Today I came upon some news weird enough to justify a post on this long-dormant blog. Ars Technica reports that it “began on January 30 and afflicted Mazdas from model years 2014 to 2017 when the cars were tuned to the local NPR station, KUOW 94.9. At some point during the day’s broadcast, a signal from KUOW caused the Mazdas’ infotainment systems to crash—the screens died and the radios were stuck on 94.9 FM.”
That shouldn’t be possible, right? A broadcast FM signal is just frequency-modulated audio. It might deafen you or damage the speakers, but it shouldn’t make the receiver stop working! Well, actually, it isn’t just audio. Broadcasters can optionally use the Radio Broadcast Data System (RBDS), which supports encoded digital data. It uses a 57 kHz subcarrier, well above the limits of human hearing. The data is encoded at 1187.5 bits per second, a strange-sounding number that yields 48 cycles of the subcarrier for every bit. Error correction codes bring the effective data rate down to 730 bits per second.
I got a request for my ebook, JHOVE Tips for Developers. It’s no longer for sale on Smashwords, since I haven’t updated it since 2012, but if anyone wants it, you can download JHOVE Tips for Developers from this site.
Posted in News
The town of Windham, New Hampshire, became the site of a controversy when the results of a ballot recount by hand didn’t match the original results. This has some interesting implications for ballot scanning and errors in the process, so I think it’s fair game for this blog. I’ll have to get into the politics to give it context, though.
The four winning candidates for the state legislature were found to have gotten about 300 additional votes each, while the one who requested the recount got fewer, so the results weren’t affected. Still, it was appropriate to ask why the scanners’ total was so far off. The town accordingly had an audit conducted.
Waking up briefly to mention an interesting article…
In 1986, the RIAA was outraged that Sony’s Digital Audio Tape (DAT) would let ordinary consumers record high-quality sound. The format was expensive and never caught on in the mass market, but it led to other digital audio formats. In retrospect, we’re lucky to have reached a state where we can record sound without mandatory DRM. (If you don’t believe me, recall that strong encryption was once outlawed.) The article mentions that “Computer manufacturers successfully lobbied to exempt CD-ROM drives from copyright protection technology.” Our technology would be much less advanced today if we had to jump through copy-protection hoops every time we used a computer.
Posted in commentary
Tagged audio, DAT, DRM
Files that Last: Digital Preservation for Everygeek has been out for quite a few years. While the relevant technology has changed in many ways, especially with the explosive growth in cloud storage, I think most of its advice is still useful. I’ve permanently dropped its price to $1.99, no discount code required. The price drop is immediate on Smashwords. It may take longer to percolate to other sources supplied by Smashwords.
PDF is a very popular format. It’s also a hideously complicated one and keeps getting more complicated. It shouldn’t surprise anyone that it has security issues. I just came upon Processing Dangerous Paths — On Security and Privacy of the Portable Document Format, which enumerates many of these risks (and is ironically posted as a PDF). It’s worth a read. Thanks to Johan van der Knijff for mentioning it on Twitter.
The PDF Association has an analysis of the file which the New York Post has uploaded to Scribd, which purports to show a message from Vadim Pozharskyi to Hunter Biden and Devon Archer. Discussions of what it signifies politically and whether Twitter was justified in blocking the link are for another place. The issue in this blog is what the file says about the authenticity of the email. The answer is: Nothing at all.
Posted in commentary
Tagged email, PDF
The more complex a format is, the less chance there is that its security features will work in all cases. A vulnerability has turned up that lets sneaky people alter digitally signed PDF documents. A German team discovered a “shadow attack” vulnerability in the format. It’s easiest to do this if the document’s creator designed it to be altered after signing. The victim sees one set of content and signs it; the dishonest creator gets the document back, changes its appearance, and passes it on.
Posted in News
Tagged PDF, security
When a device uses a relatively obscure image format and a site that accepts uploads fumbles it, who is to blame? This is the question that came up when students couldn’t complete their AP college exams because of such a situation.
Students took pictures with their iOS devices of materials they submitted for the test. Their phones stored and uploaded the pictures in HEIC format. The College Board’s server didn’t recognize the format and timed out. The students immediately failed and were told they could retake the test in three weeks.
Continuing from the theme of my last post, I’ve created a page for learning about file formats. I don’t know much about educational theory, but I’ve picked out links to articles and videos which I consider suitable for high school students starting out to learn about formats. With so many people figuring out how to educate their kids without classrooms, creating resources is one thing I can do. If you think the page is useful, please link to it where the people who can use it will see it.