Secure Client-Server Communication with Encryption Techniques

Posted on Jan 5, 2025 in Computers

int connectToServer(const char* ip, int port) { CLIENT 13
int sock = socket(AF_INET, SOCK_STREAM, 0);
struct sockaddr_in addr = {AF_INET, htons(port), inet_addr(ip)};
if (connect(sock, (struct sockaddr *) &addr, sizeof(addr)) < 0) {
cout << “\nRun server program first.” << endl;
exit(0); }
else
cout << “\nClient is connected to Server.” << endl;
return sock; }
int randInRange(int low, int high) {
return (rand() % (high – (low + 1))) + (low + 1); }
long powermod(long a, long b, long q) {
long res = 1;
for (long i = 0; i < b; i++)
res = (res * a) % q;
return res; }
int main() {
char ip[50];
cout << “\nEnter server’s IP address: “; cin >> ip;
int port; cout << “Enter port: “;
cin >> port;
int sock = connectToServer(ip, port);
long q, alpha;
cout << “\nEnter a prime number, q: “;
cin >> q;
cout << “Enter primitive root of q, alpha: “;
cin >> alpha;
srand(time(NULL));
long Xc = randInRange(1, q);
cout << “\nClient’s private key, Xc = ” << Xc << endl;
long Yc = powermod(alpha, Xc, q);
send(sock, &Yc, sizeof(Yc), 0);
cout << “Client’s public key, Yc = ” << Yc << endl;

string GenKey() { 3rd
string alpha = “abcdefghijklmnopqrstuvwxyz”;
string key = “abcdefghijklmnopqrstuvwxyz”;
random_device rd;
shuffle(key.begin(), key.end(), rd);
cout << “\nAlphabets: ” << alpha;
cout << “\nKey generated: ” << key;
return key; }
void MapKey(unordered_map &enKeyMap, unordered_map &deKeyMap, string key) {
string alpha = “abcdefghijklmnopqrstuvwxyz”;
for (int i = 0; i < 26; i++) {
enKeyMap[alpha[i]] = key[i];
deKeyMap[key[i]] = alpha[i]; } }
string Encrypt(string pText, unordered_map enKeyMap) {
string cText = “”;
for (int i = 0; i < pText.length(); i++) {
cText += enKeyMap[pText[i]]; }
return cText; }
void Decrypt(string &cText, unordered_map deKeyMap) {
cout << “After decryption: “;
for (int i = 0; i < cText.length(); i++) {
cout << deKeyMap[cText[i]]; }
cout << endl; }
void ShowFrequency(string pText, unordered_map enKeyMap) {
float fTable[26] = {0.000};
for (int i = 0; i < pText.length(); i++) {
fTable[pText[i] – ‘a’]++; }
cout << endl << “Frequency \t Plain Char \t Cipher Char” << endl;
for (int i = 0; i < pText.length(); i++) {
cout << fixed << setprecision(3) << (fTable[pText[i] – ‘a’] / pText.length()) << “\t\t ” << pText[i] << “\t\t ” << enKeyMap[pText[i]] << endl; } }

4th continuation

for (int i = 0; i < key.length(); i++) {
newkey += to_string(sortkey.find(key[i]) + 1); }
return newkey;
}
int main() {
int n;
cout << “Enter the value of n: “;
cin >> n;
string plaintext, key, k, ciphertext, decryptext;
cout << “Enter text: “;
cin >> plaintext;
cout << “Enter key: “;
cin >> k;
key = format(k);
int i = 1;
while (n > 0) {
cout << “LEVEL ” << i << endl;
ciphertext = encrypt(plaintext, key);
plaintext = ciphertext;
n–;
i++; }
n = i – 1, i = 1;
while (n > 0) {
cout << “LEVEL ” << i << endl;
decryptext = decrypt(ciphertext, key);
ciphertext = decryptext;
n–;
i++; }
return 0; }

string encrypt(string pt, string key) { 4th
string ct = “”;
int cols = key.length();
while (pt.length() % cols != 0) pt += ‘x’;
int rows = pt.length() / cols;
char mat[rows][cols];
int k = 0;
cout << “\nEncryption Matrix:” << endl;
for (int i = 0; i < rows; i++) {
for (int j = 0; j < cols; j++) {
cout << (mat[i][j] = pt[k++]) << ” “; }
cout << endl; }
for (int i = 0; i < cols; i++) {
for (int j = 0; j < rows; j++)
ct += mat[j][key.find(i + ‘1’)]; }
cout << “\nEncrypted text: ” << ct << endl;
return ct; }

string decrypt(string ct, string key) {
string pt = “”;
int cols = key.length();
int rows = ct.length() / cols;
char mat[rows][cols];
int k = 0;
for (int i = 0; i < cols; i++) {
for (int j = 0; j < rows; j++) {
mat[j][key.find(i + ‘1’)] = ct[k++]; } }
cout << “\nDecryption Matrix:” << endl;
for (int i = 0; i < rows; i++) {
for (int j = 0; j < cols; j++) {
cout << mat[i][j] << ” “;
pt += mat[i][j]; }
cout << endl; }
cout << “\nDecrypted text: ” << pt << endl;
return pt; }

string format(string key) {

string sortkey = key, newkey = “”;
sort(sortkey.begin(), sortkey.end());

int main() {
unsigned long long key;
cout << endl << “Enter 64 bit key in hexadecimal 16 digits: “;
cin >> hex >> key;
string binarykey = bitset<64>(key).to_string();
cout << endl << “Binary key: ” << binarykey << endl;
binarykey = firstPermute(binarykey);
cout << endl << “PC-1 key (k+): ” << binarykey << endl << endl;
gen_keys(binarykey.substr(0, 28), binarykey.substr(28, 28));
return 0;
}

int main() {
unsigned long long hexa, key_hex;
string binary;
cout << “Enter the 16 bit hexadecimal input:” << endl;
cin >> hex >> hexa;
binary = bitset<64>(hexa).to_string();
string key;
cout << “Enter the 12 bit hexadecimal key:” << endl;
cin >> hex >> key_hex;
key = bitset<48>(key_hex).to_string();
cout << “\nRound Function\n” << endl;
string left = binary.substr(0, 32);
string right = binary.substr(32, 32);
string expRight = expansion(right, ETable);
cout << “After expansion, right half will be: ” << expRight << endl;
cout << “Key is: ” << (key) << endl;
string sb_ip = xor_operation(expRight, key);
cout << “S-box operation\n”;
cout << “The 48 bit input for S-box will be: ” << sb_ip << endl;
string sBoxOutput = substitution(sb_ip);
cout << “\nS-Box output = ” << sBoxOutput << endl;
string P = permute(sBoxOutput);
cout << “Permuted output = ” << P << endl;
string Ri = xor_operation(P, left);
cout << “\nOutput of ith round (Ri) = ” << Ri << endl << endl;
return 0; }

string expansion(string ip, int *Etable) {
string res = “”;
for (int i = 0; i < 48; i++)
res += ip[Etable[i] – 1];
return res;
}

int main() {
unsigned long long hexkey1, hexkey2;
cout << endl << “\nEnter first 64-bit key in hexadecimal (16-digits): “;
cin >> hex >> hexkey1;
cout << endl << “\nEnter next 64-bit key in hexadecimal (16-digits): “;
cin >> hex >> hexkey2;
string key = bitset<64>(hexkey1).to_string() + bitset<64>(hexkey2).to_string();
cout << endl << “Binary key (k): ” << key << endl;
cout << endl << “keyLen: ” << key.length() << endl << endl;
for (int i = 0; i < 4; i++) {
w[i] = key.substr(i * 32, 32); }
for (int i = 4; i < 44; i++) {
string first = w[i – 4];
string second = w[i – 1];
if (i % 4 == 0) {
second = rotLeft(second);
second = SBoxFun(second);
string tmp = bitset<32>(Rcon[i / 4 – 1]).to_string();
second = XOR(second, tmp); } }

int main() {
string plaintext;
cout << “Enter message: “;
cin >> plaintext;
string key;
cout << “\nEnter key: “;
cin >> key;
int n = plaintext.length();
int pt[256];
cout << “Plain text: “;
for (int i = 0; i < n; i++) {
pt[i] = (int)plaintext[i];
cout << pt[i] << ” “; }
int S[256], T[256];
for (int i = 0; i < 256; i++) {
S[i] = i;
T[i] = (int)key[i % key.length()]; }
int j = 0;
for (int i = 0; i < 256; i++) {
j = (j + S[i] + T[i]) % 256;
swap(S[i], S[j]); }
int keyStream[256];
cout << “\nKey Stream: “;
j = 0;
for (int i = 0; i < n; i++) {
j = (j + S[i]) % 256;
swap(S[i], S[j]);
int t = (S[i] + S[j]) % 256;
keyStream[i] = S[t];
cout << keyStream[i] << ” “; }
int ct[256];
cout << “\n\nENCRYPTION” << endl;
cout << “Cipher Text: “;
for (int i = 0; i < n; i++) {
ct[i] = pt[i] ^ keyStream[i]; // xor
cout << ct[i] << ” “; }