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<h1>oaep.cpp</h1><div class="fragment"><pre class="fragment"><a name="l00001"></a>00001 <span class="comment">// oaep.cpp - written and placed in the public domain by Wei Dai</span>
<a name="l00002"></a>00002
<a name="l00003"></a>00003 <span class="preprocessor">#include "pch.h"</span>
<a name="l00004"></a>00004
<a name="l00005"></a>00005 <span class="preprocessor">#ifndef CRYPTOPP_IMPORTS</span>
<a name="l00006"></a>00006 <span class="preprocessor"></span>
<a name="l00007"></a>00007 <span class="preprocessor">#include "oaep.h"</span>
<a name="l00008"></a>00008 <span class="preprocessor">#include <functional></span>
<a name="l00009"></a>00009
<a name="l00010"></a>00010 NAMESPACE_BEGIN(CryptoPP)
<a name="l00011"></a>00011
<a name="l00012"></a>00012 <span class="comment">// ********************************************************</span>
<a name="l00013"></a>00013
<a name="l00014"></a><a class="code" href="class_o_a_e_p___base.html#a1ed015fe85be14a49d5f1fd8216fbef8">00014</a> size_t <a class="code" href="class_o_a_e_p___base.html" title="_">OAEP_Base</a>::MaxUnpaddedLength(<span class="keywordtype">size_t</span> paddedLength)<span class="keyword"> const</span>
<a name="l00015"></a>00015 <span class="keyword"></span>{
<a name="l00016"></a>00016 <span class="keywordflow">return</span> SaturatingSubtract(paddedLength/8, 1+2*DigestSize());
<a name="l00017"></a>00017 }
<a name="l00018"></a>00018
<a name="l00019"></a>00019 <span class="keywordtype">void</span> OAEP_Base::Pad(<a class="code" href="class_random_number_generator.html" title="interface for random number generators">RandomNumberGenerator</a> &rng, <span class="keyword">const</span> byte *input, <span class="keywordtype">size_t</span> inputLength, byte *oaepBlock, <span class="keywordtype">size_t</span> oaepBlockLen, <span class="keyword">const</span> <a class="code" href="class_name_value_pairs.html" title="interface for retrieving values given their names">NameValuePairs</a> &parameters)<span class="keyword"> const</span>
<a name="l00020"></a>00020 <span class="keyword"></span>{
<a name="l00021"></a>00021 assert (inputLength <= <a class="code" href="class_o_a_e_p___base.html#a1ed015fe85be14a49d5f1fd8216fbef8" title="max size of unpadded message in bytes, given max size of padded message in bits (1...">MaxUnpaddedLength</a>(oaepBlockLen));
<a name="l00022"></a>00022
<a name="l00023"></a>00023 <span class="comment">// convert from bit length to byte length</span>
<a name="l00024"></a>00024 <span class="keywordflow">if</span> (oaepBlockLen % 8 != 0)
<a name="l00025"></a>00025 {
<a name="l00026"></a>00026 oaepBlock[0] = 0;
<a name="l00027"></a>00027 oaepBlock++;
<a name="l00028"></a>00028 }
<a name="l00029"></a>00029 oaepBlockLen /= 8;
<a name="l00030"></a>00030
<a name="l00031"></a>00031 std::auto_ptr<HashTransformation> pHash(NewHash());
<a name="l00032"></a>00032 <span class="keyword">const</span> <span class="keywordtype">size_t</span> hLen = pHash->DigestSize();
<a name="l00033"></a>00033 <span class="keyword">const</span> <span class="keywordtype">size_t</span> seedLen = hLen, dbLen = oaepBlockLen-seedLen;
<a name="l00034"></a>00034 byte *<span class="keyword">const</span> maskedSeed = oaepBlock;
<a name="l00035"></a>00035 byte *<span class="keyword">const</span> maskedDB = oaepBlock+seedLen;
<a name="l00036"></a>00036
<a name="l00037"></a>00037 <a class="code" href="class_const_byte_array_parameter.html" title="used to pass byte array input as part of a NameValuePairs object">ConstByteArrayParameter</a> encodingParameters;
<a name="l00038"></a>00038 parameters.<a class="code" href="class_name_value_pairs.html#a96686e9f8d6ce3ab870e516fb72b608e" title="get a named value, returns true if the name exists">GetValue</a>(Name::EncodingParameters(), encodingParameters);
<a name="l00039"></a>00039
<a name="l00040"></a>00040 <span class="comment">// DB = pHash || 00 ... || 01 || M</span>
<a name="l00041"></a>00041 pHash->CalculateDigest(maskedDB, encodingParameters.begin(), encodingParameters.size());
<a name="l00042"></a>00042 memset(maskedDB+hLen, 0, dbLen-hLen-inputLength-1);
<a name="l00043"></a>00043 maskedDB[dbLen-inputLength-1] = 0x01;
<a name="l00044"></a>00044 memcpy(maskedDB+dbLen-inputLength, input, inputLength);
<a name="l00045"></a>00045
<a name="l00046"></a>00046 rng.<a class="code" href="class_random_number_generator.html#a497145546d24e6d4abaf10b7e0f1ba17" title="generate random array of bytes">GenerateBlock</a>(maskedSeed, seedLen);
<a name="l00047"></a>00047 std::auto_ptr<MaskGeneratingFunction> pMGF(NewMGF());
<a name="l00048"></a>00048 pMGF->GenerateAndMask(*pHash, maskedDB, dbLen, maskedSeed, seedLen);
<a name="l00049"></a>00049 pMGF->GenerateAndMask(*pHash, maskedSeed, seedLen, maskedDB, dbLen);
<a name="l00050"></a>00050 }
<a name="l00051"></a>00051
<a name="l00052"></a>00052 <a class="code" href="struct_decoding_result.html" title="used to return decoding results">DecodingResult</a> OAEP_Base::Unpad(<span class="keyword">const</span> byte *oaepBlock, <span class="keywordtype">size_t</span> oaepBlockLen, byte *output, <span class="keyword">const</span> <a class="code" href="class_name_value_pairs.html" title="interface for retrieving values given their names">NameValuePairs</a> &parameters)<span class="keyword"> const</span>
<a name="l00053"></a>00053 <span class="keyword"></span>{
<a name="l00054"></a>00054 <span class="keywordtype">bool</span> invalid = <span class="keyword">false</span>;
<a name="l00055"></a>00055
<a name="l00056"></a>00056 <span class="comment">// convert from bit length to byte length</span>
<a name="l00057"></a>00057 <span class="keywordflow">if</span> (oaepBlockLen % 8 != 0)
<a name="l00058"></a>00058 {
<a name="l00059"></a>00059 invalid = (oaepBlock[0] != 0) || invalid;
<a name="l00060"></a>00060 oaepBlock++;
<a name="l00061"></a>00061 }
<a name="l00062"></a>00062 oaepBlockLen /= 8;
<a name="l00063"></a>00063
<a name="l00064"></a>00064 std::auto_ptr<HashTransformation> pHash(NewHash());
<a name="l00065"></a>00065 <span class="keyword">const</span> <span class="keywordtype">size_t</span> hLen = pHash->DigestSize();
<a name="l00066"></a>00066 <span class="keyword">const</span> <span class="keywordtype">size_t</span> seedLen = hLen, dbLen = oaepBlockLen-seedLen;
<a name="l00067"></a>00067
<a name="l00068"></a>00068 invalid = (oaepBlockLen < 2*hLen+1) || invalid;
<a name="l00069"></a>00069
<a name="l00070"></a>00070 <a class="code" href="class_sec_block.html" title="a block of memory allocated using A">SecByteBlock</a> t(oaepBlock, oaepBlockLen);
<a name="l00071"></a>00071 byte *<span class="keyword">const</span> maskedSeed = t;
<a name="l00072"></a>00072 byte *<span class="keyword">const</span> maskedDB = t+seedLen;
<a name="l00073"></a>00073
<a name="l00074"></a>00074 std::auto_ptr<MaskGeneratingFunction> pMGF(NewMGF());
<a name="l00075"></a>00075 pMGF->GenerateAndMask(*pHash, maskedSeed, seedLen, maskedDB, dbLen);
<a name="l00076"></a>00076 pMGF->GenerateAndMask(*pHash, maskedDB, dbLen, maskedSeed, seedLen);
<a name="l00077"></a>00077
<a name="l00078"></a>00078 <a class="code" href="class_const_byte_array_parameter.html" title="used to pass byte array input as part of a NameValuePairs object">ConstByteArrayParameter</a> encodingParameters;
<a name="l00079"></a>00079 parameters.<a class="code" href="class_name_value_pairs.html#a96686e9f8d6ce3ab870e516fb72b608e" title="get a named value, returns true if the name exists">GetValue</a>(Name::EncodingParameters(), encodingParameters);
<a name="l00080"></a>00080
<a name="l00081"></a>00081 <span class="comment">// DB = pHash' || 00 ... || 01 || M</span>
<a name="l00082"></a>00082 byte *M = std::find(maskedDB+hLen, maskedDB+dbLen, 0x01);
<a name="l00083"></a>00083 invalid = (M == maskedDB+dbLen) || invalid;
<a name="l00084"></a>00084 invalid = (std::find_if(maskedDB+hLen, M, std::bind2nd(std::not_equal_to<byte>(), 0)) != M) || invalid;
<a name="l00085"></a>00085 invalid = !pHash->VerifyDigest(maskedDB, encodingParameters.begin(), encodingParameters.size()) || invalid;
<a name="l00086"></a>00086
<a name="l00087"></a>00087 <span class="keywordflow">if</span> (invalid)
<a name="l00088"></a>00088 <span class="keywordflow">return</span> <a class="code" href="struct_decoding_result.html" title="used to return decoding results">DecodingResult</a>();
<a name="l00089"></a>00089
<a name="l00090"></a>00090 M++;
<a name="l00091"></a>00091 memcpy(output, M, maskedDB+dbLen-M);
<a name="l00092"></a>00092 <span class="keywordflow">return</span> <a class="code" href="struct_decoding_result.html" title="used to return decoding results">DecodingResult</a>(maskedDB+dbLen-M);
<a name="l00093"></a>00093 }
<a name="l00094"></a>00094
<a name="l00095"></a>00095 NAMESPACE_END
<a name="l00096"></a>00096
<a name="l00097"></a>00097 <span class="preprocessor">#endif</span>
</pre></div></div>
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