[cabfpub] Ballot - expiration of SHA1 certificates

Tom Albertson tomalb at microsoft.com
Fri Sep 12 23:12:54 UTC 2014

Hi there - sorry to drop off the face of the earth there, I was oof and got busy this week.  Great feedback!  I have attached to this email a revised ballot incorporating some of your feedback, and am writing specific responses on a few topics raised.

Best Regards and I'll see some of you next week,

@sleevi @kirik_hall  @jeremy.rowley @adriano.santoni - Tom: ballot endorsements, thank you very much.  This new ballot is somewhat amended and still requires endorsers.

bruce at entrust - I hear you on the implementation deadline of 10 Nov 2014, and why you would prefer 1 Jan 2015.  I have a similar problem with numerous deadlines that are too short and don't take into account any of my priorities.  A quick poll of CAs will show all are short of time to implement anything, and even 1 Jan 2015 doesn't work for them.  I prefer to leave our deadline short and in place, because it recognizes the urgency of moving away from SHA-1.  If CAs are actually hurting to meet this deadline I would love to hear from them, if they need more time then we can allow it on their audits etc - but I am not certain that 1 Jan 2015 is any better than 10 November 2014.

@rick_andrews @brian - OCSP, 3 uses - 1. The ResponderID construct (through KeyHash), to identify a certificate by the hash of its public key. 2. The CertID construct. 3. The signature of the OCSP response.
Tom:  Correct - Windows will enforce the SHA1 policy only on the 3) signature of the OCSP response. The SHA1 policy does not apply to any other uses of SHA1, such as the ResponderID construct, key hash or CertID.

@frank_leroy @rob.stradling @remi.pifaut - refine scope to "SHA-1withRSAencryption for signature algorithm" since SHA1 still used to compute AKI and SKI.
Tom: Again, correct - The SHA1 policy does not apply to AKI and SKI. It only applies to the signature of the certificate.

From: Bruce Morton [mailto:bruce.morton at entrust.com]
Sent: Monday, September 8, 2014 5:56 AM
To: Tom Albertson; public at cabforum.org
Subject: RE: Ballot - expiration of SHA1 certificates

Hi Tom,

Thank you for this ballot.

I have one comment and it is the implementation date of 1 November 2014. Entrust is currently challenged to meet this date and the ballot has not been approved yet. We would request that 1 November 2014 be changed to 1 January 2015. This would allow this change to be synced with a current scheduled release.

Thanks in advance for your consideration.


From: public-bounces at cabforum.org<mailto:public-bounces at cabforum.org> [mailto:public-bounces at cabforum.org] On Behalf Of Tom Albertson
Sent: Friday, September 05, 2014 6:47 PM
To: public at cabforum.org<mailto:public at cabforum.org>
Subject: [cabfpub] FW: Ballot - expiration of SHA1 certificates

Hi there,

I have produced a ballot for discussion, which aligns the Baseline Requirements (v1.1.9)  with the planned deprecation of SHA-1.   This ballot uses the dates in the Microsoft SHA-1 deprecation policy<http://blogs.technet.com/b/pki/archive/2013/11/12/sha1-deprecation-policy.aspx> as a reference, and right now only addresses SSL certs.  I think we can offer similar language for code signing certs and possibly other BRs once we have hashed this out for SSL.

New text appears as red underlined.   A small amount of text in Appendix A is proposed for deletion (black strikethrough)  The amendments relate mainly to Section 9.4 Validity Period, with minor conforming changes to Appendix A.

Special thanks to Ben and Gerv and others, who already struggled through this issue in March 2014, that ballot discussion was most instructive.  I have made no efforts to collaborate with other Forum members on this issue except to go back and forth with Kelvin and Aaron here at Microsoft on the best text to offer to represent the Microsoft policy.

Your comments and questions are appreciated, and ultimately we could use an endorser or two of the ballot measure.


Ballot NNN -expirations of SHA1 certificates (FINAL VERSION)

9.4 Validity Period

9.4.1 Subscriber Certificates
Subscriber Certificates issued after the Effective Date MUST have a Validity Period no greater than 60 months.

Except as provided for below, Subscriber Certificates issued after 1 April 2015 MUST have a Validity Period no
greater than 39 months.

Effective 1 November 2014, CAs MUST NOT issue Subscriber Certificates utilizing the SHA-1 algorithm with an Expiry Date greater than 1 January 2017.

Except as provided for below, effective 1 January 2016, CAs MUST NOT issue Subscriber Certificates that utilize the SHA-1 algorithm.

Effective 1 April 2015, CAs MAY continue to issue Subscriber Certificates with a Validity Period greater than 39
months but not greater than 60 months provided that the CA documents that the Certificate is for a system or
software that:
(a) was in use prior to the Effective Date;
(b) is currently in use by either the Applicant or a substantial number of Relying Parties;
(c) fails to operate if the Validity Period is shorter than 60 months;
(d) does not contain known security risks to Relying Parties; and
(e) is difficult to patch or replace without substantial economic outlay.

9.4.2 Root CA Certificates

The SHA-1 deprecation policy and Validity Dates DO NOT apply to Root CA certificates.  CAs MAY continue to use their existing SHA-1 Root Certificates.  CAs MUST use SHA-2 or successor hash algorithms to sign any Subscriber certificates, Subordinate CA certificates, and CRLs effective 1 January 2016.

9.4.3 Subordinate CA Certificates

Effective 1 January 2016, CAs MUST NOT issue Subordinate CA Certificates that utilize the SHA-1 algorithm.  CAs MUST NOT issue SHA-2 Subscriber certificates under SHA-1 Subordinate CA Certificates.

Appendix A - Cryptographic Algorithm and Key Requirements (Normative)

Add this note under Table 2, Subordinate CA certificates:

* SHA-1 MAY be used with RSA keys in accordance with the criteria defined in Section 9.4.3.

And amend this note at the end of the 3 tables.

* SHA-1 MAY be used with RSA keys in accordance with the criteria defined in Section 9.4.1  until SHA-256 is supported widely by browsers used by a substantial
portion of relying-parties worldwide.

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