XML Encryption Syntax

• Namespace URI http://www.w3.org/2001/04/xmlenc# (Normally mapped to the xenc prefix)

• Uses some elements from XML digital signatures for keys

• Typical form:

  <EncryptedData Id="unique_value" 
        Type="http://www.w3.org/2001/04/xmlenc#Element |
        http://www.w3.org/2001/04/xmlenc#Content |
        MIME media type URI">
    <EncryptionMethod Algorithm="URI"/>
    <ds:KeyInfo>
      <ds:KeyName>Plain text name of key</ds:KeyName>
      <ds:RetrievalMethod URI="key location"
       Type="http://www.w3.org/2001/04/xmlenc#EncryptedKey" />
    </ds:KeyInfo>
    <CipherData Nonce="Base-64 encoded salt">
      <CipherValue>Base-64 encoded cipher text</CipherValue>
      <CipherReference URI="URL of cipher text">
        <Transforms>
          <ds:Transform 
            Algorithm="http://www.w3.org/TR/1999/REC-xpath-19991116">
            <ds:XPath xmlns:rep="http://www.example.org/repository">
               self::text()[parent::CipherValue[@id="example1"]]
            </ds:XPath>
          <ds:Transform>
          <ds:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#base64"/>
        </Transforms>
      </CipherReference>
    </CipherData>
  </EncryptedData>

• At a minimum, each EncryptedData must contain a CipherData which contains either a CipherValue or a CipherReference. Everything else is optional.