eax.cpp

// eax.cpp - 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();

        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()
{
        assert(m_bufferedDataLength == 0);
        MessageAuthenticationCode &mac = AccessMAC();
        unsigned int blockSize = mac.TagSize();

        mac.Final(m_buffer);
        xorbuf(m_buffer+blockSize, m_buffer, blockSize);

        memset(m_buffer, 0, blockSize);
        m_buffer[blockSize-1] = 2;
        mac.Update(m_buffer, blockSize);
}

void EAX_Base::AuthenticateLastFooterBlock(byte *tag, size_t macSize)
{
        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