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Businesses Using Millions of Flawed Certificates

Many big businesses, including firms like Deloitte, are still using SHA-1 certificates, despite the fact that SHA-1 is known to be ineffective.

In fact, 120,000 SHA-1 certificates were issued this year, according to research from Netcraft.

Nearly a million SSL certificates found in Netcraft's October SSL Survey were signed with the potentially vulnerable SHA-1 hashing algorithm, and some certificate authorities are continuing to issue more.

The latest research, dubbed the SHAppening, projects that a full SHA-1 collision could be found within 49-78 days on a 512-GPU cluster. Renting the equivalent processing time on Amazon's EC2 cloud computing service would cost only $75,000 to $120,000, Netcraft said, “which is an order of magnitude less than earlier estimates.”

The researchers point out that this represents an important alarm signal, and that the industry's plans to move away from SHA-1 by 2017 might not be fast enough.

It’s now feasible for a well-funded attacker to impersonate an SSL site that uses a publicly trusted SHA-1 certificate. Worse still, while browsers still accept SHA-1 signatures, SSL sites remain at risk even after migrating to SHA-2: if an attacker were to compromise an intermediate CA certificate signed with SHA-1, he could generate valid certificates for arbitrary domains.

The SHA-2 and SHA-3 family of cryptographic hash algorithms are now the only ones approved by the National Institute of Standards and Technology (NIST) for digital signature generation. Although the SHA-2 family includes SHA-224, only the stronger SHA-256, SHA-384 and SHA-512 algorithms are allowed by the CA/Browser Forum's Baseline Requirements for the issuance and management of publicly-trusted certificates.

Tod Beardsley, principal security research manager at Rapid7, said that certificate authorities need to take the lead in eliminating the use of SHA-1.

 “Certificate authorities need to step up, sooner rather than later, to replace obsolete SHA-1 certificates with the more modern and more secure SHA-2 certificates,” he said via email. “Time and technology marches on, and it’s not as if the current population of SHA-1 certs will get any harder to attack with common, off-the-shelf equipment.”

There are positive steps happening: Google announced plans last year to retire SHA-1 in its browser;

SHA-1’s weaknesses in collisions have been known publicly since at least 2005, as reported by Bruce Schneier.

He added that it’s the comfort of the familiar that appears to be the biggest obstacle in moving on from SHA-1.

“Today, there is no practical reason to continue issuing SHA-1 certs, except for the most common reason that keeps all old technology alive: institutional inertia,” he said. “This is the same force that keeps us in magstripe card readers, cleartext Internet protocols, and unchangeable, secret-yet-not-secret social security numbers, and any number of other older technologies being thrust onto a global and increasingly hostile internet.”

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