* USAGE: pass a key made up of 8 16-bit numbers (word16) in an array
("word16 key[8];"), an input FILE * and an output temporary
FILE * to either encode_file() or decode_file().
where the key comes from is up to you.
then call swap_files_and_clean_up() with the original file's
name as the argument, to replace the original file
with the encoded data (stored in the temporary file).
*/
#include "idea.h"
static uint16 inv(uint16 x)
{
uint16 t0,t1;
uint16 q,y;
if (x<=1)
return x;
t1=(uint16)(0x10001l/x);
y=(uint16)(0x10001l%x);
if (y==1)
return low16(1-t1);
t0=1;
do
{
q=x/y;
x=x%y;
t0+=q*t1;
if (x==1)
return t0;
q=y/x;
y=y%x;
t1+=q*t0;
} while (y!=1);
return low16(1-t1);
}
static void en_key_idea(word16 *userkey, word16 *Z)
{
int i,j;
/* shifts */
for (j=0;j<8;j++)
Z[j]=*userkey++;
for (i=0;j<KEYLEN;j++)
{
i++;
Z[i+7]=((Z[i&7] << 9) | (Z[i+1 & 7] >> 7));
Z+=i&8;
i&=7;
}
}
static void de_key_idea(IDEAkey Z,IDEAkey DK)
{
int j;
uint16 t1,t2,t3;
IDEAkey T;
word16 *p=T+KEYLEN;
t1=inv(*Z++);
t2=-*Z++;
t3=-*Z++;
*--p=inv(*Z++);
*--p=t3;
*--p=t2;
*--p=t1;
for (j=1;j<ROUNDS;j++)
{
t1=*Z++;
*--p=*Z++;
*--p=t1;
t1=inv(*Z++);
t2=-*Z++;
t3=-*Z++;
*--p=inv(*Z++);
*--p=t2;
*--p=t3;
*--p=t1;
}
t1=*Z++;
*--p=*Z++;
*--p=t1;
t1=inv(*Z++);
t2=-*Z++;
t3=-*Z++;
*--p=inv(*Z++);
*--p=t3;
*--p=t2;
*--p=t1;
/*copy and destroy temp copy*/
for(j=0,p=T;j<KEYLEN;j++)
{
*DK++=*p;
*p++=0;
}
}
uint16 mul(uint16 a, uint16 b)
{
word32 p;
if (a)
{
if (b)
{
p=(word32)a*b;
b=(uint16)(low16(p));
a=(uint16)(p>>16);
return b-a+(b<a);
}
else
{
return 1-a;
}
}
else
return 1-b;
}
#define MUL(x,y) (x=mul(low16(x),y))
#define CONST
static void cipher_idea(word16 in[4],word16 out[4],register CONST IDEAkey Z)
{
register uint16 x1,x2,x3,x4,t1,t2;
int r=ROUNDS;
x1=*in++; x2=*in++;
x3=*in++; x4=*in;
do
{
MUL(x1,*Z++);
x2+=*Z++;
x3+=*Z++;
MUL(x4,*Z++);
t2=x1^x3;
MUL(t2,*Z++);
t1=t2+(x2^x4);
MUL(t1,*Z++);
t2=t1+t2;
x1^=t1;
x4^=t2;
t2^=x2;
x2=x3^t1;
x3=t2;
} while (--r);
MUL(x1,*Z++);
*out++=x1;
*out++=(x3+*Z++);
*out++=(x2+*Z++);
MUL(x4,*Z);
*out=x4;
}
char read_char_from_file(FILE *fp)
{
char temp=0;
if ((fread(&temp,sizeof(char),1,fp))!=1)
end_of_file=1;
return (temp);
}
word16 read_word16_from_file(FILE *fp)
{
word16 temp=0;
if ((fread(&temp,sizeof(word16),1,fp))!=1)
end_of_file=1;
return temp;
}
void write_char_to_file(char data,FILE *fp)
{
if ((fwrite(&data,sizeof(char),1,fp))!=1)
{
printf("Fatal Error writing output file!!!\n");
exit(-1);
}
}
void write_word16_to_file(word16 data,FILE *fp)
{
if ((fwrite(&data,sizeof(word16),1,fp))!=1)
{
printf("Fatal Error writing output file!!!\n");
exit(-1);
}
}
void cipher_file(FILE *in,FILE *out,word16 *key)
{
word16 input[4],output[4];
IDEAkey Z;
int x,y;
int count=0;
long length;
int temp;
en_key_idea(key,Z);
end_of_file=0;
length=filelength(fileno(in));
fwrite(&length,sizeof(long),1,out);
while (!end_of_file)
{
x=0;
while (x<4)
{
input[x]=((word16)(read_char_from_file(in)<<8));
if (!end_of_file)
{
temp=read_char_from_file(in);
if (temp<0) temp+=256;
input[x]=input[x]|temp;
x++;
}
if (end_of_file)
{
while (x<4) input[x++]=0;
break;
}
}
cipher_idea(input,output,Z);
for (y=0;y<x;y++)
{
if (noisy) if (count++%256==0) printf(".");
write_word16_to_file(output[y],out);
}
}
}
void decipher_file(FILE *in,FILE *out,word16 *key)
{
word16 input[4],output[4];
int x,y;
IDEAkey Z,DK;
int count=0;
long length=0;
en_key_idea(key,Z);
de_key_idea(Z,DK);
end_of_file=0;
fread(&length,sizeof(long),1,in);
while (!end_of_file)
{
x=0;
while (x<4)
{
input[x]=read_word16_from_file(in);
if (end_of_file)
break;
x++;
}
cipher_idea(input,output,DK);
for (y=0;y<x;y++)
{
if (noisy) if (count++%256==0) printf(".");
if (length-->0)
write_char_to_file(((char)(output[y]>>8)),out);
if (length-->0)
write_char_to_file(((char)(output[y]&255)),out);
}
}
}
void swap_files_and_clean_up(char *file)
{
long fsize,count;
FILE *fp;
char temp[100];
if (overwrite)
{
if ((fp=fopen(file,"r+b"))==NULL)
{
printf("\nError overwriting old file, security compromised.\n");
}
else
{
fseek(fp,0l,SEEK_END);
fsize=ftell(fp);
fseek(fp,0l,SEEK_SET);
for (count=0;count<fsize;count++)
fputc('0',fp);
fclose(fp);
}
if ((remove(file))!=0)
{
printf("\nERROR removing old file <%s>\n",file);
printf("encoded data remains in temporary file <%s>\n",tempfilename);
exit(-1);
}
}
else
{
strcpy(temp,file);
file=strtok(temp,".");
strcat(file,".enc");
}
if ((rename(tempfilename,file))!=0)
{
printf("\nERROR renaming temporary file <%s>!!\n",tempfilename);
printf("Data is safely processed and stored in that file.\n");
exit(-1);
}
}
/*-----------------------------------------------*/
#define KBYTES 1024
void getuserkeyfromargv(word16 *key,char *arg)
{
int x;
for (x=0;x<strlen(arg) && x<8;x++)
{
if (x==0) key[x]=arg[x]<<8;
else key[x]=((arg[x]<<8)|(key[x-1]>>8));
}
if (strlen(arg)>8) printf ("\nONLY first *8* characters of key used!!!\n");
if (x<8) while (x<8) key[x++]=0;
}
main(int argc, char **argv)
{
word16 userkey[8];
char filename[100];
FILE *fp,*temp;
int to_or_from;
noisy=1;
overwrite=0;
if (argc!=4)
{
printf("\nUsage: idea filename.ext [e|d[w]] key\n");
printf(" e=encode d=decode w=overwrite file\n");
printf(" NOTE: Key must be no longer than 8 characters long!!!\n");
exit(-1);
}
else
{
strncpy(filename,argv[1],99);
filename[99]='\0';
if (argv[2][0]=='e') to_or_from=1;
else if (argv[2][0]=='d') to_or_from=0;
else
{
printf("\nUsage: idea filename.ext [e|d[w]] key\n");
printf("e=encrypt d=decrypt w=overwrite file\n");
printf(" NOTE: Key must be no longer than 8 characters long!!!\n");
exit(-1);
}
if (argv[2][1]=='w') overwrite=1;
getuserkeyfromargv(userkey,argv[3]);
}
if ((fp=fopen(filename,"r+b"))==NULL)
{
printf("\nError opening File %s\n",filename);
exit (-1);
}
if ((temp=fopen(tempfilename,"w+b"))==NULL)
{
printf("\nError opening temporary file\n");
exit(-1);
}
if (to_or_from==1)
{
printf("\nEncoding file %s ",filename);
cipher_file(fp,temp,userkey);
}
else
{
printf("\nDecoding file %s ",filename);
decipher_file(fp,temp,userkey);
}
fclose (fp);
fclose(temp);
swap_files_and_clean_up(filename);
return 0;
}
