/*

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   888 8K  d888 888bd888 8Shaoziyang88d888 888b"8" 888d888 888d88 88b888 "
   888 88b,Y888 888PY888 888P 888  888Y888 888P,ee 888Y888 888888   ,888
   888 88P' "88 88"  "88 88"  888  888 "88 88" "88 888 "88 888 "YeeP"888


  Project:       AVR 通用 BootLoader
  File:          pc1crypt.c
                 PC1 加密算法( Pukall Cipher 1 ) 源自 "http://membres.lycos.fr/pc1/"
                 128/256 位密鑰
                 為 avr 8 位單片機進行了優化
  Version:       1.2

  Compiler:      WinAVR 20071221 + AVR Studio 4.14.589

  Author:        Shaoziyang
                 Shaoziyang@gmail.com
                 http://avrubd.googlepages.com
                 http://groups.google.com/group/avrub?hl=en
                 
  Date:          2008.6

  See readme.htm to get more information.

*/


#ifndef PC1_128
#define PC1_128   1
#endif

#ifndef PC1_256
#define PC1_256   2
#endif

#ifndef Algorithm
#define Algorithm PC1_128
#endif

unsigned int ax, bx, cx, dx, inter, cfc, cfd;
unsigned int si, x1a2;

#if (Algorithm == PC1_128)
unsigned int x1a0[9];
#elif  (Algorithm == PC1_256)
unsigned int x1a0[17];
#else
#error "Unknow encrypt algorithm!"
#endif

#define DecryptInit()                                                     \
        {                                                                 \
                           si = 0;                                        \
                           x1a2 = 0;                                      \
        }

void exchange(unsigned int *a, unsigned int *b)
{
  unsigned int tmp;

  tmp = *a;
  *a = *b;
  *b = tmp;
}

#if (Algorithm == PC1_128)
void PC1assemble128()
{
  unsigned char i;

  inter = 0;
  x1a0[0] = 0;
  for(i = 0; i < 8; i++)
  {
    x1a0[i + 1] = x1a0[i] ^ ((DecryptKey[i * 2] * 256) + DecryptKey[i * 2 + 1]);

    dx = x1a2 + i;
    ax = x1a0[i + 1];
    cx = 0x015A;
    bx = 0x4E35;

    exchange(&ax, &si);
    exchange(&ax, &dx);

    if (ax != 0)
    {
      ax = ax * bx;
    }

    exchange(&ax, &cx);

    if (ax != 0)
    {
      ax = ax * si;
      cx = ax + cx;
    }

    exchange(&ax, &si);

    ax = ax * bx;
    dx = cx + dx;
    ax = ax + 1;

    x1a2 = dx;
    x1a0[i + 1] = ax;

    inter = inter ^ (ax ^ dx);
  }
}

//解密一個字節
unsigned char PC1Dec128Byte(unsigned char c)
{
  unsigned char i;

  PC1assemble128();
  cfc = inter >> 8;
  cfd = inter & 255;
  c = c ^ (cfc ^ cfd);

  for(i = 0; i < 16; i++)
    DecryptKey[i] = DecryptKey[i] ^ c;

  return c;
}

#endif //PC1_128

#if (Algorithm == PC1_256)
void PC1assemble256()
{
  unsigned char i;

  inter = 0;
  x1a0[0] = 0;
  for(i = 0; i < 16; i++)
  {
    x1a0[i + 1] = x1a0[i] ^ ((DecryptKey[i * 2] * 256) + DecryptKey[i * 2 + 1]);

    dx = x1a2 + i;
    ax = x1a0[i + 1];
    cx = 0x015A;
    bx = 0x4E35;

    exchange(&ax, &si);
    exchange(&ax, &dx);

    if (ax != 0)
    {
      ax = ax * bx;
    }

    exchange(&ax, &cx);

    if (ax != 0)
    {
      ax = ax * si;
      cx = ax + cx;
    }

    exchange(&ax, &si);

    ax = ax * bx;
    dx = cx + dx;
    ax = ax + 1;

    x1a2 = dx;
    x1a0[i + 1] = ax;

    inter = inter ^ (ax ^ dx);
  }
}

//解密一個字節
unsigned char PC1Dec256Byte(unsigned char c)
{
  unsigned char i;

  PC1assemble256();
  cfc = inter >> 8;
  cfd = inter & 255;
  c = c ^ (cfc ^ cfd);

  for(i = 0; i < 32; i++)
    DecryptKey[i] = DecryptKey[i] ^ c;

  return c;
}

#endif //PC1_256

//解密數據塊
void DecryptBlock(unsigned char *buf, unsigned int nSize)
{
  unsigned int n;

  for( n = nSize; n > 0; n--)
  {
#if (Algorithm == PC1_128)
    *buf = PC1Dec128Byte(*buf);
#else
    *buf = PC1Dec256Byte(*buf);
#endif
    buf++;
  }
}

//銷毀密鑰
void DestroyKey()
{
  unsigned char i;

#if (Algorithm == PC1_128)
  for(i = 0; i < 16; i++)
#else
  for(i = 0; i < 32; i++)
#endif
  {
    DecryptKey[i] = 0;
  }
}

//end of file