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# pkcspad.cpp

    00001 // pkcspad.cpp - written and placed in the public domain by Wei Dai
    00002
    00003 #include "pch.h"
    00004
    00005 #include "pkcspad.h"
    00006 #include <assert.h>
    00007
    00008 NAMESPACE_BEGIN(CryptoPP)
    00009
    00010 // more in dll.cpp
    00011 template<> const byte PKCS_DigestDecoration<MD2>::decoration[] = {0x30,0x20,0x30,0x0c,0x06,0x08,0x2a,0x86,0x48,0x86,0xf7,0x0d,0x02,0x02,0x05,0x00,0x04,0x10};
    00012 template<> const unsigned int PKCS_DigestDecoration<MD2>::length = sizeof(PKCS_DigestDecoration<MD2>::decoration);
    00013
    00014 template<> const byte PKCS_DigestDecoration<MD5>::decoration[] = {0x30,0x20,0x30,0x0c,0x06,0x08,0x2a,0x86,0x48,0x86,0xf7,0x0d,0x02,0x05,0x05,0x00,0x04,0x10};
    00015 template<> const unsigned int PKCS_DigestDecoration<MD5>::length = sizeof(PKCS_DigestDecoration<MD5>::decoration);
    00016
    00017 template<> const byte PKCS_DigestDecoration<RIPEMD160>::decoration[] = {0x30,0x21,0x30,0x09,0x06,0x05,0x2b,0x24,0x03,0x02,0x01,0x05,0x00,0x04,0x14};
    00018 template<> const unsigned int PKCS_DigestDecoration<RIPEMD160>::length = sizeof(PKCS_DigestDecoration<RIPEMD160>::decoration);
    00019
    00020 template<> const byte PKCS_DigestDecoration<Tiger>::decoration[] = {0x30,0x29,0x30,0x0D,0x06,0x09,0x2B,0x06,0x01,0x04,0x01,0xDA,0x47,0x0C,0x02,0x05,0x00,0x04,0x18};
    00021 template<> const unsigned int PKCS_DigestDecoration<Tiger>::length = sizeof(PKCS_DigestDecoration<Tiger>::decoration);
    00022
    00023 size_t PKCS_EncryptionPaddingScheme::MaxUnpaddedLength(size_t paddedLength) const
    00024 {
    00025         return SaturatingSubtract(paddedLength/8, 10U);
    00026 }
    00027
    00028 void PKCS_EncryptionPaddingScheme::Pad(RandomNumberGenerator &rng, const byte *input, size_t inputLen, byte *pkcsBlock, size_t pkcsBlockLen, const NameValuePairs &parameters) const
    00029 {
    00030         assert (inputLen <= MaxUnpaddedLength(pkcsBlockLen));   // this should be checked by caller
    00031
    00032         // convert from bit length to byte length
    00033         if (pkcsBlockLen % 8 != 0)
    00034         {
    00035                 pkcsBlock[0] = 0;
    00036                 pkcsBlock++;
    00037         }
    00038         pkcsBlockLen /= 8;
    00039
    00040         pkcsBlock[0] = 2;  // block type 2
    00041
    00042         // pad with non-zero random bytes
    00043         for (unsigned i = 1; i < pkcsBlockLen-inputLen-1; i++)
    00044                 pkcsBlock[i] = (byte)rng.GenerateWord32(1, 0xff);
    00045
    00046         pkcsBlock[pkcsBlockLen-inputLen-1] = 0;     // separator
    00047         memcpy(pkcsBlock+pkcsBlockLen-inputLen, input, inputLen);
    00048 }
    00049
    00050 DecodingResult PKCS_EncryptionPaddingScheme::Unpad(const byte *pkcsBlock, size_t pkcsBlockLen, byte *output, const NameValuePairs &parameters) const
    00051 {
    00052         bool invalid = false;
    00053         size_t maxOutputLen = MaxUnpaddedLength(pkcsBlockLen);
    00054
    00055         // convert from bit length to byte length
    00056         if (pkcsBlockLen % 8 != 0)
    00057         {
    00058                 invalid = (pkcsBlock[0] != 0) || invalid;
    00059                 pkcsBlock++;
    00060         }
    00061         pkcsBlockLen /= 8;
    00062
    00063         // Require block type 2.
    00064         invalid = (pkcsBlock[0] != 2) || invalid;
    00065
    00066         // skip past the padding until we find the separator
    00067         size_t i=1;
    00068         while (i<pkcsBlockLen && pkcsBlock[i++]) { // null body
    00069                 }
    00070         assert(i==pkcsBlockLen || pkcsBlock[i-1]==0);
    00071
    00072         size_t outputLen = pkcsBlockLen - i;
    00073         invalid = (outputLen > maxOutputLen) || invalid;
    00074
    00075         if (invalid)
    00076                 return DecodingResult();
    00077
    00078         memcpy (output, pkcsBlock+i, outputLen);
    00079         return DecodingResult(outputLen);
    00080 }
    00081
    00082 // ********************************************************
    00083
    00084 #ifndef CRYPTOPP_IMPORTS
    00085
    00086 void PKCS1v15_SignatureMessageEncodingMethod::ComputeMessageRepresentative(RandomNumberGenerator &rng,
    00087         const byte *recoverableMessage, size_t recoverableMessageLength,
    00088         HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
    00089         byte *representative, size_t representativeBitLength) const
    00090 {
    00091         assert(representativeBitLength >= MinRepresentativeBitLength(hashIdentifier.second, hash.DigestSize()));
    00092
    00093         size_t pkcsBlockLen = representativeBitLength;
    00094         // convert from bit length to byte length
    00095         if (pkcsBlockLen % 8 != 0)
    00096         {
    00097                 representative[0] = 0;
    00098                 representative++;
    00099         }
    00100         pkcsBlockLen /= 8;
    00101
    00102         representative[0] = 1;   // block type 1
    00103
    00104         unsigned int digestSize = hash.DigestSize();
    00105         byte *pPadding = representative + 1;
    00106         byte *pDigest = representative + pkcsBlockLen - digestSize;
    00107         byte *pHashId = pDigest - hashIdentifier.second;
    00108         byte *pSeparator = pHashId - 1;
    00109
    00110         // pad with 0xff
    00111         memset(pPadding, 0xff, pSeparator-pPadding);
    00112         *pSeparator = 0;
    00113         memcpy(pHashId, hashIdentifier.first, hashIdentifier.second);
    00114         hash.Final(pDigest);
    00115 }
    00116
    00117 #endif
    00118
    00119 NAMESPACE_END