// RC5.cpp : 定義控制臺應用程序的入口點。
#include <stdio.h>
#include <string.h>
#include <math.h>
//此程序為RC5加密算法的實現--參數32/12/16
int is_Destpathright(char *dest_path);
int is_Sourcepathright(char *source_path);
int Check(int argc,char **argv);
int Encrpt(char *sourcepath,char *destpath,char *key);
int Decrypt(char *sourcepath,char *destpath,char *key);
int main(int argc,char **argv)
{
 if (Check(argc,argv)==0){
  return -1;
 }
 if (argv[4][0]=='e'||argv[4][0]=='E'){
  if(Encrpt(argv[1],argv[2],argv[3]))
   return 1;
  else
   return -1;
 }
 if (argv[4][0]=='d'||argv[4][0]=='D'){
  if(Decrypt(argv[1],argv[2],argv[3]))
   return 1;
  else
   return -1;
 }
 return -1;
}
int is_Sourcepathright(char *source_path)
{
 FILE *fp;
 if ((fp=fopen(source_path,"rb"))==NULL){
  printf("您所輸入的文件不存在.");
  fclose(fp);
  return 0;
 }
 else{
  fclose(fp);
  return 1;
 }
}
int is_Destpathright(char *dest_path)
{
 FILE *fp;
 if ((fp=fopen(dest_path,"wb"))==NULL){
  printf("輸入的路徑不正確.");
  fclose(fp);
  return 0;
 }
 else{
  fclose(fp);
  return 1;
 }
}
int is_InputKeyRight(char *inputkey)
{
 if(strlen(inputkey)==16)
  return 1;
 else
  return 0;
}
int Check(int argc,char **argv)
{
 if(argc!=5){
  printf("命令長度有錯誤。\n");
  return 0;
 }
 if(is_Sourcepathright(argv[1])==0){
  return 0;
 }
 if(is_Destpathright(argv[2])==0){
  return 0;
 }
 if(is_InputKeyRight(argv[3])==0){
  printf("輸入的密鑰不正確。\n");
  return 0;
 }
 if(strlen(argv[4])>1){
  printf("錯誤的加解密類型。\n");
  return 0;
 }
 if(argv[4][0]!='e'&&argv[4][0]!='E'&&argv[4][0]!='d'&&argv[4][0]!='D'){
  printf("錯誤的加解密類型。\n");
  return 0;
 }
 return 1;
}
int ls(unsigned int input,int nbit)
{
 unsigned int temp;
 temp=input;
 if(nbit%32==0)
  return input;
 nbit=nbit%32;
 input<<=nbit;
 temp>>=(32-nbit);
 return input+temp;
}
int rs(unsigned int input,int nbit)
{
 unsigned int temp;
 temp=input;
 if(nbit%32==0)
  return input;
 nbit=nbit%32;
 input>>=nbit;
 temp<<=(32-nbit);
 return input+temp;
}

//產生子鑰
void Key_Ger(unsigned int *sk,char *key)
{
 int i,j,x,y;
 int l[4]={0};
 int times;
 sk[0]=0xB7E15163;
 for(i=1;i<=25;i++)
  sk[i]=(sk[i-1]+0x9E3779B9);
 for(i=0;i<4;i++){
  l[i]+=key[0+i*4];
  l[i]<<=8;
  l[i]+=key[1+i*4];
  l[i]<<=8;
  l[i]+=key[2+i*4];
  l[i]<<=8;
  l[i]+=key[3+i*4];
 }
 i=j=x=y=0;
 for(times=0;times<78;times++){
  sk[i]=ls((sk[i]+x+y),3);
  x=sk[i];
  i=(i+1)%26;
  l[j]=ls((l[j]+x+y),x+y);
  y=l[j];
  j=(j+1)%4;
 }
}
//加密函數
void rc5crypt(unsigned char *buf,unsigned char *output,int *sk)
{
 int i;
 unsigned int a=0,b=0;
 unsigned int left0=0,left1=0,right0=0,right1=0;
 a+=buf[0];
 a<<=8;
 a+=buf[1];
 a<<=8;
 a+=buf[2];
 a<<=8;
 a+=buf[3];
 b+=buf[4];
 b<<=8;
 b+=buf[5];
 b<<=8;
 b+=buf[6];
 b<<=8;
 b+=buf[7];
 left0=a+sk[0];
 right0=b+sk[1];
 for(i=1;i<=12;i++){
  left1=(ls(left0^right0,right0)+sk[2*i]);
  right1=(ls(right0^left1,left1)+sk[2*i+1]);
  left0=left1;
  right0=right1;
 }
 for(i=0;i<8;i++)
  output[i]=0;
 output[0]=(left0>>24)&0xFF;
 output[1]=(left0>>16)&0xFF;
 output[2]=(left0>>8)&0xFF;
 output[3]=(left0>>0)&0xFF;
 output[4]=(right0>>24)&0xFF;
 output[5]=(right0>>16)&0xFF;
 output[6]=(right0>>8)&0xFF;
 output[7]=(right0>>0)&0xFF;
}
//解密函數
void rc5decrypt(unsigned char *buf,unsigned char *output,int *sk)
{
 unsigned int left0=0,left1=0,right0=0,right1=0;
 unsigned int a=0,b=0;
 int i;
  left1=buf[0];
  left1<<=8;
  left1+=buf[1];
  left1<<=8;
  left1+=buf[2];
  left1<<=8;
  left1+=buf[3];
  right1+=buf[4];
  right1<<=8;
  right1+=buf[5];
  right1<<=8;
  right1+=buf[6];
  right1<<=8;
  right1+=buf[7];
  for(i=12;i>=1;i--){
   right0=(rs(right1-sk[2*i+1],left1)^left1);
   left0=(rs(left1-sk[2*i],right0)^right0);
   left1=left0;
   right1=right0;
  }
  b=right0-sk[1];
  a=left0-sk[0];
  for(i=0;i<8;i++)
   output[i]=0;
  output[0]=(a>>24)&0xFF;
  output[1]=(a>>16)&0xFF;
  output[2]=(a>>8)&0xFF;
  output[3]=(a>>0)&0xFF;
  output[4]=(b>>24)&0xFF;
  output[5]=(b>>16)&0xFF;
  output[6]=(b>>8)&0xFF;
  output[7]=(b>>0)&0xFF;
}
int Encrpt(char *sourcepath,char *destpath,char *key)
{
 unsigned int sk[26]={0};
 Key_Ger(sk,key);
 FILE *fsource;
 FILE *fdest;
 int i;
 int filesize=0;
 int crypttimes=0;
 unsigned char buf[8]={0};
 unsigned char output[8]={0};
 fsource=fopen(sourcepath,"rb");
 fdest=fopen(destpath,"wb");
 fseek(fsource,0,2);
 filesize=ftell(fsource);
 rewind(fsource);
 crypttimes=filesize/8;
 while(crypttimes>0){
  for(i=0;i<8;i++)
   buf[i]=fgetc(fsource);
  rc5crypt(buf,output,sk);
  for(i=0;i<8;i++)
   fputc(output[i],fdest);
  crypttimes--;
 }
 if(filesize%8!=0){
  for(i=0;i<filesize%8;i++)
   buf[i]=fgetc(fsource);
  for(i=filesize%8;i<8;i++)
   buf[i]=0;
  rc5crypt(buf,output,sk);
  for(i=0;i<8;i++)
   fputc(output[i],fdest);
 }
 fputc(filesize%8,fdest);
 fclose(fsource);
 fclose(fdest);
 return 1;
}
int Decrypt(char *sourcepath,char *destpath,char *key)
{
 unsigned int sk[26]={0};
 Key_Ger(sk,key);
 FILE *fsource;
 FILE *fdest;
 int crypttimes,filesize;
 int i;
 int flag;
 unsigned char buf[8]={0};
 unsigned char output[8]={0};
 fsource=fopen(sourcepath,"rb");
 fdest=fopen(destpath,"wb");
 fseek(fsource,0,2);
 filesize=ftell(fsource);
 rewind(fsource);
 crypttimes=filesize/8;
 fseek(fsource,filesize-1,0);
 flag=fgetc(fsource);
 rewind(fsource);
 while(crypttimes>1){
  for(i=0;i<8;i++)
   buf[i]=fgetc(fsource);
  rc5decrypt(buf,output,sk);
  for(i=0;i<8;i++)
   fputc(output[i],fdest);
  crypttimes--;
 }
 if(flag==0){
  for(i=0;i<8;i++)
   buf[i]=fgetc(fsource);
  rc5decrypt(buf,output,sk);
  for(i=0;i<8;i++)
   fputc(output[i],fdest);
 }
 else{
  for(i=0;i<8;i++)
   buf[i]=fgetc(fsource);
  rc5decrypt(buf,output,sk);
  for(i=0;i<flag;i++)
   fputc(output[i],fdest);
 }
 fclose(fsource);
 fclose(fdest);
 return 1;
}