Blowfish code in Matlab

[klun]

Can anyone help me in creating matlab source code for Blowfish algorithm, for encrypting and decrypting password? need it urgently.

 

[D.A.(Tony)Stewart]

Blowfish and Twofish are open source codes by B. Schneirer, latter being very efficient runnerup for AES2000 with no backdoors.

 

[FvM]

A basic learning objective of this homework problem is how to implement modular arithmetic in Matlab. Get an idea from this TEA related thread https://www.edaboard.com/threads/310428/

 

[klun]

Thanks for the replies. I studied that many of the Blowfish algorithm is written in C or C++, which giving me trouble as the requirement needs it to be written in Matlab. So any examples of Blowfish code for me to refer to?

 

[bigdogguru]

Perhaps if you post what you've written in C or C++ thus far, using CODE or SYNTAX tags, and point out specific issues you are experiencing with your code, we might be able to provide you with additional advice.

 

[D.A.(Tony)Stewart]

Like I said, it is open source

https://www.schneier.com/blowfish-download.html

 

[FvM]

I guess, the problem is that the OP don't want to translate the C code to Matlab himself.

 

[klun]

If I do change C++ to Matlab, does that involve a lot of changes in the body of the algorithm itself? Or only involving the syntax?

- - - Updated - - -

For example, this C code below. Is there any method to implement it in Matlab environment?

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Code C - [expand]
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#ifdef little_endian   /* Eg: Intel */
   #include <dos.h>
   #include <graphics.h>
   #include <io.h>
#endif
 
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
 
#ifdef little_endian   /* Eg: Intel */
   #include <alloc.h>
#endif
 
#include <ctype.h>
 
#ifdef little_endian   /* Eg: Intel */
   #include <dir.h>
   #include <bios.h>
#endif
 
#ifdef big_endian
   #include <Types.h>
#endif
 
#include "Blowfish.h"
 
#define N               16
#define noErr            0
#define DATAERROR         -1
#define KEYBYTES         8
#define subkeyfilename   "Blowfish.dat"
 
unsigned long P[N + 2];
unsigned long S[4][256];
FILE*         SubkeyFile;
 
short opensubkeyfile(void) /* read only */
{
   short error;
 
   error = noErr;
 
   if((SubkeyFile = fopen(subkeyfilename,"rb")) == NULL) {
      error = DATAERROR;
   }
 
   return error;
}
 
unsigned long F(unsigned long x)
{
   unsigned short a;
   unsigned short b;
   unsigned short c;
   unsigned short d;
   unsigned long  y;
 
   d = x & 0x00FF;
   x >>= 8;
   c = x & 0x00FF;
   x >>= 8;
   b = x & 0x00FF;
   x >>= 8;
   a = x & 0x00FF;
   //y = ((S[0][a] + S[1][b]) ^ S[2][c]) + S[3][d];
   y = S[0][a] + S[1][b];
   y = y ^ S[2][c];
   y = y + S[3][d];
 
   return y;
}
 
void Blowfish_encipher(unsigned long *xl, unsigned long *xr)
{
   unsigned long  Xl;
   unsigned long  Xr;
   unsigned long  temp;
   short          i;
 
   Xl = *xl;
   Xr = *xr;
 
   for (i = 0; i < N; ++i) {
      Xl = Xl ^ P[i];
      Xr = F(Xl) ^ Xr;
 
      temp = Xl;
      Xl = Xr;
      Xr = temp;
   }
 
   temp = Xl;
   Xl = Xr;
   Xr = temp;
 
   Xr = Xr ^ P[N];
   Xl = Xl ^ P[N + 1];
  
   *xl = Xl;
   *xr = Xr;
}
 
void Blowfish_decipher(unsigned long *xl, unsigned long *xr)
{
   unsigned long  Xl;
   unsigned long  Xr;
   unsigned long  temp;
   short          i;
 
   Xl = *xl;
   Xr = *xr;
 
   for (i = N + 1; i > 1; --i) {
      Xl = Xl ^ P[i];
      Xr = F(Xl) ^ Xr;
 
      /* Exchange Xl and Xr */
      temp = Xl;
      Xl = Xr;
      Xr = temp;
   }
 
   /* Exchange Xl and Xr */
   temp = Xl;
   Xl = Xr;
   Xr = temp;
 
   Xr = Xr ^ P[1];
   Xl = Xl ^ P[0];
 
   *xl = Xl;
   *xr = Xr;
}
 
short InitializeBlowfish(char key[], short keybytes)
{
   short          i;
   short          j;
   short          k;
   short          error;
   short          numread;
   unsigned long  data;
   unsigned long  datal;
   unsigned long  datar;
 
   /* First, open the file containing the array initialization data */
   error = opensubkeyfile();
   if (error == noErr) {
      for (i = 0; i < N + 2; ++i) {
     numread = fread(&data, 4, 1, SubkeyFile);
   #ifdef little_endian      /* Eg: Intel   We want to process things in byte   */
               /*   order, not as rearranged in a longword          */
     data = ((data & 0xFF000000) >> 24) |
        ((data & 0x00FF0000) >>  8) |
        ((data & 0x0000FF00) <<  8) |
        ((data & 0x000000FF) << 24);
   #endif
 
     if (numread != 1) {
        return DATAERROR;
     } else {
        P[i] = data;
     }
      }
 
      for (i = 0; i < 4; ++i) {
     for (j = 0; j < 256; ++j) {
         numread = fread(&data, 4, 1, SubkeyFile);
 
   #ifdef little_endian      /* Eg: Intel   We want to process things in byte   */
               /*   order, not as rearranged in a longword          */
        data = ((data & 0xFF000000) >> 24) |
           ((data & 0x00FF0000) >>  8) |
           ((data & 0x0000FF00) <<  8) |
           ((data & 0x000000FF) << 24);
   #endif
 
         if (numread != 1) {
           return DATAERROR;
        } else {
           S[i][j] = data;
        }
     }
      }
 
      fclose(SubkeyFile);
 
      j = 0;
      for (i = 0; i < N + 2; ++i) {
     data = 0x00000000;
     for (k = 0; k < 4; ++k) {
        data = (data << 8) | key[j];
        j = j + 1;
        if (j >= keybytes) {
           j = 0;
        }
     }
     P[i] = P[i] ^ data;
      }
 
    datal = 0x00000000;
      datar = 0x00000000;
 
      for (i = 0; i < N + 2; i += 2) {
     Blowfish_encipher(&datal, &datar);
 
     P[i] = datal;
     P[i + 1] = datar;
      }
 
      for (i = 0; i < 4; ++i) {
     for (j = 0; j < 256; j += 2) {
 
        Blowfish_encipher(&datal, &datar);
   
        S[i][j] = datal;
        S[i][j + 1] = datar;
     }
      }
   } else {
      printf("Unable to open subkey initialization file : %d\n", error);
   }
 
   return error;
}

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[FvM]

Basically, the code can be translated line by line. Besides usual control structures, there are integer XOR and AND operations, bitshifts and modular additions. If you review the TEA example linked in post #3, you get an idea how teh operations can be implemented in Matlab.