I saw that Microsoft is phasing out SHA-1 support as of Jan. 1, 2016, but nearly all of the production Web servers...
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on the Internet still use it, including ours. In the wake of Heartbleed, is it time to prioritize the transition to the SHA-2 algorithm, and if so, how should we go about it?
More than half a million SSL certificates have been potentially compromised as a result of the Heartbleed vulnerability. Affected certificates should be revoked and reissued as a matter of urgency, and administrators would be wise to take advantage of this forced change to migrate to the SHA-2 cryptographic algorithm instead of using the less-secure SHA-1 algorithm.
Nearly 200,000 valid third-party certificates are now signed with SHA-2, yet this still only accounts for 6.6% of all valid third-party certificates currently in use on the Web. In the wake of the Heartbleed flaw, the total number of certificates signed with SHA-2 has jumped by more than 50%. As the migration to SHA-2 is inevitable, it makes sense even for those not affected by Heartbleed to plan for the transition now.
Practical attacks against the SHA-1 algorithm are close to being in reach of government agencies, potentially enabling attackers to impersonate secure websites. SHA-2 doesn't suffer from SHA-1's mathematical weaknesses and offers hash functions with digest lengths of 224-, 256-, 384- or 512-bits with SHA-256 and SHA-512 the most commonly used. The majority of SSL certificates are using 2048-bit keys, and at this point there is no need to consider a longer key length unless a certificate is being used for an extended period of time (such as an in-house certificate authority or an OpenPGP primary key). Some hardware -- including smart cards and readers -- don't yet support keys bigger than 2048-bits, and longer keys use more CPU cycles during encryption and authentication. The NIST speculates that 2048-bit keys will be valid up to about the year 2030.
SHA-2 certificates are compatible with most updated modern Web browsers, OS platforms, mail clients and mobile devices. For enterprises running their own websites, webmasters need to request new SHA-2 certificates to replace any certificates using SHA-1 and expiring after January 1, 2017, otherwise their servers will not be trusted by Windows-based devices (all Windows devices will stop trusting SHA-1 certificates after this date).
Legacy systems that make SSL connections along with software and hardware (such as games consoles, phones and embedded devices) that rely on hard-coded certificates will require a well-tested migration plan to ensure that any certificate replacement doesn't cause major disruptions or break existing technologies. Certain software may also need updating if it is unable to support SHA-2 encryption.
Wherever possible, use one of the two established crypto libraries -- either Windows Crypto library or OpenSSL. Both support SHA-2.
If you start the migration process now, 15 months should be plenty of time to make the necessary changes and avoid a situation where mission-critical systems become reliant on insecure protocols.
Note: Certificate usage statistics by Netcraft.
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