probando triple DES

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Probando Triple DES implementación en lenguaje C en GNU/Linux.

Probando Triple DES como método de encriptado

El otro día uno de nuestros colaboradores (K) estuvo revisando el algoritmo de encriptación Triple DES*. Después de hacer una búsqueda rápida en emacs-w3m encontró esta pagina web:

https://www.techiedelight.com/3-des-implementation-c/

Eso le permitió muy rápidamente cambiar el código un poco, para evitar usar archivos:

// cc -o out.bin base64.c 3des.c -lm -g3 -Wall -O0 //{weird worked with clang but no with gcc}
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <math.h>
#include <time.h>
#include "base64.h"

#define THREEDES_BUFFER_SIZE 4096

int IP[] = {
  58, 50, 42, 34, 26, 18, 10, 2,
  60, 52, 44, 36, 28, 20, 12, 4,
  62, 54, 46, 38, 30, 22, 14, 6,
  64, 56, 48, 40, 32, 24, 16, 8,
  57, 49, 41, 33, 25, 17,  9, 1,
  59, 51, 43, 35, 27, 19, 11, 3,
  61, 53, 45, 37, 29, 21, 13, 5,
  63, 55, 47, 39, 31, 23, 15, 7
};

int E[] = {
  32,  1,  2,  3,  4,  5,
  4,  5,  6,  7,  8,  9,
  8,  9, 10, 11, 12, 13,
  12, 13, 14, 15, 16, 17,
  16, 17, 18, 19, 20, 21,
  20, 21, 22, 23, 24, 25,
  24, 25, 26, 27, 28, 29,
  28, 29, 30, 31, 32,  1
};

int P[] = {
  16,  7, 20, 21,
  29, 12, 28, 17,
  1, 15, 23, 26,
  5, 18, 31, 10,
  2,  8, 24, 14,
  32, 27,  3,  9,
  19, 13, 30,  6,
  22, 11,  4, 25
};

int FP[] = {
  40, 8, 48, 16, 56, 24, 64, 32,
  39, 7, 47, 15, 55, 23, 63, 31,
  38, 6, 46, 14, 54, 22, 62, 30,
  37, 5, 45, 13, 53, 21, 61, 29,
  36, 4, 44, 12, 52, 20, 60, 28,
  35, 3, 43, 11, 51, 19, 59, 27,
  34, 2, 42, 10, 50, 18, 58, 26,
  33, 1, 41,  9, 49, 17, 57, 25
};

int S1[4][16] = {
  14,  4, 13,  1,  2, 15, 11,  8,  3, 10,  6, 12,  5,  9,  0,  7,
  0, 15,  7,  4, 14,  2, 13,  1, 10,  6, 12, 11,  9,  5,  3,  8,
  4,  1, 14,  8, 13,  6,  2, 11, 15, 12,  9,  7,  3, 10,  5,  0,
  15, 12,  8,  2,  4,  9,  1,  7,  5, 11,  3, 14, 10,  0,  6, 13
};

int S2[4][16] = {
  15,  1,  8, 14,  6, 11,  3,  4,  9,  7,  2, 13, 12,  0,  5, 10,
  3, 13,  4,  7, 15,  2,  8, 14, 12,  0,  1, 10,  6,  9, 11,  5,
  0, 14,  7, 11, 10,  4, 13,  1,  5,  8, 12,  6,  9,  3,  2, 15,
  13,  8, 10,  1,  3, 15,  4,  2, 11,  6,  7, 12,  0,  5, 14,  9
};

int S3[4][16] = {
  10,  0,  9, 14,  6,  3, 15,  5,  1, 13, 12,  7, 11,  4,  2,  8,
  13,  7,  0,  9,  3,  4,  6, 10,  2,  8,  5, 14, 12, 11, 15,  1,
  13,  6,  4,  9,  8, 15,  3,  0, 11,  1,  2, 12,  5, 10, 14,  7,
  1, 10, 13,  0,  6,  9,  8,  7,  4, 15, 14,  3, 11,  5,  2, 12
};

int S4[4][16] = {
  7, 13, 14,  3,  0,  6,  9, 10,  1,  2,  8,  5, 11, 12,  4, 15,
  13,  8, 11,  5,  6, 15,  0,  3,  4,  7,  2, 12,  1, 10, 14,  9,
  10,  6,  9,  0, 12, 11,  7, 13, 15,  1,  3, 14,  5,  2,  8,  4,
  3, 15,  0,  6, 10,  1, 13,  8,  9,  4,  5, 11, 12,  7,  2, 14
};

int S5[4][16] = {
  2, 12,  4,  1,  7, 10, 11,  6,  8,  5,  3, 15, 13,  0, 14,  9,
  14, 11,  2, 12,  4,  7, 13,  1,  5,  0, 15, 10,  3,  9,  8,  6,
  4,  2,  1, 11, 10, 13,  7,  8, 15,  9, 12,  5,  6,  3,  0, 14,
  11,  8, 12,  7,  1, 14,  2, 13,  6, 15,  0,  9, 10,  4,  5,  3
};

int S6[4][16] = {
  12,  1, 10, 15,  9,  2,  6,  8,  0, 13,  3,  4, 14,  7,  5, 11,
  10, 15,  4,  2,  7, 12,  9,  5,  6,  1, 13, 14,  0, 11,  3,  8,
  9, 14, 15,  5,  2,  8, 12,  3,  7,  0,  4, 10,  1, 13, 11,  6,
  4,  3,  2, 12,  9,  5, 15, 10, 11, 14,  1,  7,  6,  0,  8, 13
};

int S7[4][16]= {
  4, 11,  2, 14, 15,  0,  8, 13,  3, 12,  9,  7,  5, 10,  6,  1,
  13,  0, 11,  7,  4,  9,  1, 10, 14,  3,  5, 12,  2, 15,  8,  6,
  1,  4, 11, 13, 12,  3,  7, 14, 10, 15,  6,  8,  0,  5,  9,  2,
  6, 11, 13,  8,  1,  4, 10,  7,  9,  5,  0, 15, 14,  2,  3, 12
};

int S8[4][16]= {
  13,  2,  8,  4,  6, 15, 11,  1, 10,  9,  3, 14,  5,  0, 12,  7,
  1, 15, 13,  8, 10,  3,  7,  4, 12,  5,  6, 11,  0, 14,  9,  2,
  7, 11,  4,  1,  9, 12, 14,  2,  0,  6, 10, 13, 15,  3,  5,  8,
  2,  1, 14,  7,  4, 10,  8, 13, 15, 12,  9,  0,  3,  5,  6, 11
};

int PC1[] = {
  57, 49, 41, 33, 25, 17,  9,
  1, 58, 50, 42, 34, 26, 18,
  10,  2, 59, 51, 43, 35, 27,
  19, 11,  3, 60, 52, 44, 36,
  63, 55, 47, 39, 31, 23, 15,
  7, 62, 54, 46, 38, 30, 22,
  14,  6, 61, 53, 45, 37, 29,
  21, 13,  5, 28, 20, 12,  4
};

int PC2[] = {
  14, 17, 11, 24,  1,  5,
  3, 28, 15,  6, 21, 10,
  23, 19, 12,  4, 26,  8,
  16,  7, 27, 20, 13,  2,
  41, 52, 31, 37, 47, 55,
  30, 40, 51, 45, 33, 48,
  44, 49, 39, 56, 34, 53,
  46, 42, 50, 36, 29, 32
};

int SHIFTS[] = { 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1 };

int LEFT[17][32], RIGHT[17][32];
int IPtext[64];
int EXPtext[48];
int XORtext[48];
int X[8][6];
int X2[32];
int R[32];
int g_key56bit[56];
int g_key48bit[17][48];
int CIPHER[64];
int ENCRYPTED[64];

void expansion_function(int pos, int text) {
  for (int i = 0; i < 48; i++)
    if(E[i] == pos + 1)
      EXPtext[i] = text;
}

int initial_permutation(int pos, int text) {
  int i;
  for (i = 0; i < 64; i++)
    if(IP[i] == pos + 1)
      break;
  IPtext[i] = text;

  return 0;
}

int threedes_f1(int i) {
  int r, c, b[6];

  for (int j = 0; j < 6; j++)
    b[j] = X[i][j];

  r = b[0] * 2 + b[5];
  c = 8 * b[1] + 4 * b[2] + 2 * b[3] + b[4];
  if(i == 0) return S1[r][c];
  else if(i == 1) return S2[r][c];
  else if(i == 2)    return S3[r][c];
  else if(i == 3)    return S4[r][c];
  else if(i == 4)    return S5[r][c];
  else if(i == 5)    return S6[r][c];
  else if(i == 6)    return S7[r][c];
  else if(i == 7)    return S8[r][c];
  return 0;

}

int threedes_XOR(int a, int b) {
  return (a ^ b);
}

int threedes_to_bits(int value) {
  int k, j, m;
  static int i;

  if(i % 32 == 0)
    i = 0;
  for (j = 3; j >= 0; j--) {
    m = 1 << j;
    k = value & m;
    if(k == 0)
      X2[3 - j + i] = '0' - 48;
    else
      X2[3 - j + i] = '1' - 48;
  }
  i = i + 4;
  return 0;
}

int threedes_s_box(int XORtext[]) {
  int k = 0;
  int value;

  for (int i = 0; i < 8; i++)
    for (int j = 0; j < 6; j++)
      X[i][j] = XORtext[k++];

  for (int i = 0; i < 8; i++) {
    value = threedes_f1(i);
    threedes_to_bits(value);
  }
  return 0;
}

int threedes_p_box(int pos, int text) {
  int i;

  for (i = 0; i < 32; i++)
    if(P[i] == pos + 1)
      break;
  R[i] = text;
  return 0;
}

void threedes_cipher(int Round, int mode) {
  for (int i = 0; i < 32; i++)
    expansion_function(i, RIGHT[Round - 1][i]);

  for (int i = 0; i < 48; i++) {
    if(mode == 0)
      XORtext[i] = threedes_XOR(EXPtext[i], g_key48bit[Round][i]);
    else
      XORtext[i] = threedes_XOR(EXPtext[i], g_key48bit[17 - Round][i]);

  }

  threedes_s_box(XORtext);

  for (int i = 0; i < 32; i++)
    threedes_p_box(i, X2[i]);

  for (int i = 0; i < 32; i++)
    RIGHT[Round][i] = threedes_XOR(LEFT[Round - 1][i], R[i]);
}

void final_permutation(int pos, int text) {
  int i;

  for (i = 0; i < 64; i++)
    if(FP[i] == pos + 1)
      break;

  ENCRYPTED[i] = text;
}

void convert_to_binary(int n, char _uno[]) {
  int k, m;

  for (int i = 7; i >= 0; i--) {
    m = 1 << i;
    k = n & m;
    _uno[ strlen((const char*)_uno) ] = ((k == 0)?48:49);
  }
}

int convert_char_to_bit(long int _n, const char *_plain_text, char _uno[]) {
  char ch;
  int i = 0;
  int n = _n * 8;

  while (i< n) {
    ch = _plain_text[i];
    if((int)ch == -1)
      break;
    i++;
    convert_to_binary(ch, _uno);
  }

  return 0;
}

void convert_array_to_bits(int ch[], int _out_len, char *_array_out_block) {
  int value = 0;
  char *myblock;

  myblock = _array_out_block;
  for (int i = 7; i >= 0; i--) {
    value += (int)pow(2, i) * ch[7 - i];
  }

  myblock[ _out_len ] = (char)value;
}

int bit_to_char(char *_array_out_block) {
  int j;

  j = 0;
  for (int i = 0; i < 64; i = i + 8) {
    convert_array_to_bits(&ENCRYPTED[i], j, _array_out_block);
    j++;
  }

  return 0;
}

void threedes_key56to48(int round, int pos, int text) {
  int i;

  for (i = 0; i < 56; i++)
    if(PC2[i] == pos + 1)
      break;

  g_key48bit[round][i] = text;
}

int threedes_key64to56(int pos, int text) {
  int i;

  for (i = 0; i < 56; i++)
    if(PC1[i] == pos + 1)
      break;

  g_key56bit[i] = text;
  return 0;
}

void threedes_key64to48(unsigned int key[]) {
  int k, backup[17][2];
  int CD[17][56];
  int C[17][28], D[17][28];

  for (int i = 0; i < 64; i++)
    threedes_key64to56(i, key[i]);

  for (int i = 0; i < 56; i++)
    if(i < 28)
      C[0][i] = g_key56bit[i];
    else
      D[0][i - 28] = g_key56bit[i];

  for (int x = 1; x < 17; x++) {
    int shift = SHIFTS[x - 1];

    for (int i = 0; i < shift; i++)
      backup[x - 1][i] = C[x - 1][i];
    for (int i = 0; i < (28 - shift); i++)
      C[x][i] = C[x - 1][i + shift];
    k = 0;
    for (int i = 28 - shift; i < 28; i++)
      C[x][i] = backup[x - 1][k++];

    for (int i = 0; i < shift; i++)
      backup[x - 1][i] = D[x - 1][i];
    for (int i = 0; i < (28 - shift); i++)
      D[x][i] = D[x - 1][i + shift];
    k = 0;
    for (int i = 28 - shift; i < 28; i++)
      D[x][i] = backup[x - 1][k++];
  }

  for (int j = 0; j < 17; j++) {
    for (int i = 0; i < 28; i++)
      CD[j][i] = C[j][i];
    for (int i = 28; i < 56; i++)
      CD[j][i] = D[j][i - 28];
  }

  for (int j = 1; j < 17; j++)
    for (int i = 0; i < 56; i++)
      threedes_key56to48(j, i, CD[j][i]);
}

void threedes_encryption(long int plain[], char _out[]) {
  for (int i = 0; i < 64; i++)
    initial_permutation(i, plain[i]);

  for (int i = 0; i < 32; i++)
    LEFT[0][i] = IPtext[i];
  for (int i = 32; i < 64; i++)
    RIGHT[0][i - 32] = IPtext[i];

  for (int k = 1; k < 17; k++) {
    threedes_cipher(k, 0);

    for (int i = 0; i < 32; i++)
      LEFT[k][i] = RIGHT[k - 1][i];
  }

  for (int i = 0; i < 64; i++) {
    if(i < 32)
      CIPHER[i] = RIGHT[16][i];
    else
      CIPHER[i] = LEFT[16][i - 32];
    final_permutation(i, CIPHER[i]);
  }

  for (int i = 0; i < 64; i++) {
    _out[i] = ENCRYPTED[i] ==1 ?'1':'0';
  }

}

void threedes_decryption(long int plain[], char *_out) {
  for (int i = 0; i < 64; i++)
    initial_permutation(i, plain[i]);

  for (int i = 0; i < 32; i++)
    LEFT[0][i] = IPtext[i];

  for (int i = 32; i < 64; i++)
    RIGHT[0][i - 32] = IPtext[i];

  for (int k = 1; k < 17; k++) {
    threedes_cipher(k, 1);

    for (int i = 0; i < 32; i++)
      LEFT[k][i] = RIGHT[k - 1][i];
  }

  for (int i = 0; i < 64; i++) {
    if(i < 32)
      CIPHER[i] = RIGHT[16][i];
    else
      CIPHER[i] = LEFT[16][i - 32];
    final_permutation(i, CIPHER[i]);
  }

  for (int i = 0; i < 64; i++) {
    _out[i] = (ENCRYPTED[i] == 1)?'1':'0';
  }

}

void decrypt_with_key(long int n, const char *_str_to_decrypt, char _out[], char *_array_out_block ) {
  // destroy contents of these files (from previous runs) {_out, _array_out_block}
  long int plain[n * 64];
  int i = -1;
  int count;
  char ch;

  count = strlen(_str_to_decrypt);
  while (i < count) {
    ch = _str_to_decrypt[i+1];
    plain[++i] = ch - 48;
  }

  for (int i = 0; i < n; i++) {
    threedes_decryption(plain + i * 64, _out); // dos.txt
    bit_to_char(_array_out_block); // result.txt
  }
}

void encrypt_with_key(long int n, const char *_str_to_encrypt, char _out[]) {
  memset(_out, 0, THREEDES_BUFFER_SIZE);

  long int plain[n * 64];
  int i = -1;
  int count;
  char ch;

  count = strlen(_str_to_encrypt);
  while (i < count) {
    ch = _str_to_encrypt[i+1];
    plain[++i] = ch - 48;
  }

  for (int i = 0; i < n; i++) {
    threedes_encryption(plain + 64 * i, _out); // 2.txt
  }
}

// key could be on a database or file as it was originally; K1= first 64 chars on the array
void fill_and_adapt_key(unsigned int _key[]) {
  int i = 0, ch;
  unsigned int key_char[192] = {
        '0', '1', '1', '0', '0', '0', '1', '0', '0', '1', '1', '0', '0', '0', '0', '1', '0', '1', '1', '0', '1', '1', '0', '0', '0', '1', '1', '1', '0', '1', '0', '0', '0', '1', '1', '0', '0', '0', '0', '1', '0', '1', '1', '1', '1', '0', '1', '0', '0', '1', '1', '0', '0', '0', '0', '1', '0', '1', '1', '1', '0', '0', '1', '0',
        '0', '1', '1', '0', '0', '1', '1', '0', '0', '1', '1', '1', '0', '0', '1', '0', '0', '1', '1', '0', '0', '0', '0', '1', '0', '1', '1', '0', '1', '1', '1', '0', '0', '1', '1', '0', '0', '0', '1', '1', '0', '1', '1', '0', '1', '0', '0', '1', '0', '1', '1', '1', '0', '0', '1', '1', '0', '1', '1', '0', '0', '0', '1', '1',
        '0', '1', '1', '0', '1', '0', '1', '0', '0', '1', '1', '0', '0', '1', '0', '1', '0', '1', '1', '1', '0', '0', '1', '0', '0', '1', '1', '0', '0', '1', '0', '1', '0', '1', '1', '0', '1', '1', '0', '1', '0', '1', '1', '0', '1', '0', '0', '1', '0', '1', '1', '0', '0', '0', '0', '1', '0', '1', '1', '1', '0', '0', '1', '1'
      };

  while (i < 192) {
    ch = key_char[i];
    _key[i++] = ch - 48;
  }

}

const char *encrypt_entry(const char *_input_for_encryption, char _encrypt_block[]) {
  unsigned char myunotxt[THREEDES_BUFFER_SIZE];
  unsigned char mydostxt[THREEDES_BUFFER_SIZE];
  unsigned char myresulttxt[THREEDES_BUFFER_SIZE];
  unsigned int key[192];
  size_t ret_code;
  long int n;

  fill_and_adapt_key(key);

  memset(myunotxt, 0, THREEDES_BUFFER_SIZE);
  memset(mydostxt, 0, THREEDES_BUFFER_SIZE);
  memset(myresulttxt, 0, THREEDES_BUFFER_SIZE);
  n = strlen(_input_for_encryption) / 8; // @minimun 8
  convert_char_to_bit(n, _input_for_encryption, (char*)myunotxt); //  convert _input_for_encryption to bit

  // Encryption starts
  // DES encrypt with K1, DES decrypt with K2, then DES encrypt with K3.
  threedes_key64to48(key);
  encrypt_with_key(n, (const char*)myunotxt, (char*)mydostxt);    // convert  using K1

  threedes_key64to48(key + 64);
  decrypt_with_key(n, (const char*)mydostxt, (char*)myunotxt, (char*)myresulttxt);    // convert  using K2

  threedes_key64to48(key + 128);
  encrypt_with_key(n, (const char*)myunotxt, (char*)mydostxt);    // convert  using K3

  memset(myresulttxt, 0, THREEDES_BUFFER_SIZE); // clean before calling bit_to_char
  bit_to_char((char*)myresulttxt);
  ret_code = base64_encode((char*)_encrypt_block, THREEDES_BUFFER_SIZE, (const char*)myresulttxt, strlen((const char*)myresulttxt));
  memset(myunotxt, 0, THREEDES_BUFFER_SIZE);
  memset(mydostxt, 0, THREEDES_BUFFER_SIZE);
  memset(myresulttxt, 0, THREEDES_BUFFER_SIZE);

  return (ret_code != -1)?_encrypt_block:NULL;
}

const char *decrypt_entry(const char *_input_for_decryption, int _n_value, char _decrypt_block[]) {
  unsigned char myunotxt[THREEDES_BUFFER_SIZE];
  unsigned char mydostxt[THREEDES_BUFFER_SIZE];
  unsigned char myresulttxt[THREEDES_BUFFER_SIZE];
  unsigned int key[192];
  size_t ret_code;

  fill_and_adapt_key(key);

  memset(myunotxt, 0, THREEDES_BUFFER_SIZE);
  memset(mydostxt, 0, THREEDES_BUFFER_SIZE);
  memset(myresulttxt, 0, THREEDES_BUFFER_SIZE);
  ret_code = base64_decode(_decrypt_block, base64_decoded_length(strlen(_input_for_decryption)), _input_for_decryption, strlen(_input_for_decryption));
  if (ret_code == -1) {
    fprintf(stderr, "my_new_decrpyt Err when decoding base64\n");
  }
  convert_char_to_bit(_n_value, _decrypt_block, (char*)myunotxt);
  strcpy((char*)mydostxt, (const char*)myunotxt); // uno to dos
  memset(myunotxt, 0, THREEDES_BUFFER_SIZE);
  memset(_decrypt_block, 0, THREEDES_BUFFER_SIZE);

  // threedes_decryption starts (reverse of threedes_encryption)
  // decrypt with K3, encrypt with K2, then decrypt with K1.
  threedes_key64to48(key + 128);
  decrypt_with_key(_n_value, (const char*)mydostxt, (char*)myunotxt, (char*)myresulttxt);    // convert using K3

  threedes_key64to48(key + 64);
  encrypt_with_key(_n_value, (const char*)myunotxt, (char*)mydostxt);    // convert  using K2

  threedes_key64to48(key);
  decrypt_with_key(_n_value, (const char*)mydostxt, (char*)myunotxt, (char*)myresulttxt);    // convert using K3 {also put the content on result}

  strcpy(_decrypt_block, (const char*)myresulttxt); // result to block
  memset(myunotxt, 0, THREEDES_BUFFER_SIZE);
  memset(mydostxt, 0, THREEDES_BUFFER_SIZE);
  memset(myresulttxt, 0, THREEDES_BUFFER_SIZE);

  return (ret_code != -1)?_decrypt_block:NULL;
}

int main() {
  const char *input_for_encryption = "kipuamut";
  const char *encryption_output;
  const char *input_for_decryption = "W5i6FPHcSwk=";
  const char *decryption_output;
  char encrypt_block[THREEDES_BUFFER_SIZE];
  char decrypt_block[THREEDES_BUFFER_SIZE];

  memset(encrypt_block, 0, THREEDES_BUFFER_SIZE);
  memset(decrypt_block, 0, THREEDES_BUFFER_SIZE);

  encryption_output = encrypt_entry(input_for_encryption, encrypt_block);
  if (encryption_output) {
    fprintf(stdout, "mymain base64-encoded=%s\n", encryption_output);
  }
  // n_value (second parameter) could need to be stored on database perhaps {YMMV}
  decryption_output = decrypt_entry(input_for_decryption, (strlen(input_for_encryption) / 8), decrypt_block);
  if (decryption_output) {
    fprintf(stdout, "mymain desencriptado=%s\n", decryption_output);
  }

  memset(encrypt_block, 0, THREEDES_BUFFER_SIZE);
  memset(decrypt_block, 0, THREEDES_BUFFER_SIZE);
  return 0;
}

Al terminar de codificar, nuestro colaborador se dio cuenta que el código le arrojaba un 'segmentation fault'. Tardo un poco en recompilarlo con clang y en el clang el código se ejecuta como deberia.

La fecha de este articulo es 2021-01-25.

En este caso la versión del gcc es:

,—- [ ]

`—-

la versión del clang es:

,—- [ ]

`—-

Si alguien tiene una idea de como resolver este problema 'segmentation fault' que presenta el gcc, nos lo hace saber por correo electrónico dirigido a:

—8<—————cut here—————start————->8—
c
o
n
t
a
c
t
o
@kipuamutay.com
—8<—————cut here—————end—————>8—

Los otros 2 archivos base64.c y base64.h pueden ser descargados del ccan:

https://ccodearchive.net/list.html

Disfruten codificando.

Design by Andreas Viklund ·