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Comment by WalterBright | Hacker News Reader

> But that is complicated and expensive.

Complicated, maybe, but expensive? Once the software is written, there should be no more cost.

> a powerful magnet

A simpler approach is, before recycling electronics, a couple blows with a hammer on the circuit board ought to take care of it. Sure, a well-funded actor may still be able to retrieve something from the memory, but unless you are a very valuable target, nobody will find it worthwhile to reconstruct a shattered circuit board.

It's why I was always amused by people worrying that an electron microscope could retrieve data from a hard disk drive rewritten 6 times. Yah, nobody's going to do that.

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> Once the software is written, there should be no more cost.

You'd need to include a Secure Enclave chip or something like it in each device. That adds cost. I've worked with IOT hardware vendors before. They will argue with you over 128K of RAM because of the cost. Every extra chip, every ounce of weight hurts their profitability at scale.

> A simpler approach is, before recycling electronics, a couple blows with a hammer on the circuit board ought to take care of it.

But then you can't reuse it. The whole point is to resell it to avoid e-waste.

> It's why I was always amused by people worrying that an electron microscope could retrieve data from a hard disk drive rewritten 6 times. Yah, nobody's going to do that.

The NSA would do that to a recovered Russian or Chinese hard drive.

Recycling is not the same as reselling.

> a recovered Russian or Chinese hard drive

Bit by bit with an operator and an electron microscope, how long will it take to recover a 1 terabyte drive?

An encryption key not stored on a secure enclave would still enable a robust factory reset, no?

It just wouldn't protect against some physical attacks to an unreset device.

Yes, it could be done without a Secure Enclave. In which case the data would be vulnerable in the case of theft or resale without a reset, but would be protected if it were reset, as long as the storage of the old key was actually properly wiped.

The trouble with using a hammer is that you'll need to break the flash chips themselves. Breaking just the board isn't enough if the contents are not encrypted. The chips are easy for an adversary to identify, but difficult for an average consumer.

I have no idea what a magnet is supposed to do to flash chips, though. I thought that only affects magnetic media like hard drives.

People buying your stuff on ebay or from the thrift store are not going to desolder the flash chip and solder it into an identical board.

They'll just move on to an easier target.

It's like locking the door on your house. Sure, someone really wanting to get in will bypass it. Opportunistic criminals, which are the vast majority, will just move on. You just have to not be the slowest guy in the herd running away from the leopard.

> a couple blows with a hammer

First, put it in a heavy-duty freezer ziplock bag and then place on concrete. This allows you to nicely pulverize the chips into many tiny pieces without making a mess. A hammer works well, but a few taps with a sledge hammer is even better and somehow more satisfying.

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