twenty4/twenty4.c

/*
 ******* THIS IS JUST FOR LEARINING CRYPTO, DO NOT EVER USE THIS FOR ANYTHING *******

 This is the implementation of the fun stream cipher TWENTY4 by Thomas von Dein, 09/2015.
 Published under the public domain, Creative Commons Zero License.

 */

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <ctype.h>
#include <math.h>

typedef uint8_t  byte;
typedef uint32_t word;
typedef uint16_t half;

const byte kbox[] = {
  0x53, 0x61, 0x6c, 0x74, 0x65, 0x64, 0x5f, 0xdf, 0x40, 0xc1, 0x9d, 0x46, 0x33, 0x45, 0x92, 0x95, 
  0xd8, 0x24, 0xf5, 0x1c, 0xe0, 0x29, 0xff, 0xa3, 0x71, 0x6f, 0x35, 0x2e, 0x4b, 0x0d, 0xa7, 0x5d, 
  0x97, 0xe1, 0x98, 0x58, 0x2b, 0xc4, 0xae, 0xe3, 0xec, 0xb8, 0x38, 0xee, 0x91, 0x2c, 0xb4, 0xa0, 
  0xc6, 0x34, 0x1f, 0x57, 0x0e, 0xc3, 0x4f, 0xb9, 0x80, 0x21, 0x5b, 0x06, 0xf6, 0x87, 0xfa, 0x5e, 
  0xe7, 0xda, 0xce, 0xdd, 0x23, 0xe9, 0x03, 0x39, 0xa5, 0x8e, 0xb6, 0xca, 0x3c, 0x7a, 0x44, 0x2d, 
  0x07, 0xcf, 0x1b, 0xd0, 0x94, 0x85, 0xc5, 0x20, 0xaa, 0x81, 0xc9, 0xb7, 0x2f, 0xfb, 0xb2, 0x50, 
  0x54, 0xf0, 0x14, 0xd9, 0x00, 0x67, 0x15, 0x9f, 0xa2, 0x02, 0x93, 0xcc, 0xdb, 0x8d, 0x30, 0x78, 
  0xb1, 0x7b, 0x19, 0xc0, 0x43, 0x6b, 0xbb, 0x2a, 0x3b, 0x4d, 0xe4, 0x08, 0x12, 0x90, 0x32, 0xef, 
  0xe8, 0x5a, 0xac, 0xf4, 0x8c, 0xe2, 0x4e, 0x6d, 0xaf, 0x66, 0xf8, 0xbc, 0x36, 0x72, 0x01, 0x1e, 
  0x68, 0x37, 0x59, 0x51, 0xa6, 0x7c, 0xbe, 0x86, 0x8a, 0x8b, 0xfe, 0x0a, 0x05, 0x52, 0x76, 0x27, 
  0x69, 0x18, 0x22, 0x63, 0x42, 0x4a, 0xad, 0x10, 0xe5, 0xa1, 0xc8, 0xeb, 0xb0, 0x09, 0x6a, 0x4c, 
  0x16, 0xf7, 0xde, 0xfc, 0x7f, 0x7d, 0xdc, 0x99, 0xbd, 0x7e, 0x26, 0xcd, 0xba, 0xc2, 0xa8, 0x04, 
  0x0f, 0x3e, 0x82, 0x1d, 0x89, 0xb5, 0x31, 0xb3, 0x47, 0x6e, 0xf3, 0x0b, 0xd3, 0x84, 0x49, 0x0c, 
  0x3d, 0xd5, 0x9a, 0xd6, 0x9e, 0xd7, 0x8f, 0xa9, 0x79, 0xd4, 0x48, 0x9b, 0x55, 0x56, 0xcb, 0x3a, 
  0xf9, 0xfd, 0xd2, 0xe6, 0x75, 0x1a, 0x11, 0xf2, 0xa4, 0x5c, 0x96, 0x13, 0xea, 0xd1, 0xbf, 0x60, 
  0x28, 0xab, 0x9c, 0x77, 0x83, 0x62, 0x17, 0x41, 0x70, 0x25, 0xf1, 0x3f, 0x88, 0x73, 0xc7, 0xed, 
};


const byte sbox[] = {
  0x61, 0x2d, 0x19, 0xf3, 0xe5, 0xd9, 0xde, 0x5f, 0x41, 0x31, 0xa7, 0xc2, 0x48, 0x02, 0xef, 0x98, 
  0x67, 0xcb, 0x6e, 0x4c, 0xf4, 0x11, 0xfa, 0x87, 0x0f, 0x6f, 0x0a, 0x3b, 0x71, 0x09, 0x1a, 0xb8, 
  0x3c, 0x44, 0xd8, 0xd4, 0xc8, 0x91, 0x6d, 0x8c, 0x2f, 0xce, 0x85, 0x22, 0xd5, 0x08, 0xa6, 0x97, 
  0x68, 0xbc, 0x3a, 0xa0, 0xbf, 0xa5, 0x47, 0x94, 0x83, 0xd1, 0x18, 0x29, 0x03, 0xb2, 0xa4, 0xfe, 
  0xe4, 0x4d, 0xdf, 0x21, 0xc0, 0x70, 0x4f, 0x90, 0x04, 0x40, 0x0b, 0x49, 0xe0, 0x25, 0xd7, 0xda, 
  0xf8, 0x1f, 0x9e, 0x76, 0xbb, 0xaa, 0xc5, 0x2e, 0x72, 0x64, 0xd6, 0x74, 0x10, 0x78, 0xfd, 0x45, 
  0x80, 0x4e, 0x7f, 0x12, 0xb7, 0xc6, 0xea, 0xb3, 0x37, 0x5a, 0xf2, 0xc3, 0xb6, 0x5b, 0x81, 0x95, 
  0xbd, 0xb0, 0xae, 0x8f, 0xd2, 0xcf, 0x1e, 0xc7, 0xee, 0xa1, 0x7a, 0xb9, 0x06, 0xa8, 0xb1, 0x93, 
  0x30, 0xad, 0x33, 0x77, 0x3d, 0x7c, 0xb4, 0x36, 0x92, 0x15, 0x89, 0x7e, 0xe9, 0x17, 0x07, 0x8a, 
  0x9f, 0x32, 0x2c, 0xf9, 0xb5, 0x7d, 0xeb, 0x23, 0xdc, 0x2b, 0x63, 0x88, 0x56, 0x42, 0x84, 0x4b, 
  0x0e, 0xec, 0x8d, 0x7b, 0x05, 0xed, 0xca, 0xe8, 0xe6, 0xba, 0x01, 0x5d, 0x26, 0x28, 0x13, 0x9d, 
  0x54, 0x59, 0xfb, 0xf0, 0xd3, 0xf7, 0xdb, 0xe7, 0xbe, 0x58, 0x5e, 0x99, 0x65, 0x8b, 0x20, 0xa3, 
  0xc1, 0x1c, 0xaf, 0xac, 0x55, 0xe3, 0xdd, 0x62, 0x2a, 0xcc, 0xd0, 0xe2, 0x0c, 0x66, 0x96, 0x8e, 
  0xab, 0xfc, 0xc4, 0x1d, 0x6a, 0x6c, 0x3f, 0x9b, 0x9a, 0x51, 0xa2, 0x86, 0x52, 0x4a, 0x43, 0x14, 
  0x75, 0xff, 0xf5, 0xcd, 0x1b, 0x0d, 0x35, 0x24, 0x9c, 0xe1, 0x60, 0x73, 0x3e, 0x39, 0x53, 0x16, 
  0x50, 0x6b, 0xc9, 0x46, 0x57, 0x5c, 0x69, 0x79, 0x82, 0xf1, 0x27, 0x38, 0x34, 0xf6, 0x00, 0xa9, 

};

byte revsbox[256];

#define K_HASH_ROUNDS 32
#define S_BOX_ROUNDS  17


byte rot8left(byte in, int rot) {
  return (in >> (8-rot)) | (in << rot);
}

byte rot8right(byte in, int rot) {
  return (in << (8-rot)) | (in >> rot);
}

void printbits(byte v) {
  int i;
  for(i = 7; i >= 0; i--) fprintf(stderr, "%c", '0' + ((v >> i) & 1));
}

void dump8(char *n, byte d) {
  fprintf(stderr, "%s: %02x  ", n, d);
  printbits(d);
  fprintf(stderr, "\n");
}

void dumpN(char *n, byte *d, size_t s) {
  int l = strlen(n) + 9;
  fprintf(stderr, "%s (%04ld): ", n, s);
  size_t i;
  int c;
  for (i=0; i<s; ++i) {
    fprintf(stderr, "%02x ", d[i]);
    if(i % 8 == 7 && i > 0) {
      fprintf(stderr, "\n");
      for(c=0; c<l; ++c)
	fprintf(stderr, " ");
    }
  }
  fprintf(stderr, "\n");
}

/* for decryption */
void reverse_sbox() {
  int i;
  for(i=0; i<256; i++)
    revsbox[sbox[i]] = i;
}

byte getiv() {
  FILE *RAND;
  byte rand;
  
  if((RAND = fopen("/dev/urandom", "rb")) == NULL) {
    perror("Could not open /dev/urandom");
    exit(1);
  }
  
  if(fread(&rand, 1, 1, RAND) != 1) {
    perror("Could not read from /dev/urandom");
    exit(1);
  }
    
  fclose(RAND);

  return rand;
}

byte rcon(byte in) {
  byte c=1;
  if(in == 0)  
    return 0; 

  while(in != 1) {
    byte b;
    b = c & 0x80;
    c <<= 1;
    if(b == 0x80) {
      c ^= 0x1b;
    }
    in--;
  }
  return c;
}

/* we use rounds * 8bit sub keys expanded from
   given password */
void keyhash(char *pw, byte *hash) {
  byte iv;
  int i, round;
  unsigned int HEX;
  size_t pwlen;

  if(strncmp(pw, "0x", 2) == 0) {
    /* hex pw */
    sscanf(pw, "0x%02x", &HEX);
    pw[0] = (byte)HEX;
    pwlen = 1;
  }
  else {
    pwlen = strlen(pw);
  }
  
  iv = kbox[(byte)pw[0]];

  /* stretch pw */
  for(i=0; i<K_HASH_ROUNDS; i++) {
    if((size_t)i < pwlen)
      hash[i] = iv ^ pw[i];
    else
      hash[i] = iv ^ kbox[i*8];

    hash[i] = kbox[hash[i]];
    iv = hash[i];
  }
  
  /* diffuse and confuse hash */
  for(round=0; round<K_HASH_ROUNDS; round++) {
    for(i=0; i<K_HASH_ROUNDS; i++) {
      hash[i] = iv ^ (rot8left(hash[i], 3) ^ kbox[rcon(iv)]);
      iv = hash[i];
    }
  }

}

void reverse(byte a[], int sz) {
  int i, j;
  for (i = 0, j = sz; i < j; i++, j--) {
    byte tmp = a[i];
    a[i] = a[j];
    a[j] = tmp;
  }
}

void rotate(byte array[], int size, int amt) {
  if (amt < 0)
    amt = size + amt;
  reverse(array, size-amt-1);
  reverse(array+size-amt, amt-1);
  reverse(array, size-1);
}

void rotatekey(byte *key, byte feedback) {
  rotate(key, S_BOX_ROUNDS, 1);
  int i;
  for(i=0; i<S_BOX_ROUNDS; i++) {
    key[i] = kbox[key[i] ^ feedback];
  }
}

/* actual stream cipher:
   - xor with round key
   - apply sbox
   - rotate left by (round mod 8) bits
   - xor with (round key rotated left by 4 bits [halfes reversed])
*/
byte bytebox(byte in, byte *key, int encrypt) {
  int i;
  byte out = in;

  if(encrypt) {
    for(i=0; i<S_BOX_ROUNDS; i++) {
      out ^= key[i];
      out  = sbox[out];
      out  = rot8left(out, i%8);
      out ^= rot8right(key[i], 4);
    }
    rotatekey(key, out);
  }
  else {
    for(i=S_BOX_ROUNDS-1; i>= 0; i--) {
      out ^= rot8left(key[i], 4);
      out  = rot8right(out, i%8);
      out  = revsbox[out];
      out ^= key[i];
    }
    rotatekey(key, in);
  }
  
  
  return out;
}

/* work on stdin and stdout */
int handleio(byte *key, int encrypt) {
  byte in, out;

  while (fread(&in, 1, 1, stdin) == 1) {
    out = bytebox(in, key, encrypt);
    fwrite(&out, 1, 1, stdout);
  }

  return 0;
}

/* work on stdin and stdout, in CBC 8bit mode */
int cbc_handleio(byte *key, int encrypt) {
  byte in, out, iv;

  if(encrypt) {
    iv = getiv();
    fwrite(&iv, 1, 1, stdout);
  }
  else {
    fread(&iv, 1, 1, stdin);
  }
  
  while (fread(&in, 1, 1, stdin) == 1) {
    if(encrypt) {
      out = bytebox(iv ^ in, key, encrypt);
      iv = out;
    }
    else {
      out = iv ^ bytebox(in, key, encrypt);
      iv = in;
    }

    fwrite(&out, 1, 1, stdout);
  }

  return 0;
}


int main(int argc, char **argv)  {
  byte key[K_HASH_ROUNDS];
  int encrypt;
  
  if(argc != 3) {
    fprintf(stderr, "Usage: stream <passwd> <e|n>\ne=encrypt, n=decrypt\n");
    return 1;
  }
  else {
    encrypt = 0;

    if(strcmp(argv[2], "e") == 0)
      encrypt = 1;

    reverse_sbox();

    keyhash(argv[1], key);

    return handleio(key, encrypt);
  }
}