In aposton Wednesday , researcher Alex Halderman and Nadia Heninger presented compelling inquiry suggesting that the NSA has acquire the capacity to decrypt a large number of HTTPS , SSH , and VPN connexion using an onset on usual implementations of the Diffie - Hellman key telephone exchange algorithm with 1024 - bit prime of life . in the first place in the year , they were part of a research group thatpublisheda study of the Logjam attack , whichleveragedoverlooked and out-of-date codification to enforce “ export - degree ” ( downgraded , 512 - flake ) parameter for Diffie - Hellman . By execute a cost analysis of the algorithm with stronger 1024 - bit parameters and liken that with what we know of the NSA “ mordant budget ” ( and read between the lines of several leak out written document about NSA interception capabilities ) they concluded that it ’s potential NSA has been break 1024 - bit Diffie - Hellman for some time now .
The good newsworthiness is , in the meter since this research was originally published , the major web browser seller ( IE , Chrome , and Firefox ) have removed support for 512 - bit Diffie - Hellman , addressing the biggest exposure . However , 1024 - flake Diffie - Hellman remains supported for the forseeable future tense despite its exposure to NSA surveillance . In this station , we present some pragmatic lead to protect yourself from the surveillance machine , whether you ’re using a web internet browser , an SSH client , or VPN software .
Disclaimer : This is not a complete scout , and not all software system is hatch .
Web Browser
To ensure you ’re using the strongest crypto , you have to look at the encryption algorithms ( or cipher rooms ) that your web browser supports . There ’s an excellent pecker , How ’s My SSL ? , that will to quiz your web internet browser ’s cipher rooms support . The relevant area of the varlet is the bottom , Given Cipher Suites . You require to ensure that you do n’t see the text edition “ _ DHE _ ” in the list of ciphersuites . Although the Elliptic Curve version of Diffie - Hellman , typify by suite with “ _ ECDHE _ ” is okay ) . Here ’s how to off those “ _ DHE _ ” cipher fit if you still have them :
Firefox
( examine with 40.0.3 )
give a new tab , enter “ about : config ” into the location legal community and hit the “ Enter ” key . If you get a warning pageboy , tick “ I ’ll be careful , I assure ! ” This will fetch you to the Firefox conformation configurations . In the search prevention up top , case “ .dhe _ ” and strike the “ Enter ” key . This should leave in two preferences being display : “ security.ssl3.dhe_rsa_aes_256_sha ” and “ security.ssl3.dhe_rsa_aes_256_sha ” . doubly - click both of them to transfer the value from “ true ” to “ false ” .
Now , if you refresh theHow ’s My SSLpage , the “ _ DHE _ ” ciphersuites should be gone !
Chrome
After following these steps in the following operating system , refresh theHow ’s My SSLpage , the “ _ DHE _ ” ciphersuites should be lead . Note that the hex values for the shitlist correspond to theTLS Cipher Suite Registry
( tested with 2025-03-20.71 , OSX 10.10.5 )
Open “ automator ” and two-fold - click “ Run Shell Script ” . Replace the “ kat ” program line with the following :
/Applications / Google Chrome.app/Contents/MacOS/Google Chrome – cipher - suite - blacklist=0x0033,0x0039,0x009E,0xcc15
Save the program to your applications pamphlet with whatever file name you care . In view finder , you could drag the practical software to your dock and utilise that to launch Chrome without the vulnerable zero .
( tested with 2025-02-23.71 , Windows 7 )
Right - click the shortcut to your Chrome program , click “ property ” and then add the following to the end of the “ target ” : “ — cipher - suite - blacklist=0x0033,0x0039,0x009E,0xcc15 ”
The object then should be interchangeable to the following :
“ speed of light : Program Files ( x86)GoogleChromeApplicationchrome.exe ” – cipher - suite - blacklist=0x0033,0x0039,0x009E,0xcc15
From now on , open Chrome from this shortcut .
Tested with 2025-05-14.13 , Ubuntu 14.04 LTS
Starting chrome from the command line with the following flag removes the undesired ciphers :
google - chrome – cipher - suite - blacklist=0x0033,0x0039,0x009E,0xcc15
SSH
An excellent guide for harden your SSH form was released after revelations that the NSA can sometimes decode SSH connection . The guide is availablehere .
VPN
OpenVPN
Most VPN software supports the “ .ovpn ” file extension used by OpenVPN . Many VPN providers will also put up “ .ovpn ” single file to connect using OpenVPN . We ’ll have to specify in this file that we require to be using only Diffie - Hellman with 2048 - bit peak . First , we ’ll have to make a “ dhparam ” file with the “ openssl ” dictation - line :
openssl dhparam -out /some / route / to / dh2048.pem 2048
Then , we determine that we need to apply this file cabinet ’s Diffie - Hellman parameters in the “ .ovpn ” Indian file :
resound “ dh /some / path / to / dh2048.pem ” > > myvpnfile.ovpn
When you connect now , you should be using 2048 - bit efflorescence !
This postfirst appeared on Electronic Frontier Foundation ’s blogand is republished here under Creative Commons license .
Image byYuri Samoilovunder Creative Commons permit .
EncryptionSecurity
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