Public CAs have already moved from SHA-1 to SHA-2 for any certificate lifetimes past Jan. 1, 2017, so you should concentrate your efforts on servers and applications with public digital certificates that haven’t already moved. After that issue is resolved, start looking at your internal PKIs and relying parties. Migrating from SHA-1 to SHA-2 isn’t hard technically, but it’s a massive logistical change with tons of repercussions and requires lots of testing.
I don’t think most vendors know the ultimate kill date for SHA-1 (i.e., when it will apply to all applications and devices and cause “fatal” errors), but I would guess it will arrive sooner than later as more and more consumers move to SHA-2. The truth is you should already be there.
SHA-3 is here, but should you use it?
Although no significant cryptographic weakness has been found in SHA-2, it's considered algorithmically related to SHA-1. Most experts believe its lifecycle will be similar to that of SHA-1. NIST already approved in August 2015 a replacement cryptographic hash algorithm standard it called SHA-3. SHA-3 does not share the same mathematical properties as SHA-1 and SHA-2, and thus should be resistant to cryptographic attack longer than SHA-2.
Unfortunately, anyone thinking of delaying their SHA-2 migration in hopes of moving directly to SHA-3 will be greatly disappointed. Widespread adoption of SHA-3 is probably many years away, whereas SHA-2 is required now. If you moved to SHA-3 now, most, if not all, of your cryptographic-relying applications and devices would probably error out (saying they cannot recognize the digital certificate).
So, if you’re not already migrated to SHA-2, get going now. And when SHA-2 starts to get weakened, we can all move to SHA-3.
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