Xerox Confirms To David Kriesel Number Mangling Occuring On Factory Settings

An anonymous reader writes with a followup to last week's report that certain Xerox scanners and copiers could alter numbers as they scanned documents: "In the second Xerox press statement, Rick Dastin, Vice President at Xerox Corporation, stated: 'You will not see a character substitution issue when scanning with the factory default settings.' In contrast, David Kriesel, who brought up the issue in the first place, was able to replicate the issue with the very same factory settings. This might be a serious problem now. Not only does the problem occur using default settings and everyone may be affected, additionally, their press statements may have misled customers. Xerox replicated the issue by following Kriesel's instructions, later confirming it to Kriesel. Whole image segments seem to be copied around the scanned data. There is also a new Xerox statement out now." Swapping numbers while copying may seem like bizarre behavior for a copier, but In comments on the previous posting, several readers pointed out that Xerox was aware of the problem, and acknowledged it in the machine's documentation; the software updates promised should be welcome news to anyone who expects a copier to faithfully reproduce important numbers.

Comments

Re:Sucky thing about digital

[Gaygirlie]

Copying is still high quality.

Incorrect. The way these Xerox - machines work is that they first scan the document, then compress it and store it on the storage medium, and then use that compressed file to print out the copy from. It's braindead.

Re:Notify Xerox First

[ThreeKelvin]

It isn't a security issue so the only purpose served by his going public without him contacting Xerox is to stroke his ego.

It isn't a security problem? Seriously?

What if a doctor copies a prescription or your medical journal? Government officials copies personal information for use with a visa? Police officers copies statements? Or any other place where you'd want to copy something, that must be copied correctly?

Sure, it's not a computer security issue, but it's definitly, among other things, a security issue.

Re: Do you work for Xerox?

[Anonymous Coward]

I am a Xerox technician.

Yes, some models store and compress jobs before printing.

This problem may affect more than just Xerox...

[Colin Douglas Howell]

An earlier blog posting from Kriesel on this issue says that a reader reported similar behavior from a Brother copier:

http://www.dkriesel.com/en/blog/2013/0808_number_mangling_not_a_xerox-only_issue

And one of the comments to that posting says:

I have experimented with the open source jbig2enc library available at http://github.com/agl/jbig2enc, which has a encoding parameter called the “threshold”, described like this:

“sets the fraction of pixels which have to match in order for two symbols to be classed the same. This isn't strictly true, as there are other tests as well, but increasing this will generally increase the number of symbol classes”

The included command tool accepts values for this parameter between 0.4 and 0.9, with 0.85 as the default.

I have found replaced digits in single-page numerical tables encoded with this parameter set as high as 0.82. As with the other examples you have found, the errors are not in any ways obvious to the eye which is, of course, the real problem.

Since JBIG2 has been supported in PDF since 2001, it would be surprising if only Xerox have fallen into this trap.

Re:My reaction:

[squiggleslash]

It's the scanner bit. Basically it applies a heavy amount of compression to the final result by looking for blocks that match and duplicating them. Which is all fine until the copier sees what it thinks is a 0 but is actually an 8.