Hide a file in a BMP file (Plus).

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• Download demo project - 216 Kb

Introduction

After I read the article 'Hiding a text file in a BMP file', I found it very funny, and maybe useful. So I decided to extend it to fit in with any file, any password, and become easy to use.

Background

You can find its principle here: Hiding a text file in a BMP file. Very thanks to Ahmed Osama's idea and good work.

Class Structure

class CBmpHermitCrab
{
 ...
public:
 bool Hermit(const char* pszDestFileName, 
  const char* pszSrcFileName,
  const char* pszPassword=NULL, 
  const char* pszResultFile=NULL); 
 bool IsHermitCrabBMPFile(const char* pszFileName);
 bool RecoverCrabFile(const char* pszFileName, 
  const char* pszPassword=NULL, const char* pszPath=NULL);
};

It provides three methods to implement the following tasks:

1. Hermit(). Hides a file in a BMP file.

   The main code:

   ...
    nIndex=0;
     for(int i=0;i<(iBinaryLen/8); i++){
        temp= m_binaryMap[(unsigned char) strBufferAll[i]];
        srcBinary[nIndex] = temp[0];
        srcBinary[nIndex+1] =temp[1];
        srcBinary[nIndex+2] =temp[2];
        srcBinary[nIndex+3] =temp[3];
        srcBinary[nIndex+4] =temp[4];
        srcBinary[nIndex+5] =temp[5];
        srcBinary[nIndex+6] =temp[6];
        srcBinary[nIndex+7] =temp[7];
        nIndex=nIndex+8; 
     }
   
     int mask=254; 
     for (i=0 ; i<iBinaryLen ; i++){
         bmpBuffer[i+55]=bmpBuffer[i+55] & mask;
         if (srcBinary[i]=='1')  
           bmpBuffer[i+55]=bmpBuffer[i+55]+1;
     }
    ...

   Through our binary table srcBinary and the correct index, we can express a char by using the original pixel color value micro-changed.

2. RecoverCrabFile(). Recovers hidden file from a HermitCrab ;) BMP file.

   The key code:

   ...
    for(j=55+8*nHeadSize; j < 55+8*nHeadSize 
      +pHermitCrabHead->bPasswordLen*8+
      pHermitCrabHead->bFileNameLen*8;j++){
         recBin[j]= 
          (unsigned char) ((unsigned char)buffer[j] & 1);
    }
    CString strTemp;
    for(j=55+8*nHeadSize; j < 
      55+8*nHeadSize+pHermitCrabHead->bPasswordLen*8+
      pHermitCrabHead->bFileNameLen*8;j=j+8){
         temp=128*recBin[j]+64*recBin[j+1]+32*recBin[j+2]+
             16*recBin[j+3]+8*recBin[j+4]+4*recBin[j+5]+
             2*recBin[j+6]+1*recBin[j+7];
       strTemp+=temp;
    } 
   ...

3. IsHermitCrabBMPFile(). Like method 2, but it just recovers the fist 8 bytes, and whether the first two bytes: 'C' and 'H'.

Using the code

1. Include the BmpHermitCrab.h file.
2. Generate a CBmpHermitCrab instance.
3. With the instance, use the Hermit() method to hide a file in a BMP file with optional password and use the RecoverCrabFile() method to recover a file from a 'HermitCrab' BMP file. You can check the BMP file format by IsHermitCrabBMPFile() method.

Hope you enjoy the program!