sender.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "common.h"
#include "ipc.h"
#include "encryption.h"
#include "integrity.h"
#include "keygen.h"

int main() {
    int shmid, semid;
    struct shared_data *data;
    char plaintext[MAX_MESSAGE_SIZE];
    uint8_t ciphertext[MAX_MESSAGE_SIZE];
    char master_key[MASTER_KEY_LEN + 1];
    char enc_key[DERIVED_KEY_LEN + 1];
    char hash_key[DERIVED_KEY_LEN + 1];
    unsigned char hash[HASH_SIZE];

    printf("=== SENDER: Secure Message Transmission ===\n\n");

    // Get master key from user
    printf("Enter master key: ");
    fgets(master_key, sizeof(master_key), stdin);
    master_key[strcspn(master_key, "\n")] = 0;  // Remove newline

    // Pad or truncate to exact length
    int key_len = strlen(master_key);
    if (key_len < MASTER_KEY_LEN) {
        // Pad with zeros if too short
        for (int i = key_len; i < MASTER_KEY_LEN; i++) {
            master_key[i] = '0';
        }
        master_key[MASTER_KEY_LEN] = '\0';
    } else if (key_len > MASTER_KEY_LEN) {
        // Truncate if too long
        master_key[MASTER_KEY_LEN] = '\0';
    }

    // Derive encryption and hashing keys from master key
    derive_keys(master_key, enc_key, hash_key);

    printf("Key received! Preparing secure channel...\n");
    printf("\n--- Backend Key Information ---\n");
    printf("Encryption Key: %s\n", enc_key);
    printf("Hash Key: %s\n", hash_key);
    printf("-------------------------------\n\n");

    // Create or get shared memory and semaphore
    shmid = create_shared_memory();
    semid = create_semaphore();
    data = attach_shared_memory(shmid);

    // Get message from user
    printf("Enter message to send: ");
    fgets(plaintext, MAX_MESSAGE_SIZE, stdin);
    plaintext[strcspn(plaintext, "\n")] = 0;  // Remove newline

    int len = strlen(plaintext);

    // Encrypt the message
    hybrid_encrypt((uint8_t*)plaintext, ciphertext, len, (uint8_t*)enc_key, strlen(enc_key));

    // Display encrypted text in hex format
    printf("\n--- Encrypted Text (Hex) ---\n");
    printf("Plaintext: %s\n", plaintext);
    printf("Ciphertext: ");
    for (int i = 0; i < len; i++) {
        printf("%02x", ciphertext[i]);
    }
    printf("\n----------------------------\n");

    // Generate hash for integrity verification
    key_mixed_rolling_hash((char*)ciphertext, len, hash_key, hash, HASH_SIZE);
    to_hex(hash, HASH_SIZE, data->hash);

    printf("\n--- Integrity Hash (Hex) ---\n");
    printf("Generated Hash: %s\n", data->hash);
    printf("----------------------------\n\n");

    // Wait for semaphore (lock)
    printf("Encrypting and sending message...\n");
    semaphore_wait(semid);

    // Write to shared memory
    memcpy(data->message, ciphertext, len);
    data->message_length = len;
    data->ready = 1;

    // Signal semaphore (unlock)
    semaphore_signal(semid);

    // Wait for receiver to consume the message
    printf("Waiting for receiver...\n");
    while (data->ready == 1) {
        sleep(1);
    }

    printf("\nMessage delivered successfully!\n");

    // Cleanup
    detach_shared_memory(data);

    printf("\n=== SENDER: Transmission Complete ===\n");

    return 0;
}