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// eax.cpp - originally written and placed in the public domain by Wei Dai
#include "pch.h"
#include "eax.h"
NAMESPACE_BEGIN(CryptoPP)
void EAX_Base::SetKeyWithoutResync(const byte *userKey, size_t keylength, const NameValuePairs ¶ms)
{
AccessMAC().SetKey(userKey, keylength, params);
m_buffer.New(2*AccessMAC().TagSize());
}
void EAX_Base::Resync(const byte *iv, size_t len)
{
MessageAuthenticationCode &mac = AccessMAC();
unsigned int blockSize = mac.TagSize();
std::memset(m_buffer, 0, blockSize);
mac.Update(m_buffer, blockSize);
mac.CalculateDigest(m_buffer+blockSize, iv, len);
m_buffer[blockSize-1] = 1;
mac.Update(m_buffer, blockSize);
m_ctr.SetCipherWithIV(AccessMAC().AccessCipher(), m_buffer+blockSize, blockSize);
}
size_t EAX_Base::AuthenticateBlocks(const byte *data, size_t len)
{
AccessMAC().Update(data, len);
return 0;
}
void EAX_Base::AuthenticateLastHeaderBlock()
{
CRYPTOPP_ASSERT(m_bufferedDataLength == 0);
MessageAuthenticationCode &mac = AccessMAC();
const unsigned int blockSize = mac.TagSize();
mac.Final(m_buffer);
xorbuf(m_buffer+blockSize, m_buffer, blockSize);
std::memset(m_buffer, 0, blockSize);
m_buffer[blockSize-1] = 2;
mac.Update(m_buffer, blockSize);
}
void EAX_Base::AuthenticateLastFooterBlock(byte *tag, size_t macSize)
{
CRYPTOPP_ASSERT(m_bufferedDataLength == 0);
MessageAuthenticationCode &mac = AccessMAC();
unsigned int blockSize = mac.TagSize();
mac.TruncatedFinal(m_buffer, macSize);
xorbuf(tag, m_buffer, m_buffer+blockSize, macSize);
}
NAMESPACE_END
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