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Encryption Security

'Logjam' Vulnerability Threatens Encrypted Connections 71

An anonymous reader writes: A team of security researchers has revealed a new encryption vulnerability called 'Logjam,' which is the result of a flaw in the TLS protocol used to create encrypted connections. It affects servers supporting the Diffie-Hellman key exchange, and it's caused by export restrictions mandated by the U.S. government during the Clinton administration. "Attackers with the ability to monitor the connection between an end user and a Diffie-Hellman-enabled server that supports the export cipher can inject a special payload into the traffic that downgrades encrypted connections to use extremely weak 512-bit key material. Using precomputed data prepared ahead of time, the attackers can then deduce the encryption key negotiated between the two parties."

Internet Explorer is the only browser yet updated to block such an attack — patches for Chrome, Firefox, and Safari are expected soon. The researchers add, "Breaking the single, most common 1024-bit prime used by web servers would allow passive eavesdropping on connections to 18% of the Top 1 Million HTTPS domains. A second prime would allow passive decryption of connections to 66% of VPN servers and 26% of SSH servers. A close reading of published NSA leaks shows that the agency's attacks on VPNs are consistent with having achieved such a break." Here is their full technical report (PDF).
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'Logjam' Vulnerability Threatens Encrypted Connections

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  • Really? The online JS test tells me my Iceweasel 38.0.1 isn't vulnerable.

    "Good News! Your browser is safe against the Logjam attack. "

  • by xxxJonBoyxxx ( 565205 ) on Wednesday May 20, 2015 @09:16AM (#49734973)

    From TFA: "Generating primes with special properties can be computationally burdensome, so many implementations use fixed or standardized Diffie-Hellman parameters. "


    • The root cause is people shouting "Don't roll your own crypto!" and scaring people away from using anything but the bog-standard, NSA-approved shit.

      • by HiThere ( 15173 )

        OTOH, using "roll your own crypto" is nortorious for individualized holes and weaknesses. It does tend to mean that the "one size fits all" means of breaking the code won't work, however. Or at least may well not work.

        That said, if you have good enough communication to share custom crypto programs, you may be better off using a one-time that can't even theoretically be broken. But it does require a good source of random numbers (e.g. amplified triode vacum tube with no input so you're just amp

        • by thogard ( 43403 )

          There are things that can be done and things that shouldn't. For example there is a byte table of sines in MD5 that help scramble bits. If you scramble that table at all then you have a hash that is as strong as MD5 but unique as if someone tacks on a 2^2048 extra seed. It also keeps off the shelf hardware from trying your hash.

          If you do the same thing with the DES S-boxes you can end up with a cryto that is so weak you might be able to decrypt it by inspection.

      • by suutar ( 1860506 )

        if they can't understand the difference between writing their own code and generating their own random numbers they're better off doing neither.

    • It takes my (2009 era) machine 5-300 minutes (it varies wildly depending on how lucky you get) to generate a set of 4096-bit DH parameters. And that's actual CPU time, not "sitting around waiting for the Linux entropy pool to regenerate" time. You're going to have to make some tradeoffs here.

  • by gweihir ( 88907 ) on Wednesday May 20, 2015 @09:39AM (#49735093)

    At the time these utterly stupid laws were made, these ciphers where still somewhat secure against most attackers. The problem is that encryption software and parameters can stay in use for a long time.

    • Yet Australia wants to return to "export-grade" encryption [].

      • by gweihir ( 88907 )

        The Australians will either come to their senses of find themselves squarely in the second world in the long run. Some researchers already left the country and a lot more will be thinking about it. It will be interesting to see what will happen.

        However, if recent history is any indication, Australians like to get screwed over by their government, hence they keep voting for anti-citizen politicians. Must be some kind of collective masochism going on down under.

        • by _merlin ( 160982 )

          However, if recent history is any indication, Australians like to get screwed over by their government, hence they keep voting for anti-citizen politicians. Must be some kind of collective masochism going on down under.

          All our major political parties (Liberal/National, Labor and Green) have anti-citizen policies. Much like the US Republicrat system, while you can choose who's going to be fucking you, you'll still have to bend over.

  • Did this flaw come into existance due to lazy programmers trying to save run time, or did the NSA install this as a back door? How badly has the NSA sabotauged the border defences of the USA?
  • by Anonymous Coward


  • by nimbius ( 983462 ) on Wednesday May 20, 2015 @09:54AM (#49735197) Homepage

    caused by export restrictions mandated by the U.S. government during the Clinton administration.

    So this assertion arrives at one of two uncomfortable conclusions.
    1. US intelligence agencies have had the ability to exploit this for more than a decade
    2. US intelligence agencies, having understood advances in computing to be inevitable, carved a backdoor and did some wishful thinking.

    Either way the internet is starting to realize not all well-intentioned backward compatibility that also includes an unfortunate downgrade in security is done in altruistic or neutral capacity. Shell companies and paid researchers can and have in the past intentionally rendered well constructed algorythms and crypto effectively optional in the name of compatibility and their product. Ephemeral ECC for example, although cited by reseachers as a means to avoid this kind of attack, is suspect. The NIST elliptic curves have now been tainted by Snowdens revelations as well. the SSH 2 implementation of the 25519 curve, by Aris of the libssh project, attempts to address the problem of divergences in elliptic-curve cryptography by proposing a safer alternative that doesnâ(TM)t implement the mysterious constants common among other schemes.

    • by Creepy ( 93888 ) on Wednesday May 20, 2015 @10:20AM (#49735357) Journal

      It actually has more to do with export law - in fact, Clinton's Executive Order transferred control of encryption from the Munition List to the Commerce Control List. Prior to the Clinton updates, the maximum exportable encryption was 40 bits. Part of the reason the change got Clinton's attention is the PGP investigation [], where the creator of PGP exported the computer code in a hardback book (free speech) as opposed to in a computer (munitions), allowing it to be scanned and compiled outside of the US. Also the weak foreign encryption export limits were starting to hurt US businesses (mine included at the time - we outsourced all encryption work and worldwide distribution to England, leading to about 20 US workers losing their jobs).

  • The name of the article is virtually incomprehensible due to this shit. How about the original idea about saying a new TLS vulnerability? Would it be so fucking difficult? Yeah, mod me down.
  • ... and here's the breakdown:

    IE and Safari test OK.

    Firefox, Chrome, and Opera fail the test.


    That's on my HP desktop at home.

  • Don Draper is busy writing copy for these vulnerabilities. Seriously, why are pathetic neckbeards the world over so obsessed with making these cute vulnerability names and logos? Since when did a security vulnerability need branding? I guess a CVE ID is unwieldly but when will the madness end? Is the next one going to be called FailPwn1012?
    • by Zaurus ( 674150 )
      Worse than branding...there doesn't seem to be a CVE assigned to this at all. Has anyone found one?
  • How long before legislators and the White House understand that this kind of restrictive export law simply handicaps US researchers and corporations? Competitors from other nations such as India and Russia get a significant advantage over their opposite numbers in the, er, Land of the Free.

  • Logjammin (Score:4, Funny)

    by captjc ( 453680 ) on Wednesday May 20, 2015 @11:52AM (#49736249)

    "Hello, meine dispatcher says there eez somezing wrong mit deine Encrypted Connections?"

    "Yeah, come on in. I'm not really sure exactly what's really wrong with the cable."

    "That's why they sent me, I am an expert."

  • Emilia from the OpenSSL team just published a good blog post that explains some of the "twists" of logjam, and also what OpenSSL is doing about it. It's here: []

  • The Clinton Adminstration couldn't have been responsible for this cause it was Bush's fault.
  • Breaking the single, most common 1024-bit prime used by web servers

    Well that's silly. They should try using different primes for a start.

  • Encryption is a defensive technology, not a weapon.

    I can't see any good reason (plenty of bad ones!) for ever limiting defensive technologies. Weapons are a different matter because they can cause direct harm to others, but a shield, or armour, or encryption, are all defense only with no offensive angle. They should never be limited.

    • Defensive technologies also enable combatants, sometimes more than a particular offensive technology.
      • by green1 ( 322787 )

        But they do far more to protect the innocent than they are capable of doing to assist an enemy.

        As long as governments continue to see innocents as the enemy, we have all lost.

  • by Ungrounded Lightning ( 62228 ) on Wednesday May 20, 2015 @01:39PM (#49737679) Journal

    I skimmed the start of the paper. If I have this right:

      - Essentially all the currently-deployed web servers and modern browsers have the new, much better, encryption.
      - Many current web servers and modern browsers support talking to legacy counterparts that only have the older, "export-grade", crypto, which this attack breaks handily.
      - Such a server/browser pair can be convinced, by a man-in-the-middle who can modify traffic (or perhaps an eavesdropper-in-the-middle who can also inject forged packets) to agree to use the broken crypto - each being fooled into thinking the broken legacy method is the best that's available.
      - When this happens, the browser doesn't mention it - and indicates the connection is secure.

    Then they go on to comment that the characteristics of the NSA programs leaked by Snowden look like the NSA already had the paper's crack, or an equivalent, and have been using it regularly for years.

    But, with a browser and a web server capable of better encryption technologies, forcing them down to export-grade LEAKS INFORMATION TO THEM that they're being monitored.

    So IMHO, rather than JUST disabling the weak crypto, a nice browser feature would be the option for it to pretend it is unpatched and fooled, but put up a BIG, OBVIOUS, indication (like a watermark overlay) that the attack is happening (or it connected to an ancient, vulnerable, server):
      - If only a handful of web sites trip the alarm, either they're using obsolete servers that need upgrading, or their traffic is being monitored by NSA or other spooks.
      - If essentially ALL web sites trip the alarm, the browser user is being monitored by the NSA or other spooks.

    The "tap detector" of fictional spy adventures becomes real, at least against this attack.

    With this feature, a user under surveillance - by his country's spooks or internal security apparatus, other countries' spooks, identity thieves, corporate espionage operations, or what-have-you, could know he's being monitored, keep quiet about it, lie low for a while and/or find other channels for communication, appear to be squeaky-clean, and waste the tapper's time and resources for months.

    Meanwhile, the NSA, or any other spy operation with this capability, would risk exposure to the surveilled time it uses it. A "silent alarm" when this capability is used could do more to rein in improper general surveillance than any amount of legislation and court decisions.

    With open source browsers it should be possible to write a plugin to do this. So we need not wait for the browser maintainers to "fix the problem", and government interference with browser providers will fail. This can be done by ANYBODY with the tech savvy to build such a plugin. (Then, if they distribute it, we get into another spy-vs-spy game of "is this plugin really that function, or a sucker trap that does tapping while it purports to detect tapping?" Oops! The source is open...)

  • NSA owning VPNs is not surprising given pathetic state of VPN technology as currently deployed. Widespread use of group keys, PPTP and challenge response authentication. A tragedy of nonsense NSA would have to be negligently incompetent to not take full advantage of.

    It isn't like this is a big secret or that people don't know better. The bells have been ringing for years ... dare I say decades in some cases yet many in a position to know better simply don't care.

    What is interesting to me distance between

"The algorithm to do that is extremely nasty. You might want to mug someone with it." -- M. Devine, Computer Science 340