

> Now I'm thinking... it appears to be a standard Data Matrix barcode, so
> if I could figure out WTF the data encoded in it is, I could print as
> many of them as I like, without a fee...

Until you got caught, that is, and fined/put in jail for fraud.... ;-)

Jim

Post a reply to this message

On Wed, 14 Oct 2009 17:17:25 +0200, scott wrote:

>> Interesting. So the film actually ends a different way depending on
>> which player you play it with?
>>
>> I bet that'll be popular...
> 
> LOL, I suspect they can do it slightly more subtly than that!  They only
> need to make some tiny changes to some of the pixels to be detectable. 
> In theory they could do what you suggest though, would be fun :-)

Probably a form of steganography, at a guess.

Jim

Post a reply to this message

Darren New schrieb:
> Orchid XP v8 wrote:
>> The article suggests that the system *is* supposed to be able to 
>> narrow it down to a specific machine or possibly a small number of 
>> such machines, not just a specific model.
> 
> No, that's what I'm saying.  "Player" in *this* context means a set of 
> keys (obviously).

What's obvious about that?

Hardware players are likely to have a Flash ROM or EEPROM anyway, so 
it's no technical problem to equip each individual player with a unique key.

And as for motivating manufacturers to do that, it might be a 
requirement of the license agreement they had to sign to implement 
BlueRay technology in the first place.

Software players, OTOH, typically seem to share a common Device Key for 
all installations of a particular player version.

At least that's what I read between the lines of the article.

Post a reply to this message

clipka wrote:
> Darren New schrieb:
>> Orchid XP v8 wrote:
>>> The article suggests that the system *is* supposed to be able to 
>>> narrow it down to a specific machine or possibly a small number of 
>>> such machines, not just a specific model.
>>
>> No, that's what I'm saying.  "Player" in *this* context means a set of 
>> keys (obviously).
> 
> What's obvious about that?

Because I've read more than just one article on the subject?  The point is 
to track down the key used to decrypt the content so the key can be added to 
the blacklists on future players.

> Hardware players are likely to have a Flash ROM or EEPROM anyway, so 
> it's no technical problem to equip each individual player with a unique 
> key.

The hardware players are required to have FLASH in them, because they need 
to update to new versions of blacklists. They're not (last I read) required 
to actually have a separate key per player.

> And as for motivating manufacturers to do that, it might be a 
> requirement of the license agreement they had to sign to implement 
> BlueRay technology in the first place.

It might. But it isn't.

> Software players, OTOH, typically seem to share a common Device Key for 
> all installations of a particular player version.

Typically they often do, but contractually they may be forced to provide a 
separate key for each player if the blu-ray licensing folks feel it's 
appropriate given the structure of the decoder in the software.


Read up more on how it all works. It's really quite impressively complex.

-- 
   Darren New, San Diego CA, USA (PST)
   I ordered stamps from Zazzle that read "Place Stamp Here".

Post a reply to this message

Darren New schrieb:

>>> No, that's what I'm saying.  "Player" in *this* context means a set 
>>> of keys (obviously).
>>
>> What's obvious about that?
> 
> Because I've read more than just one article on the subject?

Does that make it /obvious/ in this context? It may make it obvious to 
/you/, but that's a different story.

 > The point
> is to track down the key used to decrypt the content so the key can be 
> added to the blacklists on future players.

No. The point is to track down the key (as you say) to add it to the 
blacklist on future /discs/.


>> Hardware players are likely to have a Flash ROM or EEPROM anyway, so 
>> it's no technical problem to equip each individual player with a 
>> unique key.
> 
> The hardware players are required to have FLASH in them, because they 
> need to update to new versions of blacklists. They're not (last I read) 
> required to actually have a separate key per player.

What on earth should the players blacklist?

Unless the security stuff also contains an /additional/ mechanism to 
somehow identify pirated copies of movies. But that's not what the 
article is talking about.

Post a reply to this message

Darren New schrieb:

>> The article suggests that the system *is* supposed to be able to 
>> narrow it down to a specific machine or possibly a small number of 
>> such machines, not just a specific model.
> 
> No, that's what I'm saying.  "Player" in *this* context means a set of 
> keys (obviously). Software players can each get a set of keys from the 
> manufacturer when you install the machine. But people don't, in general, 
> program a unique key into each hardware player.

Not that Wikipedia would be free from error, but they explicitly state 
that having a different key for each /individual/ player is the major 
difference in key management between CSS (as used on DVD, having one key 
per player model) and AACS (having one key per individual player) - the 
idea apparently being that keys /can/ be revoked without hurting many 
honest consumers.

Post a reply to this message

> What I suppose they might do is have maybe a 1-frame difference in how 
> long a given scene is. Like, on some disks the shot of the ocean is 1362 
> frames long, and on others it lasts for 1366 frames. The difference should 
> be reliably detectable no matter how you film it.

I think there are lots of possibilities for things they could do.  When a 
disc is released that actually uses this feature, I'm sure lots of people 
will be jumping up and down trying to find the differences.

> Still, it seems like a hell of a lot of work considering that it doesn't 
> actually stop illegal copying, it just makes it hypothetically possible to 
> find out who did the illegal copying...

You know what they're like, they like to try and scare everyone with their 
copy protection schemes, plus they need somone to sue for $76578236597826457 
when they find a copy on bitTorrent.

Post a reply to this message

>> LOL, I suspect they can do it slightly more subtly than that!  They only
>> need to make some tiny changes to some of the pixels to be detectable. 
>> In theory they could do what you suggest though, would be fun :-)
> 
> Probably a form of steganography, at a guess.

Well, if they're hiding player ID information in the video, then that 
would, by definition, be "steganography". That's what steganography 
*is*, after all...

The question is which steganographic technique they'll use. ;-)

Post a reply to this message

>> Now I'm thinking... it appears to be a standard Data Matrix barcode, so
>> if I could figure out WTF the data encoded in it is, I could print as
>> many of them as I like, without a fee...
> 
> Until you got caught, that is, and fined/put in jail for fraud.... ;-)

Would they actually bother for 21p?

Now, if I wrote an automated program to print these stamps and posted it 
on the Internet... *then* they might have a case. :-P

Post a reply to this message

Invisible wrote:

> The impressive thing is, as far as I can tell, almost all barcode 
> scanners support almost all kinds of barcodes. Even though each coding 
> scheme is utterly unrelated to any of the others. God only knows how 
> this is physically possible...

It's actually very simple.  As long as the scanner is close enough, and 
is at the proper angle, all stripes of a given width will appear the 
same to the scanner.  Each bar coding system uses a series of different 
widths to represent each character.  Some systems use only narrow and 
wide stripes (double width), while others will have stripes that are 
three and four times the size of the narrowest stripe.  Generally each 
character is comprised of a set of stripes that add up to a constant 
width (or else the bar codes would appear to have different widths).

As you can see, once the series of widths is in the scanner, 
interpretation becomes a software issues.  If the data doesn't make 
sense under one coding scheme, the scanner can always run the same set 
of width data through another scheme.

Regards,
John

Post a reply to this message

On 10/15/2009 3:17 AM, Invisible wrote:
>>> Now I'm thinking... it appears to be a standard Data Matrix barcode, so
>>> if I could figure out WTF the data encoded in it is, I could print as
>>> many of them as I like, without a fee...
>>
>> Until you got caught, that is, and fined/put in jail for fraud.... ;-)
>
> Would they actually bother for 21p?

What would likely happen is the system would detect the stamp was 
already used, and kick it back to the sender with "Insufficient Postage" 
emblazoned across the stamp.


-- 
~Mike

Post a reply to this message

> What would likely happen is the system would detect the stamp was already 
> used, and kick it back to the sender with "Insufficient Postage" 
> emblazoned across the stamp.

I wonder if they even bother to check them against a database of already 
used/issued ones?  Maybe they just check the checksum?

There was a story a few years ago where a self-checkout machine in Tesco 
didn't do this for some voucher, and a guy just photocopied it hundreds of 
times and it worked :-)  Oh here I found it:

http://www.timesonline.co.uk/tol/news/uk/crime/article1572721.ece

Post a reply to this message

scott schrieb:

>> What would likely happen is the system would detect the stamp was 
>> already used, and kick it back to the sender with "Insufficient 
>> Postage" emblazoned across the stamp.
> 
> I wonder if they even bother to check them against a database of already 
> used/issued ones?  Maybe they just check the checksum?

The German "Post" has a similar system, and they /do/ check it against a 
database.

BTW, the German 2D "stamp" barcode even encodes the full destination 
address information, which has the benefit (for the "Post") of (a) 
rendering the stamp fundamentally un-reusable anyway except for mails to 
the same addressee, and (b) making the address even easier machine-readable.

Post a reply to this message

> The German "Post" has a similar system, and they /do/ check it against a 
> database.

I always wondered, if you posted a letter without a stamp in Germany and 
swapped the To/From addresses, would it get delivered to your intended 
recipient for free?

Post a reply to this message

clipka wrote:
> Darren New schrieb:
> 
>>>> No, that's what I'm saying.  "Player" in *this* context means a set 
>>>> of keys (obviously).
>>>
>>> What's obvious about that?
>>
>> Because I've read more than just one article on the subject?
> 
> Does that make it /obvious/ in this context? It may make it obvious to 
> /you/, but that's a different story.

It's obvious if you read the article in that context what they mean. I guess 
if you didn't know that, it's possible it was less obvious.

>  > The point
>> is to track down the key used to decrypt the content so the key can be 
>> added to the blacklists on future players.
> 
> No. The point is to track down the key (as you say) to add it to the 
> blacklist on future /discs/.

Yes. I misspoke. But the blacklist from those disks also goes into the 
players. (The blacklists being subtrees of the key tree.)

> What on earth should the players blacklist?

The players actually wind up blacklisting particular keys, IIRC. It's a 
highly complex system, and now that you mention it, I'm not sure I still 
remember all those details.

> Unless the security stuff also contains an /additional/ mechanism to 
> somehow identify pirated copies of movies. 

They do, but I don't think that has to do with the key stuff we're talking 
about, since they just *always* refuse to play pirated movies regardless.

-- 
   Darren New, San Diego CA, USA (PST)
   I ordered stamps from Zazzle that read "Place Stamp Here".

Post a reply to this message

clipka wrote:
> Not that Wikipedia would be free from error, 

It's possible what I've read was wrong too, yes. I've never licensed the stuff.

-- 
   Darren New, San Diego CA, USA (PST)
   I ordered stamps from Zazzle that read "Place Stamp Here".

Post a reply to this message

scott schrieb:
>> The German "Post" has a similar system, and they /do/ check it against 
>> a database.
> 
> I always wondered, if you posted a letter without a stamp in Germany and 
> swapped the To/From addresses, would it get delivered to your intended 
> recipient for free?

I guess that might depend on how far away the recipient is living. All 
letters are nowadays processed in one of dunno-how-many mail centers, 
and I reckon the first such center to handle any letter will check it 
for sufficient postage; if they find that the alleged sender address is 
not anywhere close to where the letter was posted (and I guess they can 
narrow that down comparatively well), but the alleged recipient is 
living surprisingly close nearby, someone might get suspicious.

So if you intend to send a letter to a friend living a few blocks away, 
and you're just too lazy to walk to their home and hand over the letter 
in person, this scheme might indeed work.

Post a reply to this message

On Thu, 15 Oct 2009 09:15:57 +0100, Invisible wrote:

>>> LOL, I suspect they can do it slightly more subtly than that!  They
>>> only need to make some tiny changes to some of the pixels to be
>>> detectable. In theory they could do what you suggest though, would be
>>> fun :-)
>> 
>> Probably a form of steganography, at a guess.
> 
> Well, if they're hiding player ID information in the video, then that
> would, by definition, be "steganography". That's what steganography
> *is*, after all...
> 
> The question is which steganographic technique they'll use. ;-)

One that's difficult to guess, I'd guess. :-)

Jim

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On Thu, 15 Oct 2009 09:17:02 +0100, Invisible wrote:

>>> Now I'm thinking... it appears to be a standard Data Matrix barcode,
>>> so if I could figure out WTF the data encoded in it is, I could print
>>> as many of them as I like, without a fee...
>> 
>> Until you got caught, that is, and fined/put in jail for fraud.... ;-)
> 
> Would they actually bother for 21p?

They'd probably fine you if they noticed it.

> Now, if I wrote an automated program to print these stamps and posted it
> on the Internet... *then* they might have a case. :-P

That would certainly raise your visibility, yes.  But breaking the law is 
breaking the law, and when one does it one has to be prepared for the 
consequences.  Thinking "yes, it's illegal but they won't care/will never 
catch me" - well, the prisons here (and there) are filled with people who 
thought that way.

Jim

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>> Would they actually bother for 21p?
> 
> They'd probably fine you if they noticed it.
> 
>> Now, if I wrote an automated program to print these stamps and posted it
>> on the Internet... *then* they might have a case. :-P
> 
> That would certainly raise your visibility, yes.  But breaking the law is 
> breaking the law, and when one does it one has to be prepared for the 
> consequences.  Thinking "yes, it's illegal but they won't care/will never 
> catch me" - well, the prisons here (and there) are filled with people who 
> thought that way.

Theoretically, if I pick up one of the pens at work and take it home 
with me, that's theft.

Is my employer going to care?

I doubt it...

(And a pen costs significantly more than a stamp.)

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On Thu, 15 Oct 2009 16:35:01 +0100, Invisible wrote:

>>> Would they actually bother for 21p?
>> 
>> They'd probably fine you if they noticed it.
>> 
>>> Now, if I wrote an automated program to print these stamps and posted
>>> it on the Internet... *then* they might have a case. :-P
>> 
>> That would certainly raise your visibility, yes.  But breaking the law
>> is breaking the law, and when one does it one has to be prepared for
>> the consequences.  Thinking "yes, it's illegal but they won't care/will
>> never catch me" - well, the prisons here (and there) are filled with
>> people who thought that way.
> 
> Theoretically, if I pick up one of the pens at work and take it home
> with me, that's theft.
> 
> Is my employer going to care?
> 
> I doubt it...
> 
> (And a pen costs significantly more than a stamp.)

I have worked for employers who did care about pens going home with 
employees.

It's a risk analysis, but as I said, the prisons are full of people who 
thought they could "get away with it" and were wrong.

Jim

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Invisible <voi### [at] devnull> wrote:
> Bar codes. They're little bunches of black lines which can be read by a
> scanner. Right?
>
> Hahaha, well... it turns out there are actually a miriad of different
> kinds. And they're ALL COMPLETELY DIFFERENT to each other.
>

My Android phone has an app that does a bar code scanner that can eventually
look up the product it scans online to see who sells it for what.  I've found
prices for things when looking up some very boring, unimportant things when I
tested it around the house. It has however failed me twice in computer stores
when I was hurriedly trying to find out if the price were right.  I quickly
scanned one of the five or six bar codes on the box and it never worked.  Maybe
some of these were about the UPS shipping or inventory. I never found the store
product UPC.

Post a reply to this message

gregjohn schrieb:

> My Android phone has an app that does a bar code scanner that can eventually
> look up the product it scans online to see who sells it for what.  I've found
> prices for things when looking up some very boring, unimportant things when I
> tested it around the house. It has however failed me twice in computer stores
> when I was hurriedly trying to find out if the price were right.  I quickly
> scanned one of the five or six bar codes on the box and it never worked.  Maybe
> some of these were about the UPS shipping or inventory. I never found the store
> product UPC.

It seems to me they don't bother about UPC-A (or EAN-13) codes except 
for products typically sold at supermarkets and other high-volume 
low-margin retailers.

I can imagine that it doesn't pay off for e.g. manufacturers in the 
computing industry to apply for a company code, as the customers have a 
strong say in what products a shop will carry (at least for the products 
the store will make the real money with), so the retailers have 
difficulties trying to threaten the manufacturers with boycotting their 
products. And most retailers will not really bother too much either, as 
the handling expenses are low compared to the margin.

Supermarkets, on the other hand, are strongly motivated to keep handling 
costs to a minimum, and it won't hurt them much if they refused to carry 
a certain brand of toothpaste.

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http://blog.wolframalpha.com/2009/10/09/what-does-that-barcode-say/

FAIL.

Altough... now I can *print* barcodes. (Just not *read* them.)

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Invisible wrote:
> Interesting fact: I actually have a barcode scanner here. Specifically, 
> our tape robot has a barcode scanner. We've never used it, but 
> apparently our Director of IT has suddenly decided that we're going to. 
> In a few days' time I should have a stack of preprinted barcode labels.

OK, so I now have several sheets of barcode labels.

What I can't figure out is which symbiology they use. Consider, for 
example, the label for "UKM11001L3". If 1=black and 0=white, we have

[...000]101101101001010101001101101100101011010110101001011010
11011001010101101100101011010100101101101010010110100101011
011011001010101101101010100110101101101001[000...]

This doesn't seem to match anything Wolfram Alpha can come up with:

http://www.wolframalpha.com/input/?i=barcode+UKM11001L3

None of these barcodes start with the distinctive two thin bars framing 
two thick bars ("...01011011010..."). I have no idea what barcode type 
this is...

Post a reply to this message

On 10/23/2009 8:58 AM, Invisible wrote:
> OK, so I now have several sheets of barcode labels.
>
> What I can't figure out is which symbiology they use. Consider, for
> example, the label for "UKM11001L3". If 1=black and 0=white, we have
>
> [...000]101101101001010101001101101100101011010110101001011010
> 11011001010101101100101011010100101101101010010110100101011
> 011011001010101101101010100110101101101001[000...]
>
> This doesn't seem to match anything Wolfram Alpha can come up with:
>
> http://www.wolframalpha.com/input/?i=barcode+UKM11001L3
>
> None of these barcodes start with the distinctive two thin bars framing
> two thick bars ("...01011011010..."). I have no idea what barcode type
> this is...

Why not upload a scan of the barcode?

Mike

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SharkD wrote:

> Why not upload a scan of the barcode?

I'd need a scanner to do that.

Post a reply to this message

Invisible wrote:
> SharkD wrote:
> 
>> Why not upload a scan of the barcode?
> 
> I'd need a scanner to do that.

A camera will do too.

Post a reply to this message

Invisible schrieb:

> OK, so I now have several sheets of barcode labels.
> 
> What I can't figure out is which symbiology they use. Consider, for 
> example, the label for "UKM11001L3". If 1=black and 0=white, we have
> 
> [...000]101101101001010101001101101100101011010110101001011010
> 11011001010101101100101011010100101101101010010110100101011
> 011011001010101101101010100110101101101001[000...]
> 
> This doesn't seem to match anything Wolfram Alpha can come up with:
> 
> http://www.wolframalpha.com/input/?i=barcode+UKM11001L3
> 
> None of these barcodes start with the distinctive two thin bars framing 
> two thick bars ("...01011011010..."). I have no idea what barcode type 
> this is...

Now if you think that those three barcodes on the Wolfram page are all 
the world has to offer...

http://www.herdsoft.com/ti/davinci4/examples/barcodecgi.cgi is convinced 
that it is a "Code 39" (aka "Code 3 of 9") barcode, and indeed correctly 
reads it as "UKM11001L3".

Closer analysis of your barcode pattern shows that your barcode indeed 
appears to be Code 39, but flipped horizontally for some reason (which 
of course should not matter to a barcode reader).

BTW, Wolfram is doing a poor job at generating Code 39 barcodes, as it 
uses different bar widths for the "frame" than for the "payload".

(The Code 39 frame is usually interpreted as a leading and trailing 
asterisk (*) character, as it uses the same bar sequence.)

Post a reply to this message

>> This doesn't seem to match anything Wolfram Alpha can come up with:
>>
>> http://www.wolframalpha.com/input/?i=barcode+UKM11001L3
>>
>> None of these barcodes start with the distinctive two thin bars 
>> framing two thick bars ("...01011011010..."). I have no idea what 
>> barcode type this is...
> 
> Now if you think that those three barcodes on the Wolfram page are all 
> the world has to offer...

There don't appear to be many bacode types that handle text. Many handle 
only numbers.

> http://www.herdsoft.com/ti/davinci4/examples/barcodecgi.cgi is convinced 
> that it is a "Code 39" (aka "Code 3 of 9") barcode, and indeed correctly 
> reads it as "UKM11001L3".

Really? (I can't even tell what language that page is in.)

> Closer analysis of your barcode pattern shows that your barcode indeed 
> appears to be Code 39, but flipped horizontally for some reason (which 
> of course should not matter to a barcode reader).

My word... That *does* in fact appear to match. I hadn't noticed that!

> BTW, Wolfram is doing a poor job at generating Code 39 barcodes, as it 
> uses different bar widths for the "frame" than for the "payload".
> 
> (The Code 39 frame is usually interpreted as a leading and trailing 
> asterisk (*) character, as it uses the same bar sequence.)

I especially love the way the bar widths don't appear to be multiples of 
each other. I almost wonder if the image has been scaled down by 
rounding each bar to a whole number of pixels, so some "thin" bars are 3 
pixels and some are 4... It's very districting!

Indeed, clicking on "PDF" and enlarging the image seems to make the 
problem go away... How annoying!

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