A method has an attribute boundary

XMLDSIG's two direct SignedInfo method declarations each have one required
attribute: Algorithm. DocFence
0.64.0
now enforces that small attribute grammar before treating a recognized OPC
package signature as structurally valid.

Parameters are children, not attributes

XMLDSIG's CanonicalizationMethodType
and SignatureMethodType
require Algorithm and declare no other attributes. Their schemas
do permit parameter elements, so DocFence keeps that distinction explicit:

<ds:CanonicalizationMethod
    Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315">
  <method:Parameter xmlns:method="urn:example"/>
</ds:CanonicalizationMethod>

<ds:SignatureMethod
    Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha256">
  <method:Parameter xmlns:method="urn:example"/>
</ds:SignatureMethod>
~~~

In 0.64, an extra or missing attribute closes the recognized signature shape.
Parameter child markup remains outside this bounded check; DocFence does not
parse a parameter, execute canonicalization, recompute a digest, or verify
XMLDSIG.

## A small rule at the right boundary

The check belongs where DocFence already requires the fixed direct
<code>SignedInfo</code> order: <code>CanonicalizationMethod</code>,
<code>SignatureMethod</code>, then one or more references. The
canonicalization URI must still be one of OPC's two permitted forms, and the
signature-method URI must still be nonblank. This prevents unrecognized method
attributes from being treated as ordinary metadata without turning DocFence
into a general XMLDSIG validator.

## Evidence and use

The 73-test suite now rejects an extra attribute on either method while
accepting schema-permitted parameter children. Across the 29 DOCX files in the
public [OOXML Signature Security
artifacts](https://github.com/RUB-NDS/OOXML_Signature_Security), all 21
parseable signature parts use only <code>Algorithm</code> on both method kinds.
Every captured profile outcome matches 0.63 byte-for-byte.

Two independent epoch-fixed builds were byte-identical. SHA-256: wheel
<code>b5ae20ee7164ce323a77776d42d8568e71b1b7ea7a0d31694e84bb6cb7b7ad42</code>;
source distribution
<code>a4a23e70d3e0ee419ebedfc57f3f4b447f72e55541bcd61f841480db1ba1a8ba</code>.

~~~bash
python -m pip install https://github.com/SybilGambleyyu/docfence/releases/download/v0.64.0/docfence-0.64.0-py3-none-any.whl

docfence check approved.docx candidate.docx --policy docfence.yml --format sarif --output docfence.sarif
~~~

Read the canonical [DocFence 0.64 release note](https://sybilgambleyyu.github.io/posts/docfence-640.html)
for the exact policy, threat-model, and validation boundaries.