eax.cpp

// 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 &params)
{
    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