Re: [xcbf] Interpretation of the CS under ballot

[Bancroft Scott <baos@oss.com>]

On Thu, 10 Apr 2003, Phillip H. Griffin wrote:

> Alessandro,
>
> By these remarks, you seem very confused. Please see below.

I too am confused.  I'm re-reading what you wrote below, and rereading the
XCBF document and I am not sure what is meant.

One interpretation of what you wrote can be seen in the response I just
sent - that the value is first encoded in Base64 then in HEX.  I assumed
that this is what you meant since throughout the document it says that the
encoding rules in use is XER, which implies that Base64 cannot be visible
without first decoding the value.

Another interpretation of what you wrote is that the value is encoded in
Base64 in lieu of HEX.  That is, the Base64 encoding is not wrapped in
HEX.  Is this the case?  If so, it contradicts what is said throughout the
XCBF document - that the values are encoded according to XER, for the
version of XER that the document claims to conform to does not support
Base64 encodings.

The document is in need of clarification on this point.

Bancroft

> Alessandro Triglia wrote:
>
> >Phil, All,
> >
> >Please confirm my interpretation of the XCBF CS document in the
> >following two areas:
> >
> >1) Use of BASE64
> >2) Use of CXER vs. BASIC-XER
> >
> >
> >As for (1), my interpretation is that  ***BASE-64 must NOT be used in
> >actual encodings and message exchanges***,  despite the sentence (line
> >1542) that mentions use of BASE-64 for certificates to  "minimize their
> >size when represented using XML markup"
> >
> >
> The document states clearly at line 1018 that for both the "crls" and
> "certificates" components of  type "SignedData",
>
> "This component shall contain a Base64 armored value. "
>
> This is the opposite of your interpretation.
>
> >As for (2), my interpretation is that  ***CXER, and only CXER, must be
> >used for encoding the WHOLE messages***,  despite the numerous sentences
> >such as  "This value is always encoded using the XML Encoding Rules"
> >and the numerous exampes of BASIC-XER encoding.
> >
> >
> Clearly, since CXER is a subset of XER, CXER may be used to
> encode entire messages. But this is not required. As you say above,
> there are numerous sentences in the document such as
>
> "This value is always encoded using the XML Encoding Rules"
>
> and it is these sentences that specify all of the CXER requirements.
>
> If you carefully examine all cases, you will see that a canonical
> encoding of XER is only required for cryptographic processing
> of protected message components, and not for the message
> wrapper.
>
> This requirement is identical for the same message schemas when
> they are encoded in BER and DER in X9.84. This should come as
> no surprise, as it is common practice in many cryptographic protocols.
>
> The idea is to give implementers flexibility in what they send in all
> places in the message where doing so does not affect inter working
> of implementations. Where additional rigor is required, a canonical
> encoding is specified.
>
> As an example that may be familiar to many people involved in
> security, consider X.509 certificates. The signed content must be
> encoded in the canonical DER encoding rules. But the wrapper
> that encapsulates the signed content may be encoded using the
> Basic Encoding Rules of ASN.1. XCBF signed objects are
> treated the same.
>
> Phil
>
> >I think that, if my interpretations above are the same as other
> >people's, the current imprecisions in the document should not prevent
> >its progress.  However, I strongly wish that assurance.
> >
> >Alessandro
> >
> >
> >
> >
> >
>
>
>