Logjam (computer security): Difference between revisions

Revision as of 20:18, 15 October 2015

Revision as of 09:23, 16 October 2015

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The version of the vulnerability reported in May 2015 used a man-in-the-middle network attacker to downgrade a [[Transport Layer Security]] (TLS) connection to use 512 bit DH export-grade cryptography, allowing him to read the exchanged data and inject data into the connection. It affects the [[HTTPS]], [[SMTPS]], and [[IMAPS]] protocols, among others.<ref>{{cite web |last1=Adrian |first1=David |last2=Bhargavan |first2=Karthikeyan |last3=Durumeric |first3=Zakir |last4=Gaudry |first4=Pierrick |last5=Green |first5=Matthew |last6=Halderman |first6=J. Alex |last7=Heninger |first7=Nadia |last8=Springall |first8=Drew |last9=Thomé |first9=Emmanuel |last10=Valenta |first10=Luke |last11=VanderSloot |first11=Benjamin |last12=Wustrow |first12=Eric |last13=Zanella-Béguelin |first13=Santiago |last14=Zimmermann |first14=Paul |title=Imperfect Forward Secrecy: How Diffie-Hellman Fails in Practice |url=https://weakdh.org/imperfect-forward-secrecy.pdf |date=October 2015}}</ref> Its CVE ID is CVE-2015-4000.<ref>https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-4000</ref>

In October 2015, researched published another paper, estimating the feasibility of the attack against 1024 bit Diffie-HellmanDiffie–Hellman primes. By design, many Diffie-HellmanDiffie–Hellman implementations use the same pregenerated prime for their field. This was considered secure, since the [[discrete log problem]] is still consider hard even if the field is known and reused. The researchers calculated the cost of creating logjam precomputation for one 1024-bit prime at hundreds of millions of USD, and noted that this was well within range of the FY2012 $10.5 billion U.S. Consolidated Cryptologic Program (which includes NSA). Because of the reuse of primes, generating precomputation for just one prime would break two-thirds of VPNs and a quarter of all SSH servers globally. The researchers noted that this attack fits claims in leaked NSA papers that NSA is able to break much current crypto.<ref name="paper" />

== Responses ==

* On May 12, 2015, Microsoft released a patch for [[Internet Explorer]].<ref>

{{cite web

| url=https://technet.microsoft.com/en-us/library/security/ms15-055.aspx

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</ref>

* On September 1, 2015, Google released a fix for the [[Google Chrome|Chrome]] browser.<ref>

{{cite web

| url=http://googlechromereleases.blogspot.com/2015/09/stable-channel-update.html