rfc2803.txt

<VC++网络游戏建摸与实现>源代码

   - 0x00  0x00
   - PI data in UTF-16BE stream (variable length)

   public byte[] getDigest(String digestAlgorithm) {
       MessageDigest md = MessageDigest.getInstance(digestAlgorithm);
       md.update((byte)0);
       md.update((byte)0);
       md.update((byte)0);
       md.update((byte)7);
       md.update(getName().getBytes("UnicodeBigUnmarked"));
       md.update((byte)0);
       md.update((byte)0);
       md.update(getData().getBytes("UnicodeBigUnmarked"));
       return md.digest();
   }

2.3.3. Attr Nodes

   The digest value of Attr nodes are defined similarly to PI nodes,
   except that we need a separator between the expanded attribute name
   and the attribute value. The '0x0000' value in UTF-16BE is allowed
   nowhere in an XML document, so it can serve as an unambiguous
   separator. The expanded name must be used as the attribute name
   because it may be qualified. Note that if the attribute is a



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   namespace declaration (either the attribute name is "xmlns" or its
   prefix is "xmlns"), the digest value is undefined and the getDigest()
   method should return null.

   - ATTRIBUTE_NODE (2) in 32 bit network-byte-ordered integer
   - Expanded attribute name in UTF-16BE stream (variable length)
   - 0x00  0x00
   - Attribute value in UTF-16BE stream (variable length)

   public byte[] getDigest(String digestAlgorithm) {
       if (getNodeName().equals("xmlns")
               || getNodeName().startsWith("xmlns:"))
           return null;
       MessageDigest md = MessageDigest.getInstance(digestAlgorithm);
       md.update((byte)0);
       md.update((byte)0);
       md.update((byte)0);
       md.update((byte)2);
       md.update(getExpandedName().getBytes("UnicodeBigUnmarked"));
       md.update((byte)0);
       md.update((byte)0);
       md.update(getValue().getBytes("UnicodeBigUnmarked"));
       return md.digest();
   }

2.3.4. Element Nodes

   Element nodes are the most complex because they consist of other
   nodes recursively. Hash values of these component nodes are used to
   calculate the node's digest so that we can save computation when the
   structure is partially changed.

   First, all the attributes except for namespace declarations must be
   collected. This list is sorted lexicographically by the expanded
   attribute names (based on Unicode character code points). When no
   surrogate characters are involved, this is the same as sorting in
   ascending order in terms of the UTF-16BE encoded expanded attribute
   names, using the string comparison operator String.compareTo() in
   Java.

   - ELEMENT_NODE (1) in 32 bit network-byte-ordered integer
   - Expanded element name in UTF-16BE stream (variable length)
   - 0x00  0x00
   - A number of non-namespace-declaration attributes in 32 bit
     network-byte-ordered unsigned integer
   - Sequence of digest values of non-namespace-declaration attributes,
     sorted lexicographically by expanded attribute names
   - A number of child nodes (except for Comment nodes) in 32bit



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     network-byte-ordered unsigned integer
   - Sequence of digest values of each child node except for Comment
     nodes (variable length) (A sequence of child texts is merged to one
     text. A zero-length text and Comment nodes are not counted as
     child)

   public byte[] getDigest(String digestAlgorithm) {
       MessageDigest md = MessageDigest.getInstance(digestAlgorithm);
       ByteArrayOutputStream baos = new ByteArrayOutputStream();
       DataOutputStream dos = new DataOutputStream(baos);
       dos.writeInt(ELEMENT_NODE);//This is stored in network byte order
       dos.write(getExpandedName().getBytes("UnicodeBigUnmarked"));
       dos.write((byte)0);
       dos.write((byte)0);
       // Collect all attributes except for namespace declarations
       NamedNodeMap nnm = this.getAttributes();
       int len = nnm.getLength()
               // Find "xmlns" or "xmlns:foo" in nnm and omit it.
       ...
       dos.writeInt(len);    // This is sorted in the network byte order
       // Sort attributes lexicographically by expanded attribute
       // names.
       ...
       // Assume that `Attr[] aattr' has sorted Attribute instances.
       for (int i = 0;  i < len;  i ++)
           dos.write(aattr[i].getDigest(digestAlgorithm));
       Node n = this.getFirstChild();
       // Assume that adjoining Texts are merged,
       // there is  no 0-length Text, and
       // comment nodes are removed.
       len = this.getChildNodes().getLength();
       dos.writeInt(len);    // This is stored in the network byte order
       while (n != null) {
           dos.write(n.getDigest(digestAlgorithm));
           n = n.getNextSibling();
       }
       dos.close();
       md.update(baos.toByteArray());
       return md.digest();
   }











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2.3.5. Document Nodes

   A Document node may have PI nodes before and after the root Element
   node.  The digest value of a Document node is computed based on the
   sequence of the digest values of the pre-root PI nodes, the root
   Element node, and the post-root PI nodes in this order.  Comment
   nodes and DocumentType nodes, if any, are ignored.

   - DOCUMENT_NODE (9) in 32 bit network-byte-ordered integer
   - A number of child nodes (except for Comment and DocumentType nodes)
     in 32bit network-byte-ordered unsigned integer
   - Sequence of digest values of each child node except for Comment and
     DocumentType nodes (variable length)

     public byte[] getDigest(String digestAlgorithm) {
         MessageDigest md = MessageDigest.getInstance(digestAlgorithm);
         ByteArrayOutputStream baos = new ByteArrayOutputStream();
         DataOutputStream dos = new DataOutputStream(baos);
         dos.writeInt(DOCUMENT_NODE);//This is stored in network byte order

         // Assume that Comment and DocumentType nodes are removed and this
         // node has only an Element node and PI nodes.
         len = this.getChildNodes().getLength();
         dos.writeInt(len);    // This is stored in the network byte order
         Node n = this.getFirstChild();
         while (n != null) {
             dos.write(n.getDigest(digestAlgorithm));
             n = n.getNextSibling();
         }
         dos.close();
         md.update(baos.toByteArray());
         return md.digest();
     }

3. Discussion

     The definition described above can be efficiently implemented with
     any XML processor that is conformant to either DOM and SAX
     specification.  Reference implementations are available on request.

4. Security Considerations

     DOMHASH is expected to be used as the basis for digital signatures
     and other security and integrity uses.  It's appropriateness for
     such uses depends on the security of the hash algorithm used and
     inclusion of the fundamental characteristics it is desired to check
     in parts of the DOM model incorporated in the digest by DOMHASH.




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References

   [DOM]   "Document Object Model (DOM), Level 1 Specification", October
         1998, http://www.w3.org/TR/REC-DOM-Level-1/

   [MD5]   Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
         April 1992.

   [NAM]   Tim Bray, Dave Hollander, Andrew Layman, "Namespaces in XML",
         http://www.w3.org/TR/1999/REC-xml-names-19990114.

   [SAX]   David Megginson, "SAX 1.0: The Simple API for XML",
         http://www.megginson.com/SAX/, May 1998.

   [SHA]   (US) National Institute of Standards and Technology, "Federal
         Information Processing Standards Publication 180-1: Secure Hash
         Standard", 17 April 1995.

   [URI]   Berners-Lee, T., Fielding, R. and  L. Masinter, "Uniform
         Resource Identifiers (URI): Generic Syntax", RFC 2396, August
         1998.

   [UTF16] Hoffman, P., Yergeau, F., "UTF-16, an encoding of ISO 10646",
         RFC 2781, February 2000.

   [XML]   Tim Bray, Jean Paoli, C. M. Sperber-McQueen, "Extensible
         Markup Language (XML) 1.0", http://www.w3.org/TR/1998/REC-xml-
         19980210

Authors' Addresses

   Hiroshi Maruyama,
   IBM Research, Tokyo Research Laboratory

   EMail: [e-mail]


   Kent Tamura,
   IBM Research, Tokyo Research Laboratory

   EMail: [e-mail]


   Naohiko Uramoto,
   IBM Research, Tokyo Research Laboratory

   EMail: [e-mail]




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Full Copyright Statement

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
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   kind, provided that the above copyright notice and this paragraph are
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   The limited permissions granted above are perpetual and will not be
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   This document and the information contained herein is provided on an
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Acknowledgment

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















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