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Re: Base64 -- do we really want/need line breaks every 76 characters?

From: Martin Duerst <duerst@w3.org>
Date: Wed, 23 May 2001 09:46:52 +0900
Message-Id: <>
To: "Brian LaMacchia" <bal@microsoft.com>, <w3c-ietf-xmldsig@w3.org>
This should be fixed in XML Schema, not in Signatures, I guess.
On the other hand, it's not a bad idea to have line breaks in
the Base64, just streaming out something as a very long line
(e.g. 1000000 chars) doesn't seem like a good idea. It will
cause problems sooner or later. For example, SOAP may be used
over mail, and what happens then?

Regards,  Martin.

At 17:31 01/05/22 -0700, Brian LaMacchia wrote:
>Currently, XMLDSIG references RFC 2045 (one of the MIME RFCs) for a
>definition of Base64 encoding/decoding.  (See section 6.8 of [1].)  It
>has been pointed out to me that RFC 2045 *requires* that Base64-encoded
>content have line breaks at least every 76 characters.  Paragraph 6
>reads as follows:
>    The encoded output stream must be represented in lines of no more
>    than 76 characters each.  All line breaks or other characters not
>    found in Table 1 must be ignored by decoding software.  In base64
>    data, characters other than those in Table 1, line breaks, and other
>    white space probably indicate a transmission error, about which a
>    warning message or even a message rejection might be appropriate
>    under some circumstances.
>I can't see any reason for XMLDSIG to inherit a line-length limitation
>that appears to have been there for mail-specific reasons.  The SOAP 1.1
>submission [2] removes the line length limitation in their use of
>Base64; Section 5.4.3 of SOAP reads as follows:
>    The recommended representation of an opaque array of bytes is the
>    'base64' encoding defined in XML Schemas [10][11], which uses the
>    base64 encoding algorithm defined in 2045 [13]. However, the line
>    length restrictions that normally apply to base64 data in MIME do
>    not apply in SOAP. A "SOAP-ENC:base64" subtype is supplied for use
>    with SOAP.
>I propose that XMLDSIG adopt language similar to SOAP and not require
>applications to insert line breaks at least every 76 characters.
>(Conforming implementation will still accept line-limited encodings
>since they have to ignore any found whitespace in the Base64 string.)
>                                         --bal
>[1] http://www.ietf.org/rfc/rfc2045.txt
>[2] http://www.w3.org/TR/SOAP/
Received on Tuesday, 22 May 2001 21:23:56 UTC

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