Thread: AES encryption and decryption not going over whole array

Hey guys the code takes in a string,converts it into a hex decimal string and puts it into an array (52 bytes) and is then encrypted in 16 byte fragments and then goes over all 52 and decrypts them. Now it only seems to encrypt and decrypt parts and leaves out parts. Please help Code:

Code:

string sensorinfo = "0 1.345000 80.000000 100.000000 Temperature,Constant";
cout << sensorinfo;
stringstream str1;
for (int i = 0; i < sensorinfo.length(); i++) {
  str1 << std::hex << (int) sensorinfo.at(i);
}

cout << sensorinfo;
cout << str1.str() << "\n";
int w, l;

const std::string tmp = str1.str();
std::string temp;

for (int w = 0; w < tmp.length(); w++)
{
temp += tmp.at(w);

}

int length = temp.size();
string output = "";

//for each block of 2 characters
for (int i = 0; i < length; i = i + 2) {
  //copy 2 characters and a space to the output
  output += temp.substr(i, 2) + " ";

}

// partition data into 16 byte blocks before encryption 

int q;
std::istringstream hex_chars_stream(output);
std::vector < unsigned char >bytes;
unsigned char databytes[52];    // 52 data bytes
unsigned char fragmentbytes[16];
unsigned char encrypteddata[52];
unsigned int c;
while (hex_chars_stream >> std::hex >> c) {
  bytes.push_back(c);

}

cout << "The size of the vector is:" << bytes.size();

for (q = 0; q < 51; q++) {
  databytes[q] = bytes[q];
  //cout << "databytes7 data: " << databytes[q];
}

for (q = 0; q < 52; q++) {      // This loop doesn't work without the above one??
  databytes[q] = bytes[q];
  //cout << "databytes8 data: " << databytes[q];
}

cout << "Before encryption";
for (i = 0; i <= 51; i++) {
  cout << databytes[i];
}

int ff, gg, hh, ik;

for (hh = 0; hh < 16; hh++) {
  ff++;
  fragmentbytes[hh] = databytes[ff];
}

cout << "The value of ff is:" << ff;
aes_encrypt(fragmentbytes, key);
int k;
cout << "After encryption";
for (k = 0; k <= 15; k++) {
  encrypteddata[k] = fragmentbytes[k];
  trace() << hex << fragmentbytes[k];
}

for (hh = 0; hh < 16; hh++) {
  fragmentbytes[hh] = 0;

}

while (ff < 52) {

  for (hh = 0; hh < 16; hh++) {

    fragmentbytes[hh] = databytes[ff];
    ff++;
  }
  cout << "The value of ff is:" << ff;
  ff - 16;                      // to be able to put the same data from fragmentbytes into encrypteddata 
  aes_encrypt(fragmentbytes, key);
  int k;
  cout << "After encryption";
  for (k = 0; k <= 15; k++) {
    cout << hex << fragmentbytes[k];
    encrypteddata[ff] = fragmentbytes[k];
    ff++;
  }
  for (hh = 0; hh < 16; hh++) {
    fragmentbytes[hh] = 0;

  }
}

//decryption
ff = 0;
for (hh = 0; hh < 16; hh++) {

  fragmentbytes[hh] = encrypteddata[ff];
  ff++;
}

cout << "The value of ff is:" << ff;
ff - 16;
aes_decrypt(fragmentbytes, key);
int io;
cout << "After decryption";
for (io = 0; io <= 15; io++) {
  cout << hex << (int) fragmentbytes[io];
  encrypteddata[ff] = fragmentbytes[io];
  ff++;
}

for (hh = 0; hh < 16; hh++) {
  fragmentbytes[hh] = 0;

}

while (ff < 52) {

  for (hh = 0; hh < 16; hh++) {

    fragmentbytes[hh] = encrypteddata[ff];
    ff++;
  }
  cout << "The value of ff is:" << ff;
  ff - 16;
  aes_decrypt(fragmentbytes, key);
  int k;
  cout << "After decryption";
  for (k = 0; k <= 15; k++) {
    cout << hex << (int) fragmentbytes[k];
    encrypteddata[ff] = fragmentbytes[k];
    ff++;
  }
  for (hh = 0; hh < 16; hh++) {
    fragmentbytes[hh] = 0;

  }
}

Have you tried running the code in a debugger?
Now is a good time to start practising.

In particular, you might want to breakpoint on ff - 16; and decide if it does what you think it does.

Finally, next time you post, make sure you either 'copy as text' or 'paste as text'.

Your code is massively over-complicated.
You didn't show the aes_encrypt or aes_decrypt function so I just made a simple one as an example (just adds the "key", which I set to 1).

Code:

#include <iostream>
#include <iomanip>
#include <string>
#include <vector>
using namespace std;
 
void print16(const unsigned char *buf) {
    cout << hex << setfill('0');
    for (size_t i = 0; i < 16; i++)
        cout << setw(2) << (int)buf[i] << ' ';
    cout << '\n';
}
 
void aes_encrypt(unsigned char *buf, int key) {
    for (size_t i = 0; i < 16; i++)
        buf[i] += key;
}
 
int main() {
    string info = "0 1.345000 80.000000 100.000000 Temperature,Constant";
 
    vector<unsigned char> bytes(info.begin(), info.end());
 
    // Ensure bytes size is a multiple of 16.
    bytes.resize(bytes.size() + (16-bytes.size()%16)%16, ' ');
 
    int key = 1;
    for (size_t i = 0; i < bytes.size(); i += 16) {
        aes_encrypt(bytes.data() + i, key);
        print16(bytes.data() + i);
    }
}