Re: [Trans] Angle brackets in the PRIVATE option (Ticket #1)

Peter Bowen <pzbowen@gmail.com> Sat, 29 March 2014 03:25 UTC

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Date: Fri, 28 Mar 2014 20:24:57 -0700
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From: Peter Bowen <pzbowen@gmail.com>
To: Rick Andrews <Rick_Andrews@symantec.com>
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Cc: "Rob Stradling \(rob.stradling@comodo.com\)" <rob.stradling@comodo.com>, "trans@ietf.org" <trans@ietf.org>
Subject: Re: [Trans] Angle brackets in the PRIVATE option (Ticket #1)
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On Fri, Mar 28, 2014 at 9:46 AM, Rick Andrews <Rick_Andrews@symantec.com> wrote:
> We see another potential issue with the proposed PRIVATE option. Rob’s
> current proposal would have us replace a domain label with the literal
> string “<PRIVATE>” (without the quotes). However, we try to encode DN
> components as PrintableString where possible, and angle brackets are not
> part of the PrintableString set (the lowercase letters 'a' through 'z',
> uppercase letters 'A' through 'Z', the digits '0' through '9', eleven
> special characters ' = ( ) + , - . / : ? and space).
>
> As a result, the type of the DN component would be PrintableString in the
> real cert but utf8String in the pre-certificate, and that would cause
> problems. I suggest using parentheses instead of angle brackets.

Instead of having "<PRIVATE>", what about replacing the redacted
string with a prefixed checksum of the part?

Assuming we specify CRC-32 with "+" as the prefix,
"mail.corp.example.com" would become "+6f993bb2.example.com".  This
could also allow redacting only some labels:
"mail.secret.example.gov.xx" could become
"mail.+734313b7.example.gov.xx".  This has the benefit of providing
privacy while allowing stronger matching of the certificate.

Thanks,
Peter