pkcspad_8cpp-source.html

著名的密码库Crypto++的文档 C++语言的杰作。程序员必备。

<a name="l00056"></a>00056         <span class="keywordtype">size_t</span> maxOutputLen = <a class="code" href="class_p_k_c_s___encryption_padding_scheme.html#9a747d8f4b5b30b2569e8f717a544d8d" title="max size of unpadded message in bytes, given max size of padded message in bits (1...">MaxUnpaddedLength</a>(pkcsBlockLen);
<a name="l00057"></a>00057 
<a name="l00058"></a>00058         <span class="comment">// convert from bit length to byte length</span>
<a name="l00059"></a>00059         <span class="keywordflow">if</span> (pkcsBlockLen % 8 != 0)
<a name="l00060"></a>00060         {
<a name="l00061"></a>00061                 invalid = (pkcsBlock[0] != 0) || invalid;
<a name="l00062"></a>00062                 pkcsBlock++;
<a name="l00063"></a>00063         }
<a name="l00064"></a>00064         pkcsBlockLen /= 8;
<a name="l00065"></a>00065 
<a name="l00066"></a>00066         <span class="comment">// Require block type 2.</span>
<a name="l00067"></a>00067         invalid = (pkcsBlock[0] != 2) || invalid;
<a name="l00068"></a>00068 
<a name="l00069"></a>00069         <span class="comment">// skip past the padding until we find the separator</span>
<a name="l00070"></a>00070         <span class="keywordtype">size_t</span> i=1;
<a name="l00071"></a>00071         <span class="keywordflow">while</span> (i&lt;pkcsBlockLen &amp;&amp; pkcsBlock[i++]) { <span class="comment">// null body</span>
<a name="l00072"></a>00072                 }
<a name="l00073"></a>00073         assert(i==pkcsBlockLen || pkcsBlock[i-1]==0);
<a name="l00074"></a>00074 
<a name="l00075"></a>00075         <span class="keywordtype">size_t</span> outputLen = pkcsBlockLen - i;
<a name="l00076"></a>00076         invalid = (outputLen &gt; maxOutputLen) || invalid;
<a name="l00077"></a>00077 
<a name="l00078"></a>00078         <span class="keywordflow">if</span> (invalid)
<a name="l00079"></a>00079                 <span class="keywordflow">return</span> <a class="code" href="struct_decoding_result.html" title="used to return decoding results">DecodingResult</a>();
<a name="l00080"></a>00080 
<a name="l00081"></a>00081         memcpy (output, pkcsBlock+i, outputLen);
<a name="l00082"></a>00082         <span class="keywordflow">return</span> <a class="code" href="struct_decoding_result.html" title="used to return decoding results">DecodingResult</a>(outputLen);
<a name="l00083"></a>00083 }
<a name="l00084"></a>00084 
<a name="l00085"></a>00085 <span class="comment">// ********************************************************</span>
<a name="l00086"></a>00086 
<a name="l00087"></a>00087 <span class="preprocessor">#ifndef CRYPTOPP_IMPORTS</span>
<a name="l00088"></a>00088 <span class="preprocessor"></span>
<a name="l00089"></a><a class="code" href="class_p_k_c_s1v15___signature_message_encoding_method.html#526cc56a45c9a866391e437ea292900e">00089</a> <span class="keywordtype">void</span> <a class="code" href="class_p_k_c_s1v15___signature_message_encoding_method.html#526cc56a45c9a866391e437ea292900e">PKCS1v15_SignatureMessageEncodingMethod::ComputeMessageRepresentative</a>(<a class="code" href="class_random_number_generator.html" title="interface for random number generators">RandomNumberGenerator</a> &amp;rng, 
<a name="l00090"></a>00090         <span class="keyword">const</span> byte *recoverableMessage, <span class="keywordtype">size_t</span> recoverableMessageLength,
<a name="l00091"></a>00091         <a class="code" href="class_hash_transformation.html" title="interface for hash functions and data processing part of MACs">HashTransformation</a> &amp;hash, <a class="code" href="pubkey_8h.html#ef874ed3f2d212ac4629255c8ef86dd0">HashIdentifier</a> hashIdentifier, <span class="keywordtype">bool</span> messageEmpty,
<a name="l00092"></a>00092         byte *representative, <span class="keywordtype">size_t</span> representativeBitLength)<span class="keyword"> const</span>
<a name="l00093"></a>00093 <span class="keyword"></span>{
<a name="l00094"></a>00094         assert(representativeBitLength &gt;= <a class="code" href="class_p_k_c_s1v15___signature_message_encoding_method.html#3aaceb7647075b30272f8d48cb28ec54">MinRepresentativeBitLength</a>(hashIdentifier.second, hash.<a class="code" href="class_hash_transformation.html#41faf8b1293a6c72390cb0c8bd668097" title="size of the hash returned by Final()">DigestSize</a>()));
<a name="l00095"></a>00095 
<a name="l00096"></a>00096         <span class="keywordtype">size_t</span> pkcsBlockLen = representativeBitLength;
<a name="l00097"></a>00097         <span class="comment">// convert from bit length to byte length</span>
<a name="l00098"></a>00098         <span class="keywordflow">if</span> (pkcsBlockLen % 8 != 0)
<a name="l00099"></a>00099         {
<a name="l00100"></a>00100                 representative[0] = 0;
<a name="l00101"></a>00101                 representative++;
<a name="l00102"></a>00102         }
<a name="l00103"></a>00103         pkcsBlockLen /= 8;
<a name="l00104"></a>00104 
<a name="l00105"></a>00105         representative[0] = 1;   <span class="comment">// block type 1</span>
<a name="l00106"></a>00106 
<a name="l00107"></a>00107         <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> digestSize = hash.<a class="code" href="class_hash_transformation.html#41faf8b1293a6c72390cb0c8bd668097" title="size of the hash returned by Final()">DigestSize</a>();
<a name="l00108"></a>00108         byte *pPadding = representative + 1;
<a name="l00109"></a>00109         byte *pDigest = representative + pkcsBlockLen - digestSize;
<a name="l00110"></a>00110         byte *pHashId = pDigest - hashIdentifier.second;
<a name="l00111"></a>00111         byte *pSeparator = pHashId - 1;
<a name="l00112"></a>00112 
<a name="l00113"></a>00113         <span class="comment">// pad with 0xff</span>
<a name="l00114"></a>00114         memset(pPadding, 0xff, pSeparator-pPadding);
<a name="l00115"></a>00115         *pSeparator = 0;
<a name="l00116"></a>00116         memcpy(pHashId, hashIdentifier.first, hashIdentifier.second);
<a name="l00117"></a>00117         hash.<a class="code" href="class_hash_transformation.html#a0b8c7a110d8968268fd02ec32b9a8e8" title="compute hash for current message, then restart for a new message">Final</a>(pDigest);
<a name="l00118"></a>00118 }
<a name="l00119"></a>00119 
<a name="l00120"></a>00120 <span class="preprocessor">#endif</span>
<a name="l00121"></a>00121 <span class="preprocessor"></span>
<a name="l00122"></a>00122 NAMESPACE_END
<a name="l00123"></a>00123 
<a name="l00124"></a>00124 <span class="preprocessor">#endif</span>
</pre></div><hr size="1"><address style="text-align: right;"><small>Generated on Fri Jun 1 11:11:23 2007 for Crypto++ by&nbsp;
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