<div class="content"><p> The Data Segment Encryption Header MUST be formatted as
follows.</p><table>
 <tbody><tr>
  <th><p><br/>0</p></th>
  <th><p><br/>1</p></th>
  <th><p><br/>2</p></th>
  <th><p><br/>3</p></th>
  <th><p><br/>4</p></th>
  <th><p><br/>5</p></th>
  <th><p><br/>6</p></th>
  <th><p><br/>7</p></th>
  <th><p><br/>8</p></th>
  <th><p><br/>9</p></th>
  <th><p>1<br/>0</p></th>
  <th><p><br/>1</p></th>
  <th><p><br/>2</p></th>
  <th><p><br/>3</p></th>
  <th><p><br/>4</p></th>
  <th><p><br/>5</p></th>
  <th><p><br/>6</p></th>
  <th><p><br/>7</p></th>
  <th><p><br/>8</p></th>
  <th><p><br/>9</p></th>
  <th><p>2<br/>0</p></th>
  <th><p><br/>1</p></th>
  <th><p><br/>2</p></th>
  <th><p><br/>3</p></th>
  <th><p><br/>4</p></th>
  <th><p><br/>5</p></th>
  <th><p><br/>6</p></th>
  <th><p><br/>7</p></th>
  <th><p><br/>8</p></th>
  <th><p><br/>9</p></th>
  <th><p>3<br/>0</p></th>
  <th><p><br/>1</p></th>
 </tr>
 <tr>
  <td colspan="32">
  <p>Starting
  File Offset</p>
  </td>
 </tr>
 <tr>
  <td colspan="32">
  <p>...</p>
  </td>
 </tr>
 <tr>
  <td colspan="32">
  <p>Length</p>
  </td>
 </tr>
 <tr>
  <td colspan="32">
  <p>Bytes
  Within Stream Size</p>
  </td>
 </tr>
 <tr>
  <td colspan="32">
  <p>Bytes
  Within VDL</p>
  </td>
 </tr>
 <tr>
  <td colspan="16">
  <p>0x0000</p>
  </td>
  <td colspan="8">
  <p>Data Unit
  Shift</p>
  </td>
  <td colspan="8">
  <p>Chunk Shift</p>
  </td>
 </tr>
 <tr>
  <td colspan="8">
  <p>Cluster
  Shift</p>
  </td>
  <td colspan="8">
  <p>0x01</p>
  </td>
  <td colspan="16">
  <p>Number of
  Data Blocks</p>
  </td>
 </tr>
 <tr>
  <td colspan="32">
  <p>Data Block
  Sizes (variable)</p>
  </td>
 </tr>
 <tr>
  <td colspan="32">
  <p>...</p>
  </td>
 </tr>
 <tr>
  <td colspan="32">
  <p>Extended
  Header (16 bytes, optional)</p>
  </td>
 </tr>
 <tr>
  <td colspan="32">
  <p>...</p>
  </td>
 </tr>
 <tr>
  <td colspan="32">
  <p>...</p>
  </td>
 </tr>
 <tr>
  <td colspan="32">
  <p>...</p>
  </td>
 </tr>
</tbody></table><p><b>Starting File Offset (8 bytes): </b>This field
MUST contain an unsigned 64-bit integer in little-endian format denoting the
offset, in bytes, into the stream being serialized of the first data byte
contained in this data segment.</p><p><b>Length (4 bytes): </b>The length of this header,
in bytes, measured from the beginning of the <b>Starting File Offset</b> field
to the end of the <b>Data Segment Encryption Header</b>. It MUST be a 32-bit
unsigned integer in little-endian format. Any unused bytes within this
structure MUST be set to zero and ignored by the server.</p><p><b>Bytes Within Stream Size (4 bytes): </b>The number
of bytes contained within this stream data segment that fall within the stream
size. It MUST be a 32-bit unsigned integer in little-endian format. This can be
less than the number of bytes actually present due to padding required by the
encryption algorithm.</p><p><b>Bytes Within VDL (4 bytes): </b>The number of
bytes contained within this stream data segment that fall within the <a href="230807ac-20be-494f-86e3-4c8ac23ea584#gt_802f5450-7e2b-4e6d-85ec-306971174ab1" data-linktype="relative-path">valid data length (VDL)</a>. It
MUST be a 32-bit unsigned integer in little-endian format. This can be less
than the number of bytes actually present due to padding required by the
encryption algorithm. Bytes beyond the VDL MUST be set to zero after
decryption.</p><p><b>Data Unit Shift (1 byte): </b>The base-2 logarithm
of the data unit size. It MUST be an 8-bit unsigned integer. For files that are
not <a href="230807ac-20be-494f-86e3-4c8ac23ea584#gt_57c7faf0-6002-4b1a-b8fc-fc9244d5a6e5" data-linktype="relative-path">sparse files</a>, the
data unit size MUST be set to the size of the data in this segment. For sparse
files, it MUST be equal to the size of a compression unit, which is the
smallest unit that all holes MUST be a multiple of.</p><p><b>Chunk Shift (1 byte): </b>The base-2 logarithm of
the chunk size. It MUST be an 8-bit unsigned integer. The chunk size MUST be
equal to the data unit size.</p><p><b>Cluster Shift (1 byte): </b>The base-2 logarithm
of the cluster size in bytes. It MUST be an 8-bit unsigned integer. It MUST be
equal to the smallest unit of allocation in the underlying <a href="230807ac-20be-494f-86e3-4c8ac23ea584#gt_528b06a4-e67c-43b3-a02d-8738858a691d" data-linktype="relative-path">file system</a>.</p><p><b>Number of Data Blocks (2 bytes): </b>This field
MUST contain the number of data blocks specified in this segment. It MUST be a
16-bit unsigned integer in little-endian format. It MUST be equal to the number
of entries in the <b>Data Block Sizes</b> field specified next.</p><p><b>Data Block Sizes (variable): </b>This field MUST
consist of a sequence of unsigned 32-bit values in little-endian format,
denoting the sizes of the successive data blocks in the <b>Stream Data</b>
field that follows this header. Each value in the sequence MUST be less than or
equal to the data unit size, unless it spans the VDL or a hole in the case of a
sparse file.</p><p><b>Extended Header (16 bytes): </b>This field is
optional, and its presence is indicated by the four-byte signature located at
the start of this field. If this field is present, the server SHOULD interpret
it as defined in section <a href="9f6beece-d6c3-483f-a969-5af841b88f1e" data-linktype="relative-path">2.2.3.4</a>.
The server MAY ignore this field.<a id="Appendix_A_Target_20"></a><a aria-label="Product behavior note 20" href="cecd911d-7105-45cc-a7c8-348335d6f03f#Appendix_A_20" data-linktype="relative-path">&lt;20&gt;</a></p></div>