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Gradually sunsetting SHA-1

googleonlinesecurity.blogspot.com

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Re: Gradually sunsetting SHA-1

#51

Post by userbinator »

rdl wrote: post #32

I'm glad to see people move off old browsers, in general. SHA1 is far from the biggest problem with Windows XP SP2; in fact, I'd probably say SHA1 is one of the most secure aspects of the OS. The actual weaknesses in SHA1 which have been identified are very serious, but still requiring on the order of 2^61 operations to cause a collision, and there is a fairly indirect path between hash collision and end of the world…

The problem I have is how Google is doing this.

Google acting like they control the whole Internet and that everyone will yield to their power is nothing new; sadly, in some ways that is probably true.

Re: Gradually sunsetting SHA-1

#52

Post by rdl »

userbinator wrote: post #51
rdl wrote: post #32

I'm glad to see people move off old browsers, in general. SHA1 is far from the biggest problem with Windows XP SP2; in fact, I'd probably say SHA1 is one of the most secure aspects of the OS. The actual weaknesses in SHA1 which have been identified are very serious, but still requiring on the order of 2^61 operations to cause a collision, and there is a fairly indirect path between hash collision and end of the world…

The problem I have is how Google is doing this. Google acting like they control the whole Internet and that everyone will yield to their power is nothing new; sadly, in some ways that is probably true.

It's probably true, but they honestly largely use this power responsibly. I don't even really have a problem with the action here, just the timing and means of announcement.

Re: Gradually sunsetting SHA-1

#53

Post by soccerdave »

ivanr wrote: post #9

By the way, this blog post does not mention that Microsoft already effectively killed SHA1 last year when it announced that it wouldn't accept SHA1 certificates after 2016: http://blogs.technet.com/b/pki/archive/2013/11/12/sha1-depre...

After reading that blog post from Microsoft, I believe even stronger now that Google is approaching this carelessly. Microsoft announced this almost a year ago and yet the blog post reads that they are giving until January 1st 2017 until they will stop accepting SHA-1 certs. Google announced this today and starting in 22 days they will be showing a Yellow Lock on my certificate just because the cert is set to expire AFTER January 1st, 2017. That is very different approaches!

Re: Gradually sunsetting SHA-1

#54

Post by fryguy »

zobzu wrote: post #14

I feel a bit uneasy with having the "unsafe" when SHA1 is technically still safe - just not as safe as, say, sha256 (which is itself probably not as safe as sha512, etc.). It would be nice to have a better "marker" for it instead of having a very fast deprecation rate.

Many uses for hashing algorithms don't care about collision resistance (HMAC/passwords). Signatures/Certificates are not one of those things.

Re: Gradually sunsetting SHA-1

#55

Post by timewasted »

I had previously written a simple program to check the expiration dates of SSL certs, and warn if the date is approaching. After reading this (and the Microsoft article), I updated it to check signature algorithms as well. If anyone is interested in such a program: https://github.com/timewasted/go-check-certs

Re: Gradually sunsetting SHA-1

#56

Post by rstupek »

soccerdave wrote: post #45
eastdakota wrote: post #40

Earlier quoted context omitted.

Yes. Both those certificates are affected. If I had to guess, Google will begin issuing a non-SHA1 cert to modern browser users and a SHA1 certificate to older browsers before the end of September. I wish I could give you easy advice on how to do that yourself.

Thanks for the reply, I thought I was understanding it correctly. Now that I think about it more, they will still be able to use SHA-1 and not be affected because they will surely just issue another certificate that only lasts 1 year which means it will expire before January 2016, so it will still show up as Green in Chrome. Sucks for me because we paid for a cert through July 2017 and now we'll probably have to pay…

your CA should offer you free re-issuing any time you want to regenerate it

Re: Gradually sunsetting SHA-1

#57

Post by bzbarsky »

tbrownaw wrote: post #49
eastdakota wrote: post #40

Earlier quoted context omitted.

Yes. Both those certificates are affected. If I had to guess, Google will begin issuing a non-SHA1 cert to modern browser users and a SHA1 certificate to older browsers before the end of September. I wish I could give you easy advice on how to do that yourself.

How? I would expect anything that might identify the browser would be sent after the encryption was set up?

The list of supported cyphersuites is sent before the encryption is set up.

Though some browsers lie in that list and list things they don't actually support, of course...

Re: Gradually sunsetting SHA-1

#58

Post by paulannesley »

soccerdave wrote: post #53
ivanr wrote: post #9

By the way, this blog post does not mention that Microsoft already effectively killed SHA1 last year when it announced that it wouldn't accept SHA1 certificates after 2016: http://blogs.technet.com/b/pki/archive/2013/11/12/sha1-depre...

After reading that blog post from Microsoft, I believe even stronger now that Google is approaching this carelessly. Microsoft announced this almost a year ago and yet the blog post reads that they are giving until January 1st 2017 until they will stop accepting SHA-1 certs. Google announced this today and starting in 22 days they will be showing a Yellow Lock on my certificate just because the cert is set to expire…

Presumably the thinking is that certs shouldn't be issued with a validity more than a year or two. So certs expiring 2017 shouldn't be issued before 2015 or 2016… plenty of time for people to start issuing newer certs with stronger hashing. And if they don't… it's just a small visual warning, for now. Other than not getting this started sooner, it seems fine to me.

Re: Gradually sunsetting SHA-1

#59

Post by v13inc »

agl wrote: post #37
rdl wrote: post #32

I'm glad to see people move off old browsers, in general. SHA1 is far from the biggest problem with Windows XP SP2; in fact, I'd probably say SHA1 is one of the most secure aspects of the OS. The actual weaknesses in SHA1 which have been identified are very serious, but still requiring on the order of 2^61 operations to cause a collision, and there is a fairly indirect path between hash collision and end of the world…

This was already announced by Microsoft last year: https://technet.microsoft.com/en-us/library/security/2880823... Unfortunately, many CAs decided to ignore it, presumably on the assumption that Microsoft would be forced to back down. We've done this dance with MD5 and 1024-bit certificates and we know how it goes. Here's a quick list of CAs that issued more than 2000 certificates extending into 2017 with SHA-1: Glob…

You keep bringing up Microsoft without mentioning thhat they gave their users 2 years of notice, while you are giving your users less then 6 months.

Re: Gradually sunsetting SHA-1

#60

Post by v13inc »

agl wrote: post #28
Dylan16807 wrote: post #18

Earlier quoted context omitted.

It specifically says the dates apply to the end entity . They're not trying to get people off SHA1 in a couple months, they're trying to get them off in a year or two.

Just to clarify: the other replies are correct. The logic is that if the leaf certificate has an expiry after Dec 31st, 2015 then the whole chain must be SHA-256. If the leaf expires before that, then other certificates in the chain don't matter. If you have a one year certificate (and I always recommend getting one year certificates so that these issues don't affect you and so that renewal becomes an annual chore, n…

Why can't you just verify that the whole chain is SHA-1 instead of using the expiration date as a heuristic?
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