Stick a fork in MD5.

Reply Tue 30 Dec, 2008 03:07 pm

We have identified a vulnerability in the Internet Public Key Infrastructure (PKI) used to issue digital certificates for secure websites. As a proof of concept we executed a practical attack scenario and successfully created a rogue Certification Authority (CA) certificate trusted by all common web browsers. This certificate allows us to impersonate any website on the Internet, including banking and e-commerce sites secured using the HTTPS protocol.

Our attack takes advantage of a weakness in the MD5 cryptographic hash function that allows the construction of different messages with the same MD5 hash. This is known as an MD5 "collision". Previous work on MD5 collisions between 2004 and 2007 showed that the use of this hash function in digital signatures can lead to theoretical attack scenarios. Our current work proves that at least one attack scenario can be exploited in practice, thus exposing the security infrastructure of the web to realistic threats.

As a result of this successfull attack, we are currently in possession of a rogue Certification Authority certificate. This certificate will be accepted as valid and trusted by all common browsers, because it appears to be signed by one of the root CAs that browsers trust by default. In turn, any website certificate signed by our rogue CA will be trusted as well. If an unsuspecting user is a victim of a man-in-the-middle attack using such a certificate, they will be assured that the connection is secure through all common security indicators: a "https://" url in the address bar, a closed padlock and messages such as "This certificate is OK" if they chose to inspect the certificate.
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Reply Tue 30 Dec, 2008 10:50 pm
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Reply Wed 31 Dec, 2008 02:40 am
So...does this mean the world's gonna end and such?
Reply Wed 31 Dec, 2008 02:58 am


Microsoft: MD5 hack poses no major threats to users
Security advisory downplays danger; only recommendation is to keep Windows updated

December 30, 2008 (Computerworld) In reaction to the news today that security researchers have come up with a way to spoof the digital certificates that secure many Web sites, Microsoft Corp. downplayed the threat to users.

In a security advisory, Microsoft acknowledged the disclosure earlier in the day of an exploit of long-known bugs in the MD5 hashing algorithm used to create the digital certificates that in turn provide proof of a secure connection between users and Web sites. But the software vendor minimized the danger that users could face.

"This new disclosure does not increase risk to customers significantly, as the researchers have not published the cryptographic background to the attack, and the attack is not repeatable without this information," said Microsoft. The company added that it wasn't aware of any actual attacks using the techniques described by an international team of researchers from Germany, the Netherlands, Switzerland and the U.S.

Microsoft also noted that most of the certificate authority vendors that issue digital certificates have abandoned MD5 and upgraded to the more secure SHA-1 algorithm.

However, there are several notable exceptions that still rely on MD5, including VeriSign Inc.'s RapidSSL.com certificate authorization scheme. The researchers, who presented their findings at a security conference in Berlin today, said they in fact were able to hack RapidSSL.com and produce fake digital certificates.

More-stringent digital certificates, dubbed Extended Validation, are always signed using SHA-1, Microsoft added. "As such, [they] are not affected by this newly reported research," the company's advisory read.

Extended Validation, or EV certificates, are supported by all current Web browsers, which display a special icon or shade the address bar when the user surfs to a site secured by one. Microsoft's own Internet Explorer, for instance, turns the entire address bar green when it encounters a site secured by an EV certificate, while Mozilla Corp.'s Firefox tints part of its address bar the same color.

Although Microsoft didn't offer any specific steps for users to take to protect themselves in light of today's disclosures, it urged people to keep Windows updated with the latest software patches.

Microsoft wasn't the only company that responded to the news about the exploit of the MD5 bug. Earlier today, Mozilla also acknowledged that the MD5 algorithm could be hacked and that phony digital certificates could be created as a result.

"This is not an attack on a Mozilla product, but we are nevertheless working with affected certificate authorities to ensure that their issuing processes are updated to prevent this threat," Johnathan Nightingale, a Mozilla spokesman on security issues, wrote in an entry posted on the company's blog. Like Microsoft's advisory, Nightingale's warning also said that Mozilla hadn't seen any evidence of actual attacks.

Even so, Nightingale recommended that Firefox users remain watchful. "We advise users to exercise caution when interacting with sites that require sensitive information, particularly when using public Internet connections," he wrote.

Comment from the article site:

This article is a little misleading. MD5 is not a Microsoft product, it's an encryption algorhythm. Most signing authorities have moved on to SHA.. VeriSign though, one of the largest has not. There have been known bugs with MD5 for over a decade that potentially effect every platform and browser that uses it.

Reply Wed 31 Dec, 2008 08:41 am
Butrflynet wrote:

Comment from the article site:

This article is a little misleading. MD5 is not a Microsoft product, it's an encryption algorhythm. Most signing authorities have moved on to SHA.. VeriSign though, one of the largest has not. There have been known bugs with MD5 for over a decade that potentially effect every platform and browser that uses it.

IMO, this is the relevant information. Basically, users are dependent on the certificate authorities moving to SHA. RapidSSL, FreeSSL, TrustCenter, RSA Data Security, Thawte, and verisign.co.jp are all affected, apparently.

The researchers used 200 Playstation 3 systems, and it took them only a couple of days.
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