On Encryption

Posted on Sep 7, 2013 by coderrr

From all the news, it appears that there is one thing clear: Nobody is certain as to the exact capabilities of the NSA, other than the NSA itself. However, as soon as the limited information was released, we began conducting research and were able to draw some conclusions. As of now, Bruce Schneier appears to be our best source of information in regard to this matter, as he is a security and cryptography expert, and often speaks in the defense of civil liberties. He has been given direct access to Snowden’s source NSA materials.  As such, at this point he is the only one, on our side, that is in a position to make conclusive educated guesses about the NSA.

Dead or Alive
To begin, encryption, in general, is neither dead nor useless. Both Snowden and Schneier have made strong statements indicating as much. “Encryption works. Properly implemented strong crypto systems are one of the few things that you can rely on,” said Snowden. In addition, Schneier said, “I believe this is true.” He continued to say, “Trust the math. Encryption is your friend. Use it well, and do your best to ensure that nothing can compromise it. That’s how you can remain secure even in the face of the NSA.” However, the media seems to be spinning things as if encryption is broken in its entirety. If it is not, then the question remains, what is broken?

Long Live the King
It is to our best understanding that 1024bit RSA must be retired. It is most likely able to be cracked in a much smaller time frame than originally thought possible. There are multiple facts that we’ve observed that led us to this conclusion, with the following quote seemingly confirming our suspicions: “Another program, codenamed Cheesy Name, was aimed at singling out encryption keys, known as ‘certificates’, that might be vulnerable to being cracked by GCHQ supercomputers.” This is indicative of the fact that only certain types of certificates are crackable, and the most likely culprit for that is the weak 1024bit RSA certificate which is still commonly used by many websites. If this is true, then it has huge implications for HTTPS traffic, but has minimal impact on OpenVPN traffic. Due to the fact that most web servers do not use an ephemeral key exchange, the vast majority of HTTPS traffic is decryptable by obtaining or cracking the RSA certificate’s private key.

3 Ghosts of Surveillance
Ephemeral key exchanges differ greatly from that of the non ephemeral key exchanges due to the fact that they do not rely, in any way, on certificates for the exchange of their secret keys. In other words, if a criminal is spying on your encrypted connection, even if the criminal were to somehow obtain the private key of the certificate, he or she would not be able to decrypt the transmission. In contrast, a non ephemeral key exchange relies solely on the secrecy of the certificate’s private key in order to maintain exchange secrecy. As such, in this case, once a private key is compromised, then all past, present and future non ephemeral exchanges will be compromised, just by watching them.

The silver lining to this is that if all web traffic simply upgrades to using ephemeral key exchanges, then the fact that 1024bit RSA encryption is broken will not have any effect as to whether dragnet decryption of HTTPS traffic can or will occur. Unfortunately, this is not the case in our contemporary internet, and as such, we have to assume the NSA is performing dragnet decryption of non ephemeral 1024bit RSA HTTPS connections, which makes up most of the web/HTTPS traffic on the internet.

Fortunately, the open source OpenVPN was designed to use ephemeral key exchanges in order to prevent any kind of mass dragnet decryption. This still leaves OpenVPN connections open to targeted man in the middle attacks assuming they have cracked the private key. We have put in motion several changes that will harden our service and, thus, prevent these new, powerful attacks from occurring.

Kryptonite is not the only weakness
There is yet another less-likely scenario as to what could be broken. It is possible that the 1024bit Diffie Helman key exchange protocol can be cracked in a reasonable amount of time. No one has mentioned anything about this and therefore we believe it unlikely to be the case. However, this would potentially allow the NSA to decrypt past or future OpenVPN or HTTPS sessions (using a 1024bit key exchange) that they may have passively recorded. Although this is most likely not the case, we at Private Internet Access have already upgraded all of our Diffie Helman key exchanges to 2048bit to ensure that this is not even a realistic possibility.

National Security Agency
According to The Guardian, “Documents show that Edgehill’s initial aim was to decode the encrypted traffic certified by three major (unnamed) internet companies and 30 types of Virtual Private Network (VPN) – used by businesses to provide secure remote access to their systems. By 2015, GCHQ hoped to have cracked the codes used by 15 major internet companies, and 300 VPNs.”

This statement was, at first, alarming. However, after we analyzed all of the reports thoroughly as well as consulted subject matter experts both in-house and externally, we are in belief that they are referring to different types or implementations of PPTP VPN solutions including hardware, software, or even open source PPTP implementations. After all, PPTP has historically used many cryptographic algorithms that were subsequently proven to be broken or weakened to the point of uselessness. In addition, it’s also an extremely aged/legacy protocol, so there are most likely many different variants included in commercial offerings. We believe the NSA is merely referring to attempts to set up their systems to automatically detect and decrypt all of the different PPTP variants. This would, of course, enable them to obtain traffic from many large organizations, institutions, and even some governments that still use these expensive legacy commercial systems.

A second, less likely (update: this is seeming much more likely than we originally estimated), possibility is that they are referring to cracking commercial IPSec VPN offerings. This is probably not the case, because IPSec is a much more secure protocol which uses the same building blocks as TLS. With that said, there are still many possibilities where the NSA could have either found or coerced weaknesses into commercial hardware IPSec offerings. For example, this could include something similar to the HTTPS issue where non ephemeral key exchanges are used, using weak or broken cryptographic primitives, random number generator weaknesses where the NSA can predict the random numbers, or flaws in the IPSec implementation which could leak secret information.

A third possibility is that they are referring to network routing technologies which are sometimes referred to as VPNs and may or may not even be encrypted, such as MPLS.

We do not believe that they are referring to OpenVPN in any way, shape or form at this time based on the statements that have been made. OpenVPN relies on the same cryptographic building blocks as TLS, is built as an open source project, always uses ephemeral key exchanges, and finally, must be interoperable with all other OpenVPN protocol/versions. These 4 facts make it extremely unlikely that there is some fatal flaw in OpenVPN which makes it subjectable to decryption in a dragnet fashion by the NSA. Even Schneier agrees when he states, “Try to use public-domain encryption that has to be compatible with other implementations.”

Private Internet Access has got your back
As stated above, we have already increased our key exchange security to 2048bit preventing any sort of unknown NSA cracking ability. In addition, within a few weeks, we will be releasing a new client that will allow people to select how much security they want, both for the certificate and the key exchange, as well as the symmetric cipher security. Our default certificate will be 2048bit, but we will allow users to choose both 3072bit and 4096bit if they want to be especially cautious. We will also be adding support for something no other provider is currently offering called Elliptic Curve Cryptographic security, with both 256bit and 521bit curves. This is cutting edge cryptography that we want to make available to our users who choose to use it.

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  1. a disc is round

    Why does ECC “may decrease your safety”? — as shown in client advanced encryption settings.

    8 years ago