/**
* Retrieves a secret message from the specified BMP. The secret message is
* stored in an output file if specified, otherwise it is written to the
* console.
*
* @param courier a BMP image which contains a secret message
* @param output an optional output text file where the secret message is stored
*/
void Steg::decrypt(const std::string &courier, const std::string output)
{
std::vector<char> modifiedBytes;
read(modifiedBytes, courier);
std::string payload = "";
if (extractPayload(payload, modifiedBytes))
{
if (output == "")
{
std::cout << payload << std::endl;
}
else
{
std::ofstream outFile(output);
if (outFile.is_open() && !outFile.fail())
{
outFile.write(payload.c_str(), payload.length());
}
else
{
throw std::runtime_error("Output file failed to open, abort.");
}
}
}
else
{
std::string msg = "Input image is not encrypted!\n";
msg += "A non-ASCII character was found.";
throw std::runtime_error(msg);
}
}
/**
* Analyzes the a BMP file to allow the user to plan their message length
* appropriately.
*
* @param image the name of the image to analyze
*/
void Steg::analyze(const std::string &image)
{
std::vector<char> bytes;
read(bytes, image);
const unsigned int dWord =
bytes.at(0) << 24 |
bytes.at(1) << 16 |
bytes.at(2) << 8 |
bytes.at(3);
auto header = getHeaderSize(bytes);
unsigned short imageType = 0;
switch (header)
{
case 10:
imageType = 1;
break;
case 16:
imageType = 2;
break;
case 54:
imageType = 3;
break;
case 122:
imageType = 4;
break;
default:
imageType = -1;
break;
}
std::cout << " Analyzing \"" << image << "\"" << std::endl;
std::cout << " Image size : " << bytes.size() << " bytes\n";
std::cout << " Header size: " << header << " bytes" << std::endl;
std::cout << " BMP type : " << imageType << std::endl;
std::cout << " Max payload: "
<< ((bytes.size() - getHeaderSize(bytes)) / 8) - 1
<< " characters\n";
bool encrypted = true;
std::string payload;
if (!extractPayload(payload, bytes))
{
encrypted = false;
}
std::cout << " This image ";
if (encrypted)
{
std::cout << "may be ";
}
else
{
std::cout << "is probably not ";
}
std::cout << "encrypted.\n";
}
struct BPTC1969 decodeBPTC1969(bool bits[264]){
bool *infoBits; //196 info bits
bool *deInterleavedBits; //196 bits
static bool *payloadBits; //96 bits
int blocksToFollow=0,a;
unsigned char dpf=0,sap=0,bitPadding=0;
struct BPTC1969 BPTC1969decode;
infoBits = extractInfo(bits);
deInterleavedBits = deInterleave(infoBits);
payloadBits = extractPayload(deInterleavedBits);
/*printf("Payload bits\n");
for(a=0;a<96;a++){
printf("%i",*(payloadBits+a));
}
printf("\n");*/
if(*(payloadBits+1) == 1){
BPTC1969decode.responseRequested = true;
//syslog(LOG_NOTICE,"response requested");
}
else{
BPTC1969decode.responseRequested = false;
//syslog(LOG_NOTICE,"NO response requested");
}
for(a=4;a<8;a++){
if(*(payloadBits + a) == true) dpf = dpf + (char)(8 / pow(2,a-4));
}
//syslog(LOG_NOTICE,"Data Packet Format: ");
BPTC1969decode.dataPacketFormat = dpf;
switch (dpf){
case 0:
//syslog(LOG_NOTICE,"Unified Data Transport\n");
break;
case 1:
//syslog(LOG_NOTICE,"Response packet\n");
break;
case 2:
//syslog(LOG_NOTICE,"Data packet with unconfirmed delivery\n");
break;
case 3:
//syslog(LOG_NOTICE,"Data packet with confirmed delivery\n");
break;
case 13:
//syslog(LOG_NOTICE,"Short Data: Defined\n");
break;
case 14:
//syslog(LOG_NOTICE,"Short Data: Raw or Status/Precoded\n");
break;
case 15:
//syslog(LOG_NOTICE,"Proprietary Data Packet\n");
break;
}
for(a=8;a<12;a++){
if(*(payloadBits + a) == true) sap = sap + (char)(8 / pow(2,a-8));
}
//syslog(LOG_NOTICE,"SAP id: ");
BPTC1969decode.sapId = sap;
switch (sap){
case 0:
//syslog(LOG_NOTICE,"Unified Data Transport\n");
break;
case 2:
//syslog(LOG_NOTICE,"TCP/IP header compression\n");
break;
case 3:
//syslog(LOG_NOTICE,"UDP/IP header compression\n");
break;
case 4:
//syslog(LOG_NOTICE,"IP based Packet data\n");
break;
case 5:
//syslog(LOG_NOTICE,"Address Resolution Protocol(ARP)\n");
break;
case 9:
//syslog(LOG_NOTICE,"Proprietary Packet data\n");
break;
case 10:
//syslog(LOG_NOTICE,"Short Data\n");
break;
}
if (dpf == 13){
for(a=12;a<16;a++){//only AB in 2nd octet
if(*(payloadBits + a) == true) blocksToFollow = blocksToFollow + (char)(8 / pow(2,a-12));
}
BPTC1969decode.appendBlocks = blocksToFollow;
//syslog(LOG_NOTICE,"Appended blocks : %i\n",blocksToFollow);
for(a=72;a<80;a++){
if(*(payloadBits + a) == true) bitPadding = bitPadding + (char)(128 / pow(2,a-12));
}
}
return BPTC1969decode;
}
