Because, eventually, they'll leak. Security and intelligence agencies have lost keys and hacking tools and top security documents.
And when they leak, the surface for what you can exfiltrate before the keys are rolled over will be _everything_. If you can roll over the key.
Microsoft leaked their Secure Boot key once, and it wasn't possible for them to fix that on all of their devices. Whilst that isn't a particularly concerning leak, that changes if what it was protecting becomes someone's personal information.
To protect against a leak that compromises everyone, everywhere, you'd want the government keys to be unique per site and company. Which would also incidentally make securing those keys harder and lead to more leaks.
And that's before you question whether the people with access to the keys are actually trustworthy and won't do what law enforcement have done in the past, like stalk their ex.
It's a no-win situation.
All of them will leak? Seems like if each key is in possession of a different party, and you need all keys to decrypt, and at least a few are air-gapped only available for warrant holders via manual retrieval... the probability would be vanishingly small.
I agree it's impossible in theory, but in reality nobody has put out significant resources and made an honest effort to try, imo.
I bet I could come up with an encryption scheme that allows decryption for warrant holders only, but the scheme to decrypt will be very onerous for the warrant holder and will require manual retrieval of air-gapped asymmetric keys and lengthy background checks to establish trust (i.e. is this person who they say they are and did the judge really grant a warrant, etc.).
There are always tons of assumptions we make when we say these things.
We assume that the computer used to generate the keys was never connected to the internet, has not already been compromised at the time of key (re)generation, there are no backups of the computer, the engineer that performs the key generation is extremely trustworthy, the room this is done in is perfectly isolated from surveillance, etc. If you start calculating these probabilities and multiply them together, you start observing them moving further and further from 100%.
> but in reality nobody has put out significant resources and made an honest effort to try
These just seem like No True Scotsman fallacies. If anyone comes up with evidence of an effort, are you going to move your goalposts?
IMHO, the incentives don't exist. Law enforcement can't even secure their own technology and vendors (eg. BlueLeaks, OPM hack). The tech companies tasked with this project only see it as a cost center and see it as a potential massive risk to their brand if this system is misused. During the Snowden leaks, there were accusations of NSA contractors using the search system to spy on family members, dating partners, etc.
Human behavior is too predictable to naïvely assume that we can increase security while increasing the number of keys/people who have access to a massive tranche of data.
The nature of the federal executive is a problem here: keys spread among federal agencies are functionally in the hands of one party.
But I agree, it's a perfect example of why we can't trust even the most security-trusted people in the US government with skeleton keys to all of our data.
You can add whatever extra bureaucratic processes you want, but you're still making my encrypted data less secure.
You say that like there isn't form. The keys used by every DRM scheme has leaked. Every one. It was not from lack of trying, not because they didn't have access to the best and the brightest. HDMI was actually pretty good.
The problem is not just technology. It's also humans. Create a big enough prize for obtaining a single thing, and it will leak. Every man has his price.
When the prize is the ability to read every communication of every USA citizen, politician and corporation, if you aren't thinking about what sort resources nations like China and Russia can throw it at, you aren't thinking hard enough.
Whilst in theory ideas like these work, they don't in practice.
When security is tightened, and oversight is made more difficult, we regularly see the players involved skirting the system because they're human and don't think that they're really doing anything wrong.
Stuxnet was a while ago, but pierced an air-gapped network through a means that... Shouldn't have been possible. It was possible because of the failure of the humans involved. A factor that can't be removed.
You would find keys being surreptitiously shared over insecure shares, and getting caught up in other data leaks. Two or more departments sharing keys between employees to save some time and effort. Or forgetting to shred a key securely once it has been accessed. It doesn't take long until everyone in the department ends up with a key - and then each of those is a weak point.
The NSA has had repeated problems with their processes being avoided and ignored by employees skirting oversight to stalk their ex's, by doing things like listening to their phone calls - which supposedly required a warrant. [0]
You can't trust the people involved.
Now, there's a very, very simple way to avoid all of these problems. Secure the data to the fewest number of people required. Placing the responsibility of keeping the keys secure with the direct stakeholders.
An end-to-end encrypted chat still has the possibility of keys being leaked. But only the people who will be directly impacted are involved. You don't need a large and complicated scheme, and it is dead simple to implement, comparatively. You only have to trust the people involved, not swathes of departments.
A far simpler solution to this problem would be to change the law to mandate disclosure of encryption keys / passwords if served with a warrant. I don't agree with this either, but at least it's more elegant than what is being proposed.
Could you argue the stress of going through the legal system made you forget your twenty word password?
Not "if", "when". It will happen, and as soon as it does, everyone's privacy (for previously encrypted content) is gone forever. It is impossible for me (and I think a lot of other people) to imagine the government can keep those keys secret for a reasonable period of time, nonetheless forever.
• https://en.wikipedia.org/wiki/Shamir%27s_Secret_Sharing
• https://cs.jhu.edu/~sdoshi/crypto/papers/shamirturing.pdf
I agree with the sibling commentators though that it just isn't strong enough to withstand a threat model of "people motivated to get the master key to vast amounts of encrypted communication". Even if such a scheme couldn't be cracked algorithmically, it wouldn't hold up against the relentless social engineering efforts that would be thrown at it.
Or, more likely, people charged with protecting the master key being negligent.
One of potentially many examples: https://www.renderlab.net/advisories/mta-key/
For instance, with functional encryption, you are able to distribute or derive keys that have a very specific functional purpose and leaks no other information. Basically it allows you to derive a "function key" that basically computes f(x) for you given an encryption of x. As long as the crypto is strong, no other information about x is exposed (only info about f(x) is revealed).
With the right system architecture, this would allow the government to perform a very specific, pre-defined query to check for illegal content without exposing any additional information about the encrypted data.
Another approach you could use is based on zero-knowledge proofs and verifiable computation. Essentially a government could come along and ask you to provide a proof that your encrypted data does not contain malicious content. Given a program that can check for what they are looking for, you can provide them a zero-knowledge proof that convinces them that you correctly ran their provided algorithm on the suspect data and that the algorithm did not identify any malicious content. In this process, no other bits of information are exposed or handed to the government other than the data is not malicious.
Scheme: multiple copies of symmetric key followed by symmetrically encrypted body (pgp-style). One copy of the symmetric key is secured by user's private key, another is wrapped in an onion of all required "side" keys.
The issue is that the government-held keys only need to be exposed once, and then someone has a key to all of everything, everywhere.
The US government couldn't even keep the most sensitive information about its personnel secret, see the OPM breach: https://en.wikipedia.org/wiki/Office_of_Personnel_Management... The Inspector General had warned Congress of "persistent deficiencies in OPM's information system security program" and nothing was done. This resulted in some really sensitive data being exfiltrated, probably some good blackmail info. The US government has not done a great job even protecting its own employees.
The biggest problem here, though, is incentives. A government cannot be sued, or suffer any other negative impact, if it accidentally loses keys that lead to others' death, blackmail, or job loss. Too bad, so sad. If tomorrow it becomes illegal or unacceptable to do something that today is legal, a government can retroactively punish those who engaged in it. In short, the government has no strong incentive to protect the keys, only you do.
It's easy to enable a third party to read encrypted data, simply give them the key. That is not and never has been the problem.
The problem is ensuring that only authorized uses occur. There is no algorithm that can determine good guys from bad guys. Keys are notoriously hard to keep secret. Any mechanism that tries to transmit them now adds a third party, and we have enough problems trying to keep things secure when they're only two parties. Storing them securely is highly improbable to occur in practice. We cannot even store simple data securely. The OMB breach showed that employees were unwilling to apply basic security practices to protect data about themselves... why would they securely store data when they won't be hurt? Splitting them helps a little, but it doesn't solve the fundamental problem.
And this ignores the fundamental problem that groups like terrorists can simply use a different algorithm. When somebody says please think of the terrorist children, they assume that somehow they will use the bad encryption everyone else is stuck with. If someone is willing to violate one law, they will be willing to violate another.
I am not sure how you got this from conversation above. Still sounds impossible to me.
Problem as stated is, that if skeleton keys are broken, then everything everywhere gets broken.
The fact that government has bad initiatives to keep keys secret, just means it will be easier for bad actors to steal them. But that is just a side argument.
When discussing encryption, many people say that this is an impossible problem to solve because of math. This conversation has shifted to being a problem about incentives. Math is impossible to change. Incentives are changeable. If the only problems here are the specifics of the scheme and the incentives of people involved, those are solvable.
>Problem as stated is, that if skeleton keys are broken, then everything everywhere gets broken.
Which is why you build redundancy into the system that would require multiple independent breaches and a system to reencrypt data in the event of a breach.
It's still a math problem in the end.
Today if you want to break into someones encrypted data, you either have to break encryption algorithm (which is hard and by hard I mean even stuff we consider insecure like 3ple DES are still not broken) or you have to break each data individually.
With skeleton keys that changes. Suddenly all the world secrets are one* key away. That is the big difference. Doesn't matter how you do it, it fundamentally changes the equation
And you open up HUGE attack vector, by enabling bad actors to bribe/coerce people with access to skeleton keys.
* Doesn't matter if you split it up, have different org have parts of keys etc.
During usage, all pieces of master key will have to be brought together into one place (phisical or virtual), so eventually still only one breach is needed.
If I encypt data using encryption without backdoor, then to illegitimately get clear text requires effort X, and it gives access to 1 persons data. If whole country encrypts data using backdoored scheme, then effort Y will give access to data of 100 000 000 people. It would seem that security of the backdoor should be 100mil times stronger then that of usual crypto.
By allowing anyone to encrypt a file to the government's private key, you're vastly increasing the chances that one of these attacks goes from infeasable to easily doable.
Right now, if someone were to find a chosen plaintext attack on AES, they could find someone who will encrypt things with their key, get them to encrypt the chosen plaintext, and then break other things that person had encrypted.
If we used the proposed system, then the chosen plaintext attack would allow me to encrypt the plaintext on my own, and then use it to break everything in the world that was encrypted.
It maybe be technically possible to make such a scheme, but due to the unitary executive, keys split among N government agencies have the same essential practical security as 1 key held by one counterparty, and one counterparty that has no particular interest in the security of your data. So this fails the “preserves security” aspect for the same reason that any system that enables government access must.
Of course the data would still be hackable if a bad actor were to get their hands on both of those keys, but security could be increased by, for example, increasing the number of parties needed to authorize the access.
(Please don't critique the ethical premise here - I make no claim that this is the "right" thing to do, just that it could be plausible)