Code:

 

/* Baldr   : a stream cipher
  Author : Loki
  Version: 0.1
*/

/* Usage: baldr key input_file output_file */

#include <stdio.h>

#define decrypt 100
#define encrypt 101

void print_usage(void);

int main(int argc, char *argv[]) {
FILE *plain_text, *cipher_text;
char *user_key;
int current_byte, mode;

/* check for user key */
if ((user_key = argv[1]) && *user_key!='\0') {

 /* check for file in*/
 if ((plain_text = fopen(argv[2], "rb")) != NULL) {

   /* check for file out*/
  if ((cipher_text = fopen(argv[3], "wb")) != NULL) {

   /* main encryption/decryption routine */

  mode = *argv[4];
   switch(mode) {
    case encrypt:
     /* while we are still reading data */
     while ((current_byte = fgetc(plain_text)) != EOF) {

     /* has user key expired ? if so reset it*/
     if (*user_key == '\0')
      user_key = argv[1];
     
     /* read current byte and encrypted it */
     current_byte += *user_key;
     current_byte ^= ~*user_key++;
   
     /* write current byte */
     fputc(current_byte, cipher_text);
     }
    break;
    case decrypt:
    /* while we are still reading data */
    while ((current_byte = fgetc(plain_text)) != EOF) {

     /* has user key expired ? if so reset it*/
     if (*user_key == '\0')
      user_key = argv[1];
     
     /* read current byte and decrypted it */
     current_byte ^= ~*user_key;
     current_byte -= *user_key++;
   
     /* write current byte */
     fputc(current_byte, cipher_text);
    }
    break;
   }
  fflush(cipher_text);
  fclose(cipher_text);
  } else {
   /* error bad input file passed */
   printf("ERROR WRITING OUTPUT_FILE\n");
   print_usage();
   }
 /* flush and close input_file */
 fflush(plain_text);
 fclose(plain_text);
 } else {
  /* error bad input file passed */
  printf("ERROR READING INPUT_FILE\n");
  print_usage();
  }
} else {
/* error no key passed */
printf("ERROR READING KEY\n");
print_usage();
}
return 0;
}

void print_usage(void) {
printf("Usage:\tbaldr key input_file output_file mode\n");
printf("modes are: e for encrypt, d for decrypt\n");
}


Code:

 

/* Baldr   : a stream cipher
  Author : Loki
  Version: 0.2
*/

/* Usage: baldr key input_file output_file */

#include <stdio.h>

#define decrypt 100
#define encrypt 101

void print_usage(void);

static inline int baldr_encrypt(int a, int b);
static inline int baldr_decrypt(int a, int b);

int main(int argc, char *argv[]) {
FILE *plain_text, *cipher_text;
char *user_key;
register int current_byte;
   int mode;

/* check for user key */
if ((user_key = argv[1]) && *user_key!='\0') {

 /* check for file in*/
 if ((plain_text = fopen(argv[2], "rb")) != NULL) {

   /* check for file out*/
  if ((cipher_text = fopen(argv[3], "wb")) != NULL) {

   /* main encryption/decryption routine */

  mode = *argv[4];
   switch(mode) {
    case encrypt:
     /* while we are still reading data */
     while ((current_byte = fgetc(plain_text)) != EOF) {

     /* has user key expired ? if so reset it*/
     if (*user_key == '\0')
      user_key = argv[1];
     current_byte  = baldr_encrypt(current_byte,*user_key);
     
     
        *user_key++;
     /* write current byte */
     fputc(current_byte, cipher_text);
     }
    break;
    case decrypt:
    /* while we are still reading data */
    while ((current_byte = fgetc(plain_text)) != EOF) {

     /* has user key expired ? if so reset it*/
     if (*user_key == '\0')
      user_key = argv[1];

                       current_byte = baldr_decrypt(current_byte,*user_key);
                       
        *user_key++;
     /* write current byte */
     fputc(current_byte, cipher_text);
    }
    break;
   }
  fflush(cipher_text);
  fclose(cipher_text);
  } else {
   /* error bad input file passed */
   printf("ERROR WRITING OUTPUT_FILE\n");
   print_usage();
   }
 /* flush and close input_file */
 fflush(plain_text);
 fclose(plain_text);
 } else {
  /* error bad input file passed */
  printf("ERROR READING INPUT_FILE\n");
  print_usage();
  }
} else {
/* error no key passed */
printf("ERROR READING KEY\n");
print_usage();
}
return 0;
}

void print_usage(void) {
printf("Usage:\tbaldr key input_file output_file mode\n");
printf("modes are: e for encrypt, d for decrypt\n");
}

static inline int baldr_encrypt(int a, int b) {
   register int t;
   
   t   = a ^ b;
   t <<= 1;
   t  ^= b;
   
   return t;
   }
   
static inline int baldr_decrypt(int a, int b) {
   register int t;
   
   t = a ^ b;
   t >>= 1;
   t ^= b;
   
   return t;
   }


rot13

Aug 17 2006, 10:20 AM

Maybe you could take this a little farther and explain why this increases the security of the cipher. I was kinda hoping you might take a stab at explaining how someone might break the cipher, then make changes to it based on that. I don't think it helps much to add in things from other ciphers without understanding why they are necessary.

Code:

 


#include <stdio.h>
#include <memory.h>
#include <stdlib.h>

int main(int argc, char **argv)
{
   int ch, pos;
   int counts[64][256];
   int max1[64];
   int max1count[64];
   FILE *infile;

   if (argc < 2)
   {
       fprintf(stderr, "Please supply the input filename");
       exit(1);
   }

   if ((infile = fopen(argv[1], "rb")) == NULL)
   {
       perror("fopen");
       exit(1);
   }

   pos = 0;

   memset(counts, 0, sizeof(counts));
   memset(max1, 0, sizeof(max1));
   memset(max1count, 0, sizeof(max1count));

   while ((ch = fgetc(infile)) != EOF)
   {
       ch = ch & 0xff;
       counts[pos][ch]++;
       if (counts[pos][ch] > max1count[pos])
       {
           max1[pos] = ch;
           max1count[pos] = counts[pos][ch];
       }
       pos = (pos+1)%64;
   }
   fclose(infile);

   if ((infile = fopen(argv[1], "rb")) == NULL)
   {
       perror("fopen");
       exit(1);
   }

   pos = 0;
   while ((ch = fgetc(infile)) != EOF)
   {
       ch = (ch&0xff) ^ (max1[pos]^0x20);

       putchar(ch);
       pos = (pos+1)%64;
   }
   fclose(infile);
}