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<div class="document" id="signature">
<h1 class="title">signature</h1>
<h2 class="subtitle" id="add-a-digital-signature-to-the-image">Add a digital signature to the image</h2>
<div class="contents topic" id="contents">
<p class="topic-title first">Contents</p>
<ul class="simple">
<li><a class="reference internal" href="#finalizesignature" id="id9">FinalizeSignature</a></li>
<li><a class="reference internal" href="#getsignatureinfo" id="id10">GetSignatureInfo</a></li>
<li><a class="reference internal" href="#signatureimage" id="id11">SignatureImage</a></li>
<li><a class="reference internal" href="#transformsignature" id="id12">TransformSignature</a></li>
<li><a class="reference internal" href="#updatesignature" id="id13">UpdateSignature</a></li>
</ul>
</div>
<div class="section" id="finalizesignature">
<h1><a class="toc-backref" href="#id9">FinalizeSignature</a></h1>
<div class="section" id="synopsis">
<h2>Synopsis</h2>
<pre class="literal-block">
FinalizeSignature( <a class="reference external" href="../api/types.html#signatureinfo">SignatureInfo</a> *signature_info );
</pre>
</div>
<div class="section" id="description">
<h2>Description</h2>
<p>Method FinalizeSignature finalizes the SHA message digest computation.</p>
<p>The format of the FinalizeSignature method is:</p>
<pre class="literal-block">
FinalizeSignature( <a class="reference external" href="../api/types.html#signatureinfo">SignatureInfo</a> *signature_info );
</pre>
<p>A description of each parameter follows:</p>
<dl class="docutils">
<dt>signature_info:</dt>
<dd>The address of a structure of type SignatureInfo.</dd>
</dl>
</div>
</div>
<div class="section" id="getsignatureinfo">
<h1><a class="toc-backref" href="#id10">GetSignatureInfo</a></h1>
<div class="section" id="id1">
<h2>Synopsis</h2>
<pre class="literal-block">
GetSignatureInfo( <a class="reference external" href="../api/types.html#signatureinfo">SignatureInfo</a> *signature_info );
</pre>
</div>
<div class="section" id="id2">
<h2>Description</h2>
<p>Method GetSignatureInfo initializes the SHA message digest structure.</p>
<p>The format of the GetSignatureInfo method is:</p>
<pre class="literal-block">
GetSignatureInfo( <a class="reference external" href="../api/types.html#signatureinfo">SignatureInfo</a> *signature_info );
</pre>
<p>A description of each parameter follows:</p>
<dl class="docutils">
<dt>signature_info:</dt>
<dd>The address of a structure of type SignatureInfo.</dd>
</dl>
</div>
</div>
<div class="section" id="signatureimage">
<h1><a class="toc-backref" href="#id11">SignatureImage</a></h1>
<div class="section" id="id3">
<h2>Synopsis</h2>
<pre class="literal-block">
unsigned int SignatureImage( <a class="reference external" href="../api/types.html#image">Image</a> *image );
</pre>
</div>
<div class="section" id="id4">
<h2>Description</h2>
<p>SignatureImage() computes a message digest from an image pixel stream with
an implementation of the NIST SHA-256 Message Digest algorithm. This
signature uniquely identifies the image and is convenient for determining
if an image has been modified or whether two images are identical.</p>
<p>The format of the SignatureImage method is:</p>
<pre class="literal-block">
unsigned int SignatureImage( <a class="reference external" href="../api/types.html#image">Image</a> *image );
</pre>
<p>A description of each parameter follows:</p>
<dl class="docutils">
<dt>image:</dt>
<dd>The image.</dd>
</dl>
</div>
</div>
<div class="section" id="transformsignature">
<h1><a class="toc-backref" href="#id12">TransformSignature</a></h1>
<div class="section" id="id5">
<h2>Synopsis</h2>
<pre class="literal-block">
TransformSignature( <a class="reference external" href="../api/types.html#signatureinfo">SignatureInfo</a> *signature_info );
</pre>
</div>
<div class="section" id="id6">
<h2>Description</h2>
<p>TransformSignature() transforms the SHA message digest.</p>
<p>The format of the TransformSignature method is:</p>
<pre class="literal-block">
TransformSignature( <a class="reference external" href="../api/types.html#signatureinfo">SignatureInfo</a> *signature_info );
</pre>
<p>A description of each parameter follows:</p>
<dl class="docutils">
<dt>signature_info:</dt>
<dd>The address of a structure of type SignatureInfo.</dd>
</dl>
</div>
</div>
<div class="section" id="updatesignature">
<h1><a class="toc-backref" href="#id13">UpdateSignature</a></h1>
<div class="section" id="id7">
<h2>Synopsis</h2>
<pre class="literal-block">
UpdateSignature( <a class="reference external" href="../api/types.html#signatureinfo">SignatureInfo</a> *signature_info, const unsigned char *message,
const size_t length );
</pre>
</div>
<div class="section" id="id8">
<h2>Description</h2>
<p>UpdateSignature() updates the SHA message digest.</p>
<p>The format of the UpdateSignature method is:</p>
<pre class="literal-block">
UpdateSignature( <a class="reference external" href="../api/types.html#signatureinfo">SignatureInfo</a> *signature_info, const unsigned char *message,
const size_t length );
</pre>
<dl class="docutils">
<dt>signature_info:</dt>
<dd>The address of a structure of type SignatureInfo.</dd>
<dt>message:</dt>
<dd>the message</dd>
<dt>length:</dt>
<dd>The length of the message.</dd>
</dl>
</div>
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