From the shattered website:
You can use the online tool above to submit files and have them checked for a cryptanalytic collision attack on SHA-1. The code behind this was developed by Marc Stevens (CWI) and Dan Shumow (Microsoft) and is publicly available on GitHub.
It is based on the concept of counter-cryptanalysis and it is able to detect known and unknown SHA-1 cryptanalytic collision attacks given just a single file from a colliding file pair.
Is Hardened SHA-1 vulnerable?
No, SHA-1 hardened with counter-cryptanalysis (see ‘how do I detect the attack’) will detect cryptanalytic collision attacks. In that case it adjusts the SHA-1 computation to result in a safe hash. This means that it will compute the regular SHA-1 hash for files without a collision attack, but produce a special hash for files with a collision attack, where both files will have a different unpredictable hash.
finally from the GitHub pages - which I assume is called "hardened" SHA-1 above:
... More specifically they will detect any cryptanalytic collision attack against SHA-1 using any of the top 32 SHA-1 disturbance vectors with probability 1:
I(43,0), I(44,0), I(45,0), I(46,0), I(47,0), I(48,0), I(49,0), I(50,0), I(51,0), I(52,0), I(46,2), I(47,2), I(48,2), I(49,2), I(50,2), I(51,2), II(45,0), II(46,0), II(47,0), II(48,0), II(49,0), II(50,0), II(51,0), II(52,0), II(53,0), II(54,0), II(55,0), II(56,0), II(46,2), II(49,2), II(50,2), II(51,2)
What precisely are these vectors? Could there be other vectors that are vulnerable? How much protection does "hardened" SHA-1 offer?