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<p>Galois/Counter mode for 128-bit block ciphers.
<a href="#details">More...</a></p>
<div class="textblock"><code>#include "<a class="el" href="cipher_8h_source.html">cipher.h</a>"</code><br/>
<code>#include <stdint.h></code><br/>
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Include dependency graph for gcm.h:</div>
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<div class="center"><img src="gcm_8h__incl.png" border="0" usemap="#gcm_8h" alt=""/></div>
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<p><a href="gcm_8h_source.html">Go to the source code of this file.</a></p>
<table class="memberdecls">
<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="nested-classes"></a>
Data Structures</h2></td></tr>
<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">struct  </td><td class="memItemRight" valign="bottom"><a class="el" href="structgcm__context.html">gcm_context</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">GCM context structure. <a href="structgcm__context.html#details">More...</a><br/></td></tr>
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Macros</h2></td></tr>
<tr class="memitem:a9ec162612f0f3a8b7e380c02ffc35867"><td class="memItemLeft" align="right" valign="top">#define </td><td class="memItemRight" valign="bottom"><a class="el" href="gcm_8h.html#a9ec162612f0f3a8b7e380c02ffc35867">GCM_ENCRYPT</a>   1</td></tr>
<tr class="separator:a9ec162612f0f3a8b7e380c02ffc35867"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a65cecb8f0fb02b51814bfbbae65fdd9c"><td class="memItemLeft" align="right" valign="top">#define </td><td class="memItemRight" valign="bottom"><a class="el" href="gcm_8h.html#a65cecb8f0fb02b51814bfbbae65fdd9c">GCM_DECRYPT</a>   0</td></tr>
<tr class="separator:a65cecb8f0fb02b51814bfbbae65fdd9c"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a489a0823c71a0855d61f649bd1c7f4b0"><td class="memItemLeft" align="right" valign="top">#define </td><td class="memItemRight" valign="bottom"><a class="el" href="gcm_8h.html#a489a0823c71a0855d61f649bd1c7f4b0">POLARSSL_ERR_GCM_AUTH_FAILED</a>   -0x0012</td></tr>
<tr class="memdesc:a489a0823c71a0855d61f649bd1c7f4b0"><td class="mdescLeft"> </td><td class="mdescRight">Authenticated decryption failed. <a href="#a489a0823c71a0855d61f649bd1c7f4b0">More...</a><br/></td></tr>
<tr class="separator:a489a0823c71a0855d61f649bd1c7f4b0"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a5dccf47b81f81ee37869f170613e8a91"><td class="memItemLeft" align="right" valign="top">#define </td><td class="memItemRight" valign="bottom"><a class="el" href="gcm_8h.html#a5dccf47b81f81ee37869f170613e8a91">POLARSSL_ERR_GCM_BAD_INPUT</a>   -0x0014</td></tr>
<tr class="memdesc:a5dccf47b81f81ee37869f170613e8a91"><td class="mdescLeft"> </td><td class="mdescRight">Bad input parameters to function. <a href="#a5dccf47b81f81ee37869f170613e8a91">More...</a><br/></td></tr>
<tr class="separator:a5dccf47b81f81ee37869f170613e8a91"><td class="memSeparator" colspan="2"> </td></tr>
</table><table class="memberdecls">
<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="func-members"></a>
Functions</h2></td></tr>
<tr class="memitem:aa51998d315ab0c99cff40bbe7dd7f200"><td class="memItemLeft" align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><a class="el" href="gcm_8h.html#aa51998d315ab0c99cff40bbe7dd7f200">gcm_init</a> (<a class="el" href="structgcm__context.html">gcm_context</a> *ctx, <a class="el" href="cipher_8h.html#a373f5d3a0a42c77ff4f5fe4fe7da0560">cipher_id_t</a> cipher, const unsigned char *key, unsigned int keysize)</td></tr>
<tr class="memdesc:aa51998d315ab0c99cff40bbe7dd7f200"><td class="mdescLeft"> </td><td class="mdescRight">GCM initialization (encryption) <a href="#aa51998d315ab0c99cff40bbe7dd7f200">More...</a><br/></td></tr>
<tr class="separator:aa51998d315ab0c99cff40bbe7dd7f200"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ad87f8fd2a45b5b32c545443779c48c2d"><td class="memItemLeft" align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><a class="el" href="gcm_8h.html#ad87f8fd2a45b5b32c545443779c48c2d">gcm_crypt_and_tag</a> (<a class="el" href="structgcm__context.html">gcm_context</a> *ctx, int mode, size_t length, const unsigned char *iv, size_t iv_len, const unsigned char *add, size_t add_len, const unsigned char *input, unsigned char *output, size_t tag_len, unsigned char *tag)</td></tr>
<tr class="memdesc:ad87f8fd2a45b5b32c545443779c48c2d"><td class="mdescLeft"> </td><td class="mdescRight">GCM buffer encryption/decryption using a block cipher. <a href="#ad87f8fd2a45b5b32c545443779c48c2d">More...</a><br/></td></tr>
<tr class="separator:ad87f8fd2a45b5b32c545443779c48c2d"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a61dae452f29231fe46c1bacee4c60e72"><td class="memItemLeft" align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><a class="el" href="gcm_8h.html#a61dae452f29231fe46c1bacee4c60e72">gcm_auth_decrypt</a> (<a class="el" href="structgcm__context.html">gcm_context</a> *ctx, size_t length, const unsigned char *iv, size_t iv_len, const unsigned char *add, size_t add_len, const unsigned char *tag, size_t tag_len, const unsigned char *input, unsigned char *output)</td></tr>
<tr class="memdesc:a61dae452f29231fe46c1bacee4c60e72"><td class="mdescLeft"> </td><td class="mdescRight">GCM buffer authenticated decryption using a block cipher. <a href="#a61dae452f29231fe46c1bacee4c60e72">More...</a><br/></td></tr>
<tr class="separator:a61dae452f29231fe46c1bacee4c60e72"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a44f5d26e87eda4ef3fd6ca33bdddc17a"><td class="memItemLeft" align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><a class="el" href="gcm_8h.html#a44f5d26e87eda4ef3fd6ca33bdddc17a">gcm_starts</a> (<a class="el" href="structgcm__context.html">gcm_context</a> *ctx, int mode, const unsigned char *iv, size_t iv_len, const unsigned char *add, size_t add_len)</td></tr>
<tr class="memdesc:a44f5d26e87eda4ef3fd6ca33bdddc17a"><td class="mdescLeft"> </td><td class="mdescRight">Generic GCM stream start function. <a href="#a44f5d26e87eda4ef3fd6ca33bdddc17a">More...</a><br/></td></tr>
<tr class="separator:a44f5d26e87eda4ef3fd6ca33bdddc17a"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ac27c1ae819964e256ad31076bf8be0ac"><td class="memItemLeft" align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><a class="el" href="gcm_8h.html#ac27c1ae819964e256ad31076bf8be0ac">gcm_update</a> (<a class="el" href="structgcm__context.html">gcm_context</a> *ctx, size_t length, const unsigned char *input, unsigned char *output)</td></tr>
<tr class="memdesc:ac27c1ae819964e256ad31076bf8be0ac"><td class="mdescLeft"> </td><td class="mdescRight">Generic GCM update function. <a href="#ac27c1ae819964e256ad31076bf8be0ac">More...</a><br/></td></tr>
<tr class="separator:ac27c1ae819964e256ad31076bf8be0ac"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a6544ce0fa5390ced146b041cfa8a4f88"><td class="memItemLeft" align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><a class="el" href="gcm_8h.html#a6544ce0fa5390ced146b041cfa8a4f88">gcm_finish</a> (<a class="el" href="structgcm__context.html">gcm_context</a> *ctx, unsigned char *tag, size_t tag_len)</td></tr>
<tr class="memdesc:a6544ce0fa5390ced146b041cfa8a4f88"><td class="mdescLeft"> </td><td class="mdescRight">Generic GCM finalisation function. <a href="#a6544ce0fa5390ced146b041cfa8a4f88">More...</a><br/></td></tr>
<tr class="separator:a6544ce0fa5390ced146b041cfa8a4f88"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a087a5c5e531806928a57f465447bc6f5"><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><a class="el" href="gcm_8h.html#a087a5c5e531806928a57f465447bc6f5">gcm_free</a> (<a class="el" href="structgcm__context.html">gcm_context</a> *ctx)</td></tr>
<tr class="memdesc:a087a5c5e531806928a57f465447bc6f5"><td class="mdescLeft"> </td><td class="mdescRight">Free a GCM context and underlying cipher sub-context. <a href="#a087a5c5e531806928a57f465447bc6f5">More...</a><br/></td></tr>
<tr class="separator:a087a5c5e531806928a57f465447bc6f5"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a63019d9ec7edd51b02793cdade88054a"><td class="memItemLeft" align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><a class="el" href="gcm_8h.html#a63019d9ec7edd51b02793cdade88054a">gcm_self_test</a> (int verbose)</td></tr>
<tr class="memdesc:a63019d9ec7edd51b02793cdade88054a"><td class="mdescLeft"> </td><td class="mdescRight">Checkup routine. <a href="#a63019d9ec7edd51b02793cdade88054a">More...</a><br/></td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<div class="textblock"><p>Galois/Counter mode for 128-bit block ciphers. </p>
<p>Copyright (C) 2006-2013, Brainspark B.V.</p>
<p>This file is part of PolarSSL (<a href="http://www.polarssl.org">http://www.polarssl.org</a>) Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org></p>
<p>All rights reserved.</p>
<p>This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.</p>
<p>This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.</p>
<p>You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. </p>
<p>Definition in file <a class="el" href="gcm_8h_source.html">gcm.h</a>.</p>
</div><h2 class="groupheader">Macro Definition Documentation</h2>
<a class="anchor" id="a65cecb8f0fb02b51814bfbbae65fdd9c"></a>
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<td class="memname">#define GCM_DECRYPT   0</td>
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<p>Definition at line <a class="el" href="gcm_8h_source.html#l00041">41</a> of file <a class="el" href="gcm_8h_source.html">gcm.h</a>.</p>
</div>
</div>
<a class="anchor" id="a9ec162612f0f3a8b7e380c02ffc35867"></a>
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<td class="memname">#define GCM_ENCRYPT   1</td>
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<p>Definition at line <a class="el" href="gcm_8h_source.html#l00040">40</a> of file <a class="el" href="gcm_8h_source.html">gcm.h</a>.</p>
</div>
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<a class="anchor" id="a489a0823c71a0855d61f649bd1c7f4b0"></a>
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<td class="memname">#define POLARSSL_ERR_GCM_AUTH_FAILED   -0x0012</td>
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</table>
</div><div class="memdoc">
<p>Authenticated decryption failed. </p>
<p>Definition at line <a class="el" href="gcm_8h_source.html#l00043">43</a> of file <a class="el" href="gcm_8h_source.html">gcm.h</a>.</p>
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</div>
<a class="anchor" id="a5dccf47b81f81ee37869f170613e8a91"></a>
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<td class="memname">#define POLARSSL_ERR_GCM_BAD_INPUT   -0x0014</td>
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<p>Bad input parameters to function. </p>
<p>Definition at line <a class="el" href="gcm_8h_source.html#l00044">44</a> of file <a class="el" href="gcm_8h_source.html">gcm.h</a>.</p>
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<h2 class="groupheader">Function Documentation</h2>
<a class="anchor" id="a61dae452f29231fe46c1bacee4c60e72"></a>
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<td class="memname">int gcm_auth_decrypt </td>
<td>(</td>
<td class="paramtype"><a class="el" href="structgcm__context.html">gcm_context</a> * </td>
<td class="paramname"><em>ctx</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">size_t </td>
<td class="paramname"><em>length</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">const unsigned char * </td>
<td class="paramname"><em>iv</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">size_t </td>
<td class="paramname"><em>iv_len</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">const unsigned char * </td>
<td class="paramname"><em>add</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">size_t </td>
<td class="paramname"><em>add_len</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">const unsigned char * </td>
<td class="paramname"><em>tag</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">size_t </td>
<td class="paramname"><em>tag_len</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">const unsigned char * </td>
<td class="paramname"><em>input</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">unsigned char * </td>
<td class="paramname"><em>output</em> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
</tr>
</table>
</div><div class="memdoc">
<p>GCM buffer authenticated decryption using a block cipher. </p>
<dl class="section note"><dt>Note</dt><dd>On decryption, the output buffer cannot be the same as input buffer. If buffers overlap, the output buffer must trail at least 8 bytes behind the input buffer.</dd></dl>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">ctx</td><td>GCM context </td></tr>
<tr><td class="paramname">length</td><td>length of the input data </td></tr>
<tr><td class="paramname">iv</td><td>initialization vector </td></tr>
<tr><td class="paramname">iv_len</td><td>length of IV </td></tr>
<tr><td class="paramname">add</td><td>additional data </td></tr>
<tr><td class="paramname">add_len</td><td>length of additional data </td></tr>
<tr><td class="paramname">tag</td><td>buffer holding the tag </td></tr>
<tr><td class="paramname">tag_len</td><td>length of the tag </td></tr>
<tr><td class="paramname">input</td><td>buffer holding the input data </td></tr>
<tr><td class="paramname">output</td><td>buffer for holding the output data</td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>0 if successful and authenticated, POLARSSL_ERR_GCM_AUTH_FAILED if tag does not match </dd></dl>
</div>
</div>
<a class="anchor" id="ad87f8fd2a45b5b32c545443779c48c2d"></a>
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<td class="memname">int gcm_crypt_and_tag </td>
<td>(</td>
<td class="paramtype"><a class="el" href="structgcm__context.html">gcm_context</a> * </td>
<td class="paramname"><em>ctx</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">int </td>
<td class="paramname"><em>mode</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">size_t </td>
<td class="paramname"><em>length</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">const unsigned char * </td>
<td class="paramname"><em>iv</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">size_t </td>
<td class="paramname"><em>iv_len</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">const unsigned char * </td>
<td class="paramname"><em>add</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">size_t </td>
<td class="paramname"><em>add_len</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">const unsigned char * </td>
<td class="paramname"><em>input</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">unsigned char * </td>
<td class="paramname"><em>output</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">size_t </td>
<td class="paramname"><em>tag_len</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">unsigned char * </td>
<td class="paramname"><em>tag</em> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
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</table>
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<p>GCM buffer encryption/decryption using a block cipher. </p>
<dl class="section note"><dt>Note</dt><dd>On encryption, the output buffer can be the same as the input buffer. On decryption, the output buffer cannot be the same as input buffer. If buffers overlap, the output buffer must trail at least 8 bytes behind the input buffer.</dd></dl>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">ctx</td><td>GCM context </td></tr>
<tr><td class="paramname">mode</td><td>GCM_ENCRYPT or GCM_DECRYPT </td></tr>
<tr><td class="paramname">length</td><td>length of the input data </td></tr>
<tr><td class="paramname">iv</td><td>initialization vector </td></tr>
<tr><td class="paramname">iv_len</td><td>length of IV </td></tr>
<tr><td class="paramname">add</td><td>additional data </td></tr>
<tr><td class="paramname">add_len</td><td>length of additional data </td></tr>
<tr><td class="paramname">input</td><td>buffer holding the input data </td></tr>
<tr><td class="paramname">output</td><td>buffer for holding the output data </td></tr>
<tr><td class="paramname">tag_len</td><td>length of the tag to generate </td></tr>
<tr><td class="paramname">tag</td><td>buffer for holding the tag</td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>0 if successful </dd></dl>
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<td class="memname">int gcm_finish </td>
<td>(</td>
<td class="paramtype"><a class="el" href="structgcm__context.html">gcm_context</a> * </td>
<td class="paramname"><em>ctx</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">unsigned char * </td>
<td class="paramname"><em>tag</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">size_t </td>
<td class="paramname"><em>tag_len</em> </td>
</tr>
<tr>
<td></td>
<td>)</td>
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<p>Generic GCM finalisation function. </p>
<p>Wraps up the GCM stream and generates the tag. The tag can have a maximum length of 16 bytes.</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">ctx</td><td>GCM context </td></tr>
<tr><td class="paramname">tag</td><td>buffer for holding the tag (may be NULL if tag_len is 0) </td></tr>
<tr><td class="paramname">tag_len</td><td>length of the tag to generate</td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>0 if successful or POLARSSL_ERR_GCM_BAD_INPUT </dd></dl>
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<td class="memname">void gcm_free </td>
<td>(</td>
<td class="paramtype"><a class="el" href="structgcm__context.html">gcm_context</a> * </td>
<td class="paramname"><em>ctx</em></td><td>)</td>
<td></td>
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<p>Free a GCM context and underlying cipher sub-context. </p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">ctx</td><td>GCM context to free </td></tr>
</table>
</dd>
</dl>
</div>
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<td class="memname">int gcm_init </td>
<td>(</td>
<td class="paramtype"><a class="el" href="structgcm__context.html">gcm_context</a> * </td>
<td class="paramname"><em>ctx</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="cipher_8h.html#a373f5d3a0a42c77ff4f5fe4fe7da0560">cipher_id_t</a> </td>
<td class="paramname"><em>cipher</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">const unsigned char * </td>
<td class="paramname"><em>key</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">unsigned int </td>
<td class="paramname"><em>keysize</em> </td>
</tr>
<tr>
<td></td>
<td>)</td>
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<p>GCM initialization (encryption) </p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">ctx</td><td>GCM context to be initialized </td></tr>
<tr><td class="paramname">cipher</td><td>cipher to use (a 128-bit block cipher) </td></tr>
<tr><td class="paramname">key</td><td>encryption key </td></tr>
<tr><td class="paramname">keysize</td><td>must be 128, 192 or 256</td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>0 if successful, or a cipher specific error code </dd></dl>
</div>
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<td class="memname">int gcm_self_test </td>
<td>(</td>
<td class="paramtype">int </td>
<td class="paramname"><em>verbose</em></td><td>)</td>
<td></td>
</tr>
</table>
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<p>Checkup routine. </p>
<dl class="section return"><dt>Returns</dt><dd>0 if successful, or 1 if the test failed </dd></dl>
</div>
</div>
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<td class="memname">int gcm_starts </td>
<td>(</td>
<td class="paramtype"><a class="el" href="structgcm__context.html">gcm_context</a> * </td>
<td class="paramname"><em>ctx</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">int </td>
<td class="paramname"><em>mode</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">const unsigned char * </td>
<td class="paramname"><em>iv</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">size_t </td>
<td class="paramname"><em>iv_len</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">const unsigned char * </td>
<td class="paramname"><em>add</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">size_t </td>
<td class="paramname"><em>add_len</em> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
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</table>
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<p>Generic GCM stream start function. </p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">ctx</td><td>GCM context </td></tr>
<tr><td class="paramname">mode</td><td>GCM_ENCRYPT or GCM_DECRYPT </td></tr>
<tr><td class="paramname">iv</td><td>initialization vector </td></tr>
<tr><td class="paramname">iv_len</td><td>length of IV </td></tr>
<tr><td class="paramname">add</td><td>additional data (or NULL if length is 0) </td></tr>
<tr><td class="paramname">add_len</td><td>length of additional data</td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>0 if successful </dd></dl>
</div>
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<td class="memname">int gcm_update </td>
<td>(</td>
<td class="paramtype"><a class="el" href="structgcm__context.html">gcm_context</a> * </td>
<td class="paramname"><em>ctx</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">size_t </td>
<td class="paramname"><em>length</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">const unsigned char * </td>
<td class="paramname"><em>input</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">unsigned char * </td>
<td class="paramname"><em>output</em> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
</tr>
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<p>Generic GCM update function. </p>
<p>Encrypts/decrypts using the given GCM context. Expects input to be a multiple of 16 bytes! Only the last call before <a class="el" href="gcm_8h.html#a6544ce0fa5390ced146b041cfa8a4f88" title="Generic GCM finalisation function. ">gcm_finish()</a> can be less than 16 bytes!</p>
<dl class="section note"><dt>Note</dt><dd>On decryption, the output buffer cannot be the same as input buffer. If buffers overlap, the output buffer must trail at least 8 bytes behind the input buffer.</dd></dl>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">ctx</td><td>GCM context </td></tr>
<tr><td class="paramname">length</td><td>length of the input data </td></tr>
<tr><td class="paramname">input</td><td>buffer holding the input data </td></tr>
<tr><td class="paramname">output</td><td>buffer for holding the output data</td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>0 if successful or POLARSSL_ERR_GCM_BAD_INPUT </dd></dl>
</div>
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