It's not even a "backdoor", it's documented in the datasheet...

http://datasheets.chipdb.org/VIA/Nehemiah/VIA%20C3%20Nehemia... (page 82)

...which along with the already publicly-known microarchitecture of the C3 makes this statement sound like total nonsense:

The rosenbridge backdoor is a small, non-x86 core embedded alongside the main x86 core in the CPU

I remember laughing at this with a few others knowledgeable in x86 when it first came out; a self-proclaimed "security researcher" who somehow failed to RTFM.

There's even a Wikipedia article about it now, with a link to the alternate instruction set documentation: https://en.wikipedia.org/wiki/Alternate_Instruction_Set

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inigyou 2 hours ago | parent | next [-]

Was this documentation public at the time? The pdf still does not document the instructions themselves.

	▲	userbinator an hour ago \| parent \| next [-]
		It was public at least 4 years before he first announced his discovery: https://web.archive.org/web/20140130160743/http://datasheets...
	▲	23455646gg3g an hour ago \| parent \| prev [-]
		yes, AIS was known sandsifter was lots of noisy PR, but no new encoding findings

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phire an hour ago | parent | prev | next [-]

"It's documented in the datasheet" is such a weak excuse for a backdoor.

Documenting a backdoor doesn't make it not a backdoor, just means it's not a hidden backdoor.

The fact that a number of machines shipped with the backdoor accidentally enabled, and nobody noticed for over a decade shows just how dangerous even a documented backdoor can be. The oversight wasn't even detected by someone reading the manual, it was detected by a security researcher who wrote a generic tool to fuzz out such backdoors.

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brador an hour ago | parent [-]

Doesn’t backdoor imply hidden? If it’s clearly documented it’s just a (front)door?

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blank429384jf an hour ago | parent [-]

backdoor means a secondary access point that defeats the security features of the primary. In the door analogy, the home owner spends a ton on a lock and camera for the front door but doesn't even have a deadbolt on the back.

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close04 39 minutes ago | parent [-]

Every definition of a “backdoor” in computing implicitly or explicitly considers it hidden/covert.

In the house analogy you don’t see the backdoor when approaching the front. If it was just “an alternative everyone knows about and can be broken easier than the front door” then it probably would have been called “a window”.

Most login forms have a weaker option like a SMS 2FA or password reset fallback. Nobody calls it a backdoor. It’s just a crappy second front door, or window.

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blank429384jf 20 minutes ago | parent [-]

I'm probably mistaken, but I've always referred to password resets as backdoors. Is there another term they could be classfied as?

	▲	close04 8 minutes ago \| parent [-]
		> Is there another term they could be classfied as? As an advertised feature of the product. Your personal definition doesn’t match the general understanding of the word and concept. By your definition every window on a house or car is a “backdoor”. Anything with an advertised fallback is a backdoor. And sometimes the “front door” is the back door: getting money from an ATM is less secure than with an ID at the bank teller.

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cinntaile 2 hours ago | parent | prev [-]

It's not as clear cut as you describe it here. In the other old thread you linked there was no real consensus if this should be considered a backdoor or not.