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Comment by gtsc | Hacker News Reader

Uh, how exactly? The whole point of the private key is that it's only known to MS...

Not every malware, but does, for instance, the NSA run Microsoft signed binaries or are they able to sign their own? If they have valid signing keys, how much can you trust they (and other agencies) will always use those keys for your own good (and that you'll agree it's for your own good) when they use them.

You seem to be new to all this "centralized control" thing... Here's your complimentary link

http://arstechnica.com/security/2012/06/flame-malware-was-si...

Then you can proceed searching for ssl cert fiasco...

It is a fallacy to assume that because private keys have been leaked in the past, private keys will necessarily be leaked in the future.

Remember, the DRM-can-never-work argument doesn't apply here. DRM-can-never-work is that the user must be supplied the decryption key with the encrypted content. That does not apply to signing; you must be supplied the public key, but the private can be held private.

How is that a fallacy? I think the fact that private keys have been leaked in the past demonstrates that they will be leaked in the future.

Do you leave your door unlocked because locks have been demonstrated to be easily broken?

The first rule of security is that security is all about layers.

Also, I sent a copy of your comment to Phil @ Apple, I think he's going to drop all the DRM restrictions on iOS binaries and release Apple's private keys used for signing iOS apps after reading your comment.

Many private keys have remained private. (So far as we know... and note here I'm talking about private as in asymmetric public/private such as can be used for signing, not "keys that were meant to be private but got leaked".)

In fact, I'd observe the Microsoft private key wasn't even leaked. Another private key was created that due to flaws in MD5 allow someone with vast, vast resources to figure out how to forge another one that would be accepted. One can equally read this as proof that the system is pretty strong, if it took government-level resources to attack a known-weak system that I would imagine won't be in the next signing standard.

We can not assume that private keys will leak. We can not even assemble an argument that the probability is high, which is because it isn't.

> it took government-level resources

This year. The next year, it will be half as much. In 10 years, a thousandth. Are we willing to expire boot signing keys every couple years? Are we really comfortable only governments have such power because governments can do no wrong?

In the encryption wars it goes the other way. Encrypters get to make decrypters exert exponentially more effort for only polynomially more themselves, and the systems get stronger over time, not weaker. We've long since passed the point where handheld devices like cell phones can use encryption that would take resources in excess of the entire universe for the rest of time at the maximum theoretical computation rate to brute force. We don't always use that, and there may be (and probably are) weaknesses that can cut that down, but that's the direction this goes in over time, and I can't think of anything that has any chance of changing that dynamic. Even a proof of NP = P wouldn't do it (that only potentially nails certain forms of encryption used today, there are others that would still not be vulnerable), and if that's not enough....

I know all that, but you have to agree UEFI makes everybody put a lot of trust on a series of black boxes we cannot inspect. Even if we assume getting a set of signing keys requires more computing power than physically available, we cannot rely on it not being available through less compute-intensive ways.

Actually, it only demonstrate it's possible for them to be leaked. This is a rather obvious conclusion.

However, if the signing keys remain valid forever and signed binaries don't have to be re-signed when keys expire, you have essentially an infinite amount of time to leak (or crack) the signing keys and the likelihood of a leak will approach 1.

I am much more concerned by the increase in computing power than with leaks. The value of a valid signing key in a UEFI secure-boot world is high enough to ensure someone somewhere will spend inordinate amounts of money and/or computing resources to obtain a valid key. How much does leaking a key cost?

I think you need to be more careful with that argument. While I agree in principle that this sort of flaw is inevitable in the future, and puts a hard cap on the value of measures like secure boot (and I'd go even further and argue that it makes the costs of secure boot higher than the benefit), it's not correct that the signature process is inherently compromised. Public key encryption works, and it works very well. There have been a handful of goofs, and there will be more in the future. But the number of key regimes that attackers would want to compromise (consider even banal stuff like the signing keys for console games, which remain secure after many years) vastly (vastly!) outnumber the few exploits.

Okay, where are the private keys for Apple's iOS signing key, Motorola bootloader for the Droid phone, XBox360 bootloader signing key etc. etc.?

Are they imminently going to be released? While there are definitely flaws in implementations and leaks, assuming them to be foregone conclusions is a mistake.

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