SHA1 collisions proven possisble
Patrick W. Gilmore
patrick at ianai.net
Sun Feb 26 17:18:48 UTC 2017
On Feb 25, 2017, at 17:44, Jimmy Hess <mysidia at gmail.com> wrote:
>> On Thu, Feb 23, 2017 at 2:03 PM, Patrick W. Gilmore <patrick at ianai.net> wrote:
>> For instance, someone cannot take Verisign’s root cert and create a cert which collides
>> on SHA-1. Or at least we do not think they can. We’ll know in 90 days when
>> Google releases the code.
> Maybe. If you assume that no SHA attack was known to anybody at the
> time the Verisign
> cert was originally created, And that the process used to originally
> create Verisign's root cert
> was not tainted to leverage such attack.
> If it was tainted, then maybe there's another version of the
> certificate that was constructed
> with a different Subject name and Subject public key, but the same
> SHA1 hash, and same Issuer Name and same Issuer Public Key.
I repeat something I've said a couple times in this thread: If I can somehow create two docs with the same hash, and somehow con someone into using one of them, chances are there are bigger problems than a SHA1 hash collision.
If you assume I could somehow get Verisign to use a cert I created to match another cert with the same hash, why in the hell would that matter? I HAVE THE ONE VERISIGN IS USING. Game over.
Valdis came up with a possible use of such documents. While I do not think there is zero utility in those instances, they are pretty small vectors compared to, say, having a root cert at a major CA.
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