tea.cpp

// tea.cpp - modified by Wei Dai from code in the original paper

#include "pch.h"
#include "tea.h"
#include "misc.h"

NAMESPACE_BEGIN(CryptoPP)

static const word32 DELTA = 0x9e3779b9;
typedef BlockGetAndPut<word32, BigEndian> Block;

void TEA::Base::UncheckedSetKey(const byte *userKey, unsigned int length, const NameValuePairs &params)
{
        AssertValidKeyLength(length);

        GetUserKey(BIG_ENDIAN_ORDER, m_k.begin(), 4, userKey, KEYLENGTH);
        m_limit = GetRoundsAndThrowIfInvalid(params, this) * DELTA;
}

void TEA::Enc::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
        word32 y, z;
        Block::Get(inBlock)(y)(z);

        word32 sum = 0;
        while (sum != m_limit)
        {   
                sum += DELTA;
                y += (z << 4) + m_k[0] ^ z + sum ^ (z >> 5) + m_k[1];
                z += (y << 4) + m_k[2] ^ y + sum ^ (y >> 5) + m_k[3];
        }

        Block::Put(xorBlock, outBlock)(y)(z);
}

void TEA::Dec::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
        word32 y, z;
        Block::Get(inBlock)(y)(z);

        word32 sum = m_limit;
        while (sum != 0)
        {
                z -= (y << 4) + m_k[2] ^ y + sum ^ (y >> 5) + m_k[3]; 
                y -= (z << 4) + m_k[0] ^ z + sum ^ (z >> 5) + m_k[1];
                sum -= DELTA;
        }

        Block::Put(xorBlock, outBlock)(y)(z);
}

void XTEA::Base::UncheckedSetKey(const byte *userKey, unsigned int length,  const NameValuePairs &params)
{
        AssertValidKeyLength(length);

        GetUserKey(BIG_ENDIAN_ORDER, m_k.begin(), 4, userKey, KEYLENGTH);
        m_limit = GetRoundsAndThrowIfInvalid(params, this) * DELTA;
}

void XTEA::Enc::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
        word32 y, z;
        Block::Get(inBlock)(y)(z);

        word32 sum = 0;
        while (sum != m_limit)
        {   
                y += (z<<4 ^ z>>5) + z ^ sum + m_k[sum&3];
                sum += DELTA;
                z += (y<<4 ^ y>>5) + y ^ sum + m_k[sum>>11 & 3];
        }

        Block::Put(xorBlock, outBlock)(y)(z);
}

void XTEA::Dec::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
        word32 y, z;
        Block::Get(inBlock)(y)(z);

        word32 sum = m_limit;
        while (sum != 0)
        {
                z -= (y<<4 ^ y>>5) + y ^ sum + m_k[sum>>11 & 3];
                sum -= DELTA;
                y -= (z<<4 ^ z>>5) + z ^ sum + m_k[sum&3];
        }

        Block::Put(xorBlock, outBlock)(y)(z);
}

#define MX (z>>5^y<<2)+(y>>3^z<<4)^(sum^y)+(m_k[p&3^e]^z)

void BTEA::Enc::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
        unsigned int n = m_blockSize / 4;
        word32 *v = (word32*)outBlock;
        ConditionalByteReverse(BIG_ENDIAN_ORDER, v, (const word32*)inBlock, m_blockSize);

        word32 y = v[0], z = v[n-1], e;
        word32 p, q = 6+52/n;
        word32 sum = 0;
        
        while (q-- > 0)
        {   
                sum += DELTA;
                e = sum>>2 & 3;
                for (p = 0; p < n-1; p++)
                {
                        y = v[p+1];
                        z = v[p] += MX;
                }
                y = v[0];
                z = v[n-1] += MX;
        }

        ConditionalByteReverse(BIG_ENDIAN_ORDER, v, v, m_blockSize);
}

void BTEA::Dec::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
        unsigned int n = m_blockSize / 4;
        word32 *v = (word32*)outBlock;
        ConditionalByteReverse(BIG_ENDIAN_ORDER, v, (const word32*)inBlock, m_blockSize);

        word32 y = v[0], z = v[n-1], e;
        word32 p, q = 6+52/n;
        word32 sum = q * DELTA;

        while (sum != 0)
        {   
                e = sum>>2 & 3;
                for (p = n-1; p > 0; p--)
                {
                        z = v[p-1];
                        y = v[p] -= MX;
                }

                z = v[n-1];
                y = v[0] -= MX;
                sum -= DELTA;
        }

        ConditionalByteReverse(BIG_ENDIAN_ORDER, v, v, m_blockSize);
}

NAMESPACE_END

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