103 lines
2.8 KiB
C++
103 lines
2.8 KiB
C++
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#include <iostream>
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#include <cstring>
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using namespace std;
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string XOR(string data, string key) {
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// Dividend is data
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// Divisor is the primary key, i.e. the key
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string result = "";
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int dataLen = data.length();
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int keyLen = key.length();
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// Perform XOR operation
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for (int i=0; i<keyLen; i++) {
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if (i < dataLen) {
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// Only perform XOR if within the length of data
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if (data[i] == key[i]) {
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result += '0';
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}
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else {
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result += '1';
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}
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} else {
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// If data length exceeded, append the key
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result += key[i];
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}
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}
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return result;
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}
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string encoder(string data, string key) {
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int keyLen = key.length();
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// Append n-1 zeroes to the data
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string dataWithZeroes = data + string(keyLen-1, '0');
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// Perform XOR operation with the key
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string remainder = XOR(dataWithZeroes, key);
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// Get the remainder (last n-1 bits)
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string crc = remainder.substr(remainder.length() - (keyLen-1));
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// Append the CRC to the original data
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return data + crc;
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}
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string performDivision(string data, string key) {
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int keyLen = key.length();
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// Initialize with the data to be divided
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string temp = data.substr(0, keyLen);
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// Perform XOR operations on each segment
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for (int i = keyLen; i < data.length(); i++) {
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if (temp[0] == '1') { // Only perform XOR if the leading bit is 1
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temp = XOR(temp, key);
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}
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temp = temp.substr(1) + data[i]; // Shift left and add the next bit
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}
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// Perform the final XOR operation
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if (temp[0] == '1') {
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temp = XOR(temp, key);
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}
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// Extract the remainder (last keyLen-1 bits)
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return temp.substr(temp.length() - (keyLen - 1));
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}
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// Function to check the correctness of received data
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bool checkData(string data, string key) {
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string remainder = performDivision(data, key);
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return (remainder.find('1') == string::npos); // No '1' means remainder is all zeros
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}
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int main() {
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string data, key;
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cout << endl << "Enter data:\t";
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getline(cin, data);
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cout << "Enter primary key:\t";
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getline(cin, key);
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cout<<endl<<"Original data:\t"<<data;
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cout<<endl<<"Key:\t"<<key;
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string messageToSend = encoder(data, key);
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cout<<endl<<"----------------------------------------"<<endl;
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cout<<"Message to be sent:\t"<<messageToSend;
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cout<<endl<<"----------------------------------------"<<endl;
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string receivedData;
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cout<<endl<<"HINT: Received data should be the same as message to be sent.";
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cout<<endl<<"Enter received data:\t";
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getline(cin, receivedData);
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if (receivedData == messageToSend) {
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cout<<"The received data is correct."<<endl;
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} else {
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cout<<"The received data appears to be tampered."<<endl;
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}
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return 0;
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}
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