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122 lines
2.6 KiB
122 lines
2.6 KiB
// cmac.cpp - written and placed in the public domain by Wei Dai
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#include "pch.h"
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#ifndef CRYPTOPP_IMPORTS
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#include "cmac.h"
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NAMESPACE_BEGIN(CryptoPP)
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static void MulU(byte *k, unsigned int length)
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{
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byte carry = 0;
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for (int i=length-1; i>=1; i-=2)
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{
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byte carry2 = k[i] >> 7;
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k[i] += k[i] + carry;
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carry = k[i-1] >> 7;
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k[i-1] += k[i-1] + carry2;
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}
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if (carry)
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{
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switch (length)
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{
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case 8:
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k[7] ^= 0x1b;
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break;
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case 16:
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k[15] ^= 0x87;
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break;
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case 32:
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k[30] ^= 4;
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k[31] ^= 0x23;
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break;
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default:
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throw InvalidArgument("CMAC: " + IntToString(length) + " is not a supported cipher block size");
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}
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}
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}
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void CMAC_Base::UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs ¶ms)
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{
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BlockCipher &cipher = AccessCipher();
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unsigned int blockSize = cipher.BlockSize();
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cipher.SetKey(key, length, params);
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m_reg.CleanNew(3*blockSize);
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m_counter = 0;
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cipher.ProcessBlock(m_reg, m_reg+blockSize);
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MulU(m_reg+blockSize, blockSize);
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memcpy(m_reg+2*blockSize, m_reg+blockSize, blockSize);
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MulU(m_reg+2*blockSize, blockSize);
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}
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void CMAC_Base::Update(const byte *input, size_t length)
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{
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if (!length)
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return;
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BlockCipher &cipher = AccessCipher();
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unsigned int blockSize = cipher.BlockSize();
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if (m_counter > 0)
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{
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unsigned int len = UnsignedMin(blockSize - m_counter, length);
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xorbuf(m_reg+m_counter, input, len);
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length -= len;
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input += len;
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m_counter += len;
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if (m_counter == blockSize && length > 0)
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{
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cipher.ProcessBlock(m_reg);
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m_counter = 0;
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}
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}
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if (length > blockSize)
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{
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assert(m_counter == 0);
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size_t leftOver = 1 + cipher.AdvancedProcessBlocks(m_reg, input, m_reg, length-1, BlockTransformation::BT_DontIncrementInOutPointers|BlockTransformation::BT_XorInput);
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input += (length - leftOver);
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length = leftOver;
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}
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if (length > 0)
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{
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assert(m_counter + length <= blockSize);
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xorbuf(m_reg+m_counter, input, length);
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m_counter += (unsigned int)length;
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}
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assert(m_counter > 0);
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}
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void CMAC_Base::TruncatedFinal(byte *mac, size_t size)
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{
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ThrowIfInvalidTruncatedSize(size);
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BlockCipher &cipher = AccessCipher();
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unsigned int blockSize = cipher.BlockSize();
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if (m_counter < blockSize)
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{
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m_reg[m_counter] ^= 0x80;
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cipher.AdvancedProcessBlocks(m_reg, m_reg+2*blockSize, m_reg, blockSize, BlockTransformation::BT_DontIncrementInOutPointers|BlockTransformation::BT_XorInput);
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}
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else
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cipher.AdvancedProcessBlocks(m_reg, m_reg+blockSize, m_reg, blockSize, BlockTransformation::BT_DontIncrementInOutPointers|BlockTransformation::BT_XorInput);
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memcpy(mac, m_reg, size);
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m_counter = 0;
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memset(m_reg, 0, blockSize);
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}
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NAMESPACE_END
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#endif
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