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Re: [Dcrup] rsa-sha1 proposals

Seth Blank <seth@valimail.com> Tue, 20 June 2017 23:39 UTC

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From: Seth Blank <seth@valimail.com>
Date: Tue, 20 Jun 2017 16:38:36 -0700
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Subject: Re: [Dcrup] rsa-sha1 proposals
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On Tue, Jun 20, 2017 at 4:20 PM, Hector Santos <hsantos@isdg.net> wrote:

> Back in 2007 RFC 4871 said "In general, sha256 should always be used
>> whenever possible."  I think people have had enough warning, and if we
>> want to kill it, we should just kill it.
>>
>
> Unless whitelisted, this will create invalid SHA1 signatures from
> perfectly good domains.  New systems who initially avoid SHA1 legacy
> support will quickly learn not all systems use SHA256. i.e a quick support
> problem.
>

To me, this is exactly the point. People have had ten years to switch to
SHA-256. At this point, people will only move if the threat of breakage is
upon them. And this isn't breakage, this is a document that says using
SHA-1 is no longer acceptable, and you MUST use SHA-256. If it's the right
security recommendation, we should say it explicitly.

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