Did NSA Put a Secret Backdoor in New Encryption Standard? (2007)
schneier.com
schneier.com
About 15 years later, differential cryptoanalysis was publicly discovered. The original S-box values would have been very vulnerable to the attack, but the ones the NSA used were resistant, suggesting that NSA knew about differential cryptoanalysis way ahead of time and were suggesting ways to protect the public against its eventual discovery.
It is possible that there is still some magic in there to let the NSA magically defeat DES, but we still haven't found it. Similarly, it's possible that this random number generator exists for some nefarious purpose, but we have no evidence for it.
Also, this article is 5 years old (the headline didn't say so when I first read this). Schneier was in pretty big self-promotion mode at that time.
I've read an explanation that the USA's focus on security has changed in the days since 9/11/2001. At one time, the philosophy was that the country was more secure when we could all be assured that the privacy of our communications was intact.
But in the last decade we've changed that philosophy. The government's security philosophy now is that the most important thing is for the government to be able to tell what's going on.
So it may be that the parent post's anecdote is quite correct, and reflects the policy of that time. But in the days of the War On Terror, we can't trust that anymore.
(And OT, I believe it reflects a fundamental change in the philosophy of governance that is against the founding principles of the country, and a pretty bad thing. I believe that our strength derives from ... us -- we the people. And so strengthening the government by weakening us in fact weakens the nation.)
EDIT: fix date. Thanks, Retric.
That's never really been the view of the U.S. government. It's always been the view that you should be able to have communications with your neighbor that are secure from everyone except the US government, who obviously need to snoop in order to protect us all.
The security agencies and the police agencies have always pushed for more comprehensive and more invasive surveillance. We've had wiretapping for as long as we've had wires to tap. We crippled Internet security for years. I remember the days of separate US and international Netscape releases, due to crypto export restrictions. It wasn't until 2000 that the restrictions were truly relaxed.
If you need an example, pick the Clipper chip - and even that doesn't _quite_ work out, given how publically that proposal was shot down.
If they had been given that authority things may have been different.
Lets look at the case where X is regulate the sale of switchblades. The federal government has the authority to regulate the sale (commerce) of switchblade knives between states, the federal government does not have the authority to regulate the sale of a switchblade within a state.
Let's look at the case of guns. Do you really think that Montana could say "you can sell Montana-made machineguns in Montan without satisfying federal law"? (The feds don't much care about switchblades. They care about guns.)
See http://en.wikipedia.org/wiki/Wickard_v._Filburn . In that case, the feds got to regulate even though the wheat in question wasn't sold and never left the farm.
Wickard was 70 years ago, interstate commerce doctrine has evolved a lot in the intervening years. In fact I'm a little surprised that you used it as an example. It has been a while since ConLaw I, but I think Wickard is often used as an example of the height of the broad interpretation of the commerce clause. Are you arguing that there is no limit on the power of the the commerce clause? Or that Wickard is the controlling case? Lopez is one of many cases since Wickard where the Supremes walked back such a broad interpretation of the commerce clause.
When prohibition was passed, the Civil War was still in memory and Congress felt it needed a constitutional amendment to ban ethyl alcohol.
Today, if Congress wants to ban a thing they simply pass a law that puts you in jail for its sale or possession. Simple as that.
Today? They have always done that. Which is why the USC reads as follows:
"Whoever knowingly introduces, or manufactures for introduction, into interstate commerce, or transports or distributes in interstate commerce, any switchblade knife, shall be fined not more than $2,000 or imprisoned not more than five years, or both."
The Supremes haven't overturned Wickard.
Yes, they did decide that the first version of the Gun Free School Zones Act didn't have a commerce nexus, but they seem quite content with the current version, which affects only those guns that have gone interstate.
However, the relevant question is whether the Supremes have ever decided that something sold can be exempt from the federal power to regulate interstate commerce.
Take machine guns. A Montana statute that allows unrestricted sale of machine guns made in Montana clearly affects "commerce" (in Montana at the very least) of guns not made in Montana, aka "interstate guns".
Do you really think that the Supremes would reject that argument? On what basis?
And, if they accept that argument wrt guns, why wouldn't they accept it wrt cantalope?
The United States Constitution is the highest law, and provides for different treatment of foreign and domestic matters, so your statement is obviously false even under the most broad interpretation of "the government".
The President/Executive (closest to what many other countries would consider "the government") is also limited in most matters by the laws passed by Congress, so even assuming domestic regulation of cryptography were Constitutional (and I don't personally believe it would be), if Congress has not passed a law giving the Executive the authority to regulate it, the Executive cannot do so.
The suggestion that policy is justified merely because it subsists upon formal authority is nonsense.
https://en.wikipedia.org/wiki/Thomas_Andrews_Drake#2007_FBI_...
https://en.wikipedia.org/wiki/NSA_warrantless_surveillance_c...
The thing is that they can not bring the result of this warrantless wiretapping into court. But they probably don't want to.
From what I've seen the FBI is a lot more vocal in complaining about the impact of encryption because their mandate involves bringing cases to court so they want a formalized, legitimate way of breaking encryption when they have warrants. They would also love to have the dragnet that the NSA has to know who to watch, and I don't know to what extent they do, but the bigger difference that I see is that the NSA is not interested in launching court battles (any more) whereas that is the primary endgame for the FBI.
The problem of course is that an encryption system which can be broken in a formalized way is open to the possibility of being broken by the wrong people. You can't have your cake and eat it too by having strong encryption that can be broken by the "right" people because there is no way to theoretically describe who the "right" people are. The encryption has to work the same for everyone.
Like all big issues in society there are competing rights; the need for law enforcement bumps up against the freedom of the individual. I believe that we are comfortable enough pushing this balance more heavily towards the freedom of the individual in America that a policy of embracing strong encryption is in the best interests of everyone, but I am aware that I don't have as much knowledge about this issue as some others.
Doing this in a non-obvious way seems much more difficult, but if the NSA did have a weakness to DES, it could very possibly require knowing a secret key.
There is simply nothing to this analysis. The crypto policy fight happened in the late '90s, and crypto won.
It should be clear from recent controversies about "how private is your cellphone"; warrantless wiretapping and retro-active legalization of the same; various proposals for granting government authorities over the Internet (including a "kill switch" and a rumored upcoming Executive Order since he can't get it through Congress); that in the broader context, the US government is very much interested in monitoring communications.
You have a lot more to fear from the Linux devs "cleaning up" OpenSSL's CSPRNG than you do from the NSA.
This was back in the late 1990s and there was a lot of discussion on the cryptography usenet group at the time (i.e. http://www.mail-archive.com/cryptography@metzdowd.com/msg007...) but there is a fairly readable mass market piece here (http://scard.org/gsm/pr/nytimes/). I'm only an amateur when it comes to this stuff, but why do you think David Wagner is wrong?
1. Most people are unable to do this technically.
2. The fact that you do it may constitute prima facie evidence of being a person of interest.
3. The government is trying very hard to get the means to wiretap VoIP.
4. It doesn't address traffic analysis at all. I know you said you aren't concerned about this, but there are plenty of people who are, and the government is going like gangbusters (literally, I guess) toward this.
The US Government hasn't restricted traffic analysis, and indeed nothing they have ever proposed W.R.T. encryption could have controlled traffic analysis.
As to pure software crypto it's not really that important vs securing the endpoints. Consider WoW uses encryption when logging in, but a significant % of accounts are hacked before they add an authentication either as a key-chain or on your cellphone. I suspect if it ever became mainstream pure client side bitcoins would be DOA for more or less the same reasons.
"We've captured a bunch of data. But as long as we don't observe it, it's not legally going to be counted as intercepted."
Sounds to me, like a massive slippery slope just waiting to happen.
That was the talk at Defcon, I didn't do enough follow up to find out but it's pretty open that the new Utah data center can store every American's phone calls, emails, .. everything for a century.
If you can slip that through whoever it is that protects us, there are some corner cases. Say we do rub out a terrorist cell that does a successful attack (20 years after this database is running,) could you then mine that database to determine if your AI that finds terrorists works? If I was training up voice finger printing algorithms and such, you have an incredible dataset and there are likely other signals coming in to help populate it (maybe the census? say you're training something that detects Arab accents)
Never mind the fact that it's so huge and so much data that 1) is has to be online and 2) all intelligent queries will be given to AI/Google like software agents to find. Could a future president query the database to dig up dirt on an upcoming election opponent? (He's the president right?)
;)
The NSA may also have know who else knew about differential cryptoanalysis, and didn't want it to be weak in ways that others could break it, but left it weak in ways that they could.
They're only just released some of the stuff that Turing did.
They keep things secret, and they use things hard. There's not really anyway to know what they know about your system, which is why cryptography likes systems that seem secure even when you know everything about that system.
So imagine what they do with the secrets that are still secret - the secrets not independently developed and made public.
So either the public is doing a decent job of keeping up with the spooks, there's a massive misinformation campaign where intelligence agencies only admit to having discovered things that the public discovered soon afterwards, or there's a strange bimodal property where the public replicates private results either five years later or fifty.
Also, the NSA is not _fundamentally smarter_ than the rest of the world; they're just possibly more focused on it. So exactly how a clever idea would occur to them in the 1970s and 1980 and have occurred to nobody in academia since then needs some explanation.
"In 1994, a member of the original IBM DES team, Don Coppersmith, published a paper stating that differential cryptanalysis was known to IBM as early as 1974, and that defending against differential cryptanalysis had been a design goal."
58 50 42 34 26 18 10 2
60 52 44 36 28 20 12 4
62 54 46 38 30 22 14 6
64 56 48 40 32 24 16 8
57 49 41 33 25 17 9 1
59 51 43 35 27 19 11 3
61 53 45 37 29 21 13 5
63 55 47 39 31 23 15 7
At the time, it was totally unclear why you had rearrange the bits in this very exact way. After all, you were about to encrypt it (and obliterate any plaintext patterns) anyway. And would it be as strong if you started with the 57th bit, instead of the 58th? The whole thing seemed so arbitrary.
Now it's true that this is robust to differential cryptanalysis, but it's also true that these bit permutations significantly slow down software implentations of DES. But it's trivial to implement the initial permutation in hardware.
In the 1970s, the hardware required to crack DES costed $20,000,000 US dollars [1] (about $120 million in today's dollar [2]). The general tinfoil-theory at the time was that 1) only the NSA had the resources to build such a machine and 2) by forcing DES to use this initial permutation, the NSA was giving themselves a significant "head-start" over everybody else using software to crack DES.
[1]http://www.krapp.org/hydra/courses/analysis/3-DataEn.pdf (PDF) [2]http://www.wolframalpha.com/input/?i=%2420%2C000%2C000+1970+...
What was altered were the 8 S-boxes, seemingly random lookup tables that map 6- to 4-bit values. More details by Don Coppersmith himself at: http://simson.net/ref/1994/coppersmith94.pdf
You do not need to be on guard against secret NSA Dual EC backdoors.
Actually the NSA s-boxes are weak against linear crypto analysis. http://reference.kfupm.edu.sa/content/l/i/linear_cryptanalys...
If I remember Schneider's applied cryptography correctly, the NSA s-boxes were among the worst 7% possible.
I wonder what we would be saying about the NSA if we (publicly) discovered linear crypto-analysys before differential. However, I suspect the vulnerabilty to linear analysys is the result of how structured they made it to resist differential.
IIRC, during the standarization of DES, the NSA has also modified some S-Boxes without giving any explanation. Only later, when differential cryptoanalysis became known to the public, it was clear that this was to strengthen DES against this particular attack (which was already known to the NSA).
The case here is more interesting though: It seems like you need to know some secret numbers (a sort of "private key" if you will) to be able to attack the PRNG. So it seems that the NSA could place a "safe" backdoor that even an attacker with the same cryptography knowledge as they have cannot break unless he himself possesses the "private key".
It was an interesting story because it was so weird. But even had Dual EC not become known to the world exclusively as "the CSPRNG with the backdoor in it", nobody would have used it anyways.
Most people learn much better by doing (or getting done).
I don't have any evidence for that, just speculation on one reason the NSA might insist on including something like this in the spec.
Not happening. Hasn't yet, nor will it. NSA just keeps quite and watches for someone to use their particular algorithm. We should assume malicious intent and take Schneier's advice: "My recommendation, if you're in need of a random-number generator, is not to use Dual_EC_DRBG under any circumstances."
And if you "don't have anything to hide," then I propose you've given up already and cryptography is useless to you.
Good, modern cryptography offers a level of security unparalleled in the physical world, and at a processing cost which any computer can handle. Why would you intentionally choose something inferior?
You can never be infinitely certain, but nor can you be certain your non-backdoored crypto is secure. There are cases where "the NSA leaks their top-secret backdoor to the internet" is a vanishingly small threat vector compared to other possibilities (e.g. rubber hoses).
>Good, modern cryptography offers a level of security unparalleled in the physical world, and at a processing cost which any computer can handle. Why would you intentionally choose something inferior?
You wouldn't. But if it later turns out the NSA has a backdoor in the algorithm you happened to pick, and for whatever reason you're unable or unwilling to change algorithms now, that still doesn't mean "you've given up already and cryptography is useless to you".
True. But "is this algorithm crackable?" is a question that can be answered with experimentation and math. "Has the NSA lost its keys or its scruples, and if not, will they ever?" cannot be answered at all until you know you've been hacked.
> But if it later turns out the NSA has a backdoor in the algorithm you happened to pick, and for whatever reason you're unable or unwilling to change algorithms now, that still doesn't mean "you've given up already and cryptography is useless to you".
Maybe not, but it does mean you value something else more than you value security. Yes, everyone makes cost/benefit decisions about security. But if your answer to "whoops, whoever knows this trick can see all our bank transactions" is "meh, it would take like, a week to fix that," you're placing a pretty low value on security.
This is, obviously, a really old example, because modern hardware makes encrypting things quick and easy, and decrypting things quick and easy. But imagine strong encryption in the 1980s - you had to balance strength with time with size and then try to cram it into low-specced hardware.
My point was that there's no point in picking something with a known back door when there are perfectly good, non-compromised alternatives.
RC4 actually has a huge internal state. You could use a 1600 bit key with it if you wanted to.
2 - A nightmare to implement securely
3 - Only exists for the sake of provable security
4 - The same standard defines a much better alternative pseudorandom generators based on hashes and/or block ciphers.
Overall, the mental game is quite taxing, so I'm going to plead "bureaucracy."