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Comment by vidarh | Hacker News Reader

She is talking about the SD cards in her camera, presumably. I don't know if you can get cameras that supports encrypting the images as they're written, but it's not unreasonable that she wouldn't have one, and not unreasonable that she'd be reluctant to trust whether or not formatting/overwriting the SD card would be sufficient to prevent recovery.

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This sounds like a great unmet opportunity to create a camera for journalists that encrypts every picture to a public key that only your editor (presumably in a safe location) has the private key to decrypt.

And instantly uploads it (or at least, as soon as the camera is plugged to a phone).

That part you can handle with a Transcend or Eyefi wifi-enabled SD-card. The Transcend cards have also been thoroughly hacked so they can be fairly easily customized.

Excellent idea. For journalists - or just for citizens who happen to be standing around in the wrong place at the right time.

Some cameras have open-ish firmware so it sounds easy enough to add. Unfortunately, the big SLRs from Canon and Nikon have terrible firmware run by an organization that's stuck in the 80s or worse with the typical poor level of software hardware companies are known for.

Actually Canon makes their SDK freely available and while they don't let you fork the operating system there's an open-source alternative called Magic Lantern that works very well on most of their DSLR range and adds a lot of functionality (as well as providing a lot of reverse engineering info on their hardware through the site). Canon hasn't officially blessed this, but they haven't obstructed them in any way.

The main problem with adding encryption would be that photos and video can consume a lot of bandwidth, and the bandwidth inside a digital camera is limited, as is the processing power. It would make more sense to put the encryption directly on the media card, similar to the fashion in which Eye-fi cards include a tiny CPU and web server to automatically offload the content to a trusted network.

Rather than an entire camera (which would have incredibly high R&D costs and likely not be on the same level as professional cameras), why not just an SD card which encrypts the data before it writes it to flash?

If the SD card stores the encryption key inside itself, how is it even remotely secure?

it would just store the public key only.

Fair point: that should work.

I'm just worried that could confuse the camera, though: image preview wouldn't work, checksumming wouldn't work...

I would envision more of an adapter form factor, where the hardware encryption is done on an SD-card shaped device which has a removable MicroSD slot in it for the actual storage.

That offers only marginal improvement. If you were arrested with your camera, the police would take possession of both the adapter and microSD card, rendering your encryption a mere annoyance (if they even noticed it!)

Presumably you could just write an Android app for that and run it on a Samsung Galaxy NX.

I guess some overwrites should be enough

for i in $(seq 1 1000); do if=/dev/urandom of=/dev/sdc bs=$((1024 * 1024)) count=(SD size in MB); done

Securely erasing flash memory is surprisingly hard.

>Whole-disk wiping techniques faired only slightly better with SSD media. In the most extreme case, one unnamed SSD model still stored 1 percent of its 1 GB of data even after 20 sequential overwrite passes on the entire device.

http://www.theregister.co.uk/2011/02/21/flash_drive_erasing_...

I wonder how hard it is on SD drives.

Meanwhile this forum claims the NSA mandates physical destruction https://discussions.apple.com/docs/DOC-5521

Actually what if one of the blocks used for the critical data was deemed degraded and removed from the pool and replaced with a reserve before it was overwritten. No way to delete then although expensive to retrieve it might be possible.

Depends on the capability of your opponent and the consequences if your guess is wrong.

Yeah, also block size, I'm not sure how big they usually are. 512 bytes should be ok (for a picture), if it's bigger I'd be more worried

Might be easier to microwave the SD card

Flash uses pretty large block sizes (look up specs for write size and erase size for common flash media; it's often 4KB writes+128KB erases), and the wear leveling algorithm can unpredictably shuffle the writes around. Your final paragraph is probably the only safe way to know an SD card's internal flash is unrecoverable, followed by physical destruction.

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