Kuhn: At Least Motorola Admits It

"The e-fuse part seems to be pure conjecture based on seeing the name of the technology in M-Shield's key storage (e-fuse), and then thinking it must work like the ones you buy down at Radio Shack, or the thermal fuse you find in an average coffee pot. ie. If you accidentally do something bad with the device, it blows its fuse and refuses to work until the fuse is replaced. The thin description on Wikipedia doesn't help."

Right, but the problem is that we have only conjecture about what parts are true, which parts are false/wrong, and what parts are conjecture. :)

"E-fuses are used more like jumpers of yore (only shrunk to be on the die) than like the ones in your fusebox in the garage. We architect our software and arrange our manufacturing flows accordingly. (Beyond that level of description, I'm not sure where I cross into proprietary information, so I'll stop there.)"

No worries; I respect that (I used to work at a large hard drive manufacturer for two summers). It sounds a lot like this is a plausible scenario.

"The fact that the device is recoverable by a reflash implies that nothing truly permanent has happened to the device."

Well, no. Strictly speaking, Mot says

"If a device attempts to boot with unapproved software, it will go into recovery mode, and can re-boot once approved software is re-installed."

How the re-installation can occur is completely unspecified. It could conceivably be that the OP was correct that the software can fuse a selected part in order to require you to go back to the shop and get a new chip, or get a second fuse blown for you (perhaps something like DVD drives do where you get five free reflashes at the store and then it's clear you're a baddie and you have to buy a new phone (or even just a new chip)) It's hardware/software; the primary constraints are laws, consumer (or customer, if they're like me and know and use the distinction) reaction and how much we can pack into a chip before it's too big/consumes too much power. Hooray for digital progress!

"This mode should be the same mode the phone goes to if a legitimate update fails, say, due to a power glitch during the update." It *could* be the same, but we have only supposition.

"That's got nothing to do with the e-fuse question at hand, though. It just determines how you restore the phone once it's been flashed with unauthorized code."

They might be unrelated. They might not be unrelated. We have no [b]data[/b], we have only supposition (and layer upon layer of it). There are definitely scenarios that could involve the fuse, even if the supposition that the fuse is permanently blown is true.

"Refusing to load unsigned code until a service center reinstalls it isn't nearly so malevolent as irreversibly destroying the phone."

Malevolence is motivation and rather tangential to the questions at hand. Rather, the question is what the [i]problems[/i] to us would be. and how problematic having a phone be a brick until you get it to a service center depends on a lot of things, and notably how far and inconvenient it is to get to the service center. :)

To summarize, my current position is that we need a lot more data before we can draw reliable conclusions about anything in this situation. Hopefully mot will be forthcoming with it. I'm very very glad you brought more data to the table. Despite not necessarily being directly transferable to the mot scenario, they're at least indicative about the state of current technology.

"I told them I didn't want to have to root my phone to be able to use it in the way that I want."

I'll drink to that! (Is incidentally why I don't have an iphone; my mac fanatic friends/colleagues said, well just root it to get an xterm and ssh.. riiiiight. "Jailbreaking" is rather a poor metaphor; rather, it should be something like hostage-freeing perhaps, or something involving a raid on a property theft ring and getting your TV back. :)