/* secure_channel.c - Secure Channel library implementation using TinyCrypt or OpenSSL */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include "secure_channel.h"
#include "../lib/debug_config.h"
#include <string.h>
#include <stddef.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/time.h>
#include <stdio.h>
#include <fcntl.h>
#include "crc32.h"
#include "../lib/sha256.h"

// To switch between implementations, define USE_OPENSSL before including/compiling.
// If USE_OPENSSL is defined, use OpenSSL; otherwise, use TinyCrypt (original logic).
// The core logic (e.g., nonce building, CRC, session key derivation as memcpy, counters, etc.) remains unchanged.

#ifdef USE_OPENSSL
#include <openssl/evp.h>
#include <openssl/ec.h>
#include <openssl/rand.h>
#include <openssl/sha.h>
#include <openssl/err.h>
#else
#include "../tinycrypt/lib/include/tinycrypt/ecc.h"
#include "../tinycrypt/lib/include/tinycrypt/ecc_dh.h"
#include "../tinycrypt/lib/include/tinycrypt/aes.h"
#include "../tinycrypt/lib/include/tinycrypt/ccm_mode.h"
#include "../tinycrypt/lib/include/tinycrypt/constants.h"
#include "../tinycrypt/lib/include/tinycrypt/ecc_platform_specific.h"
#include "../tinycrypt/lib/include/tinycrypt/sha256.h"
#endif

static uint8_t sc_urandom_seed[8] = {0};
static int sc_urandom_initialized = 0;

static void sc_init_random_seed(void)
{
    int fd = open("/dev/urandom", O_RDONLY);
    if (fd >= 0) {
        ssize_t ret = read(fd, sc_urandom_seed, 8);
        close(fd);
        if (ret == 8) {
            sc_urandom_initialized = 1;
        }
    }
}

// Конвертация hex строки в бинарный формат (common)
static int hex_to_binary(const char *hex_str, uint8_t *binary, size_t binary_len) {
    if (!hex_str || !binary || strlen(hex_str) != binary_len * 2) return -1;
    
    for (size_t i = 0; i < binary_len; i++) {
        unsigned int byte;
        if (sscanf(hex_str + i * 2, "%2x", &byte) != 1) return -1;
        binary[i] = (uint8_t)byte;
    }
    return 0;
}

sc_status_t sc_init_ctx(sc_context_t *ctx, struct SC_MYKEYS *mykeys) {
    ctx->pk = mykeys;
    ctx->initialized = 1;
    ctx->peer_key_set = 0;
    ctx->session_ready = 0;
    ctx->tx_counter = 0;
    ctx->rx_counter = 0;
    return SC_OK;
}

#ifdef USE_OPENSSL

// OpenSSL-specific implementations

static int sc_rng(uint8_t *dest, unsigned size) {
    // OpenSSL has its own RNG, but for consistency with original, mix urandom + pid + time
    int fd = open("/dev/urandom", O_RDONLY);
    if (fd < 0) {
        return 0;
    }
    ssize_t ret = read(fd, dest, size);
    close(fd);
    if (ret != size) {
        return 0;
    }
    pid_t pid = getpid();
    struct timeval tv;
    gettimeofday(&tv, NULL);
    for (unsigned i = 0; i < size; i++) {
        dest[i] ^= ((pid >> (i % (sizeof(pid) * 8))) & 0xFF);
        dest[i] ^= ((tv.tv_sec >> (i % (sizeof(tv.tv_sec) * 8))) & 0xFF);
        dest[i] ^= ((tv.tv_usec >> (i % (sizeof(tv.tv_usec) * 8))) & 0xFF);
    }
    return 1;
}

static int sc_validate_key(const uint8_t *public_key) {
    EC_GROUP *group = EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1);
    if (!group) return -1;
    EC_POINT *point = EC_POINT_new(group);
    if (!point) {
        EC_GROUP_free(group);
        return -1;
    }
    BIGNUM *x = BN_bin2bn(public_key, 32, NULL);
    BIGNUM *y = BN_bin2bn(public_key + 32, 32, NULL);
    if (!x || !y || EC_POINT_set_affine_coordinates(group, point, x, y, NULL) != 1) {
        BN_free(x);
        BN_free(y);
        EC_POINT_free(point);
        EC_GROUP_free(group);
        return -1;
    }
    int result = EC_POINT_is_on_curve(group, point, NULL);
    BN_free(x);
    BN_free(y);
    EC_POINT_free(point);
    EC_GROUP_free(group);
    // To match TinyCrypt return convention in the provided code (0 valid, !=0 invalid)
    return (result == 1) ? 0 : -1;
}

sc_status_t sc_generate_keypair(struct SC_MYKEYS *pk) {
    if (!pk) {
        return SC_ERR_INVALID_ARG;
    }
    EC_GROUP *group = EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1);
    if (!group) return SC_ERR_CRYPTO;
    EC_KEY *key = EC_KEY_new();
    if (!key) {
        EC_GROUP_free(group);
        return SC_ERR_CRYPTO;
    }
    if (EC_KEY_set_group(key, group) != 1) {
        EC_KEY_free(key);
        EC_GROUP_free(group);
        return SC_ERR_CRYPTO;
    }
    // Use custom RNG if needed, but OpenSSL RAND is fine; for consistency, seed if necessary
    if (EC_KEY_generate_key(key) != 1) {
        EC_KEY_free(key);
        EC_GROUP_free(group);
        return SC_ERR_CRYPTO;
    }
    const BIGNUM *priv = EC_KEY_get0_private_key(key);
    if (BN_bn2binpad(priv, pk->private_key, SC_PRIVKEY_SIZE) != SC_PRIVKEY_SIZE) {
        EC_KEY_free(key);
        EC_GROUP_free(group);
        return SC_ERR_CRYPTO;
    }
    const EC_POINT *pub_point = EC_KEY_get0_public_key(key);
    uint8_t pub_buf[65];
    if (EC_POINT_point2oct(group, pub_point, POINT_CONVERSION_UNCOMPRESSED, pub_buf, 65, NULL) != 65) {
        EC_KEY_free(key);
        EC_GROUP_free(group);
        return SC_ERR_CRYPTO;
    }
    memcpy(pk->public_key, pub_buf + 1, SC_PUBKEY_SIZE);  // Skip 0x04 prefix
    EC_KEY_free(key);
    EC_GROUP_free(group);
    return SC_OK;
}

sc_status_t sc_init_local_keys(struct SC_MYKEYS *mykeys, const char *public_key, const char *private_key) {
    if (!mykeys || !public_key || !private_key) {
        DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_init_local_keys: invalid arguments");
        return SC_ERR_INVALID_ARG;
    }
    DEBUG_INFO(DEBUG_CATEGORY_CRYPTO, "sc_init_local_keys: public_key len=%zu, private_key len=%zu", 
               strlen(public_key), strlen(private_key));
    if (hex_to_binary(public_key, mykeys->public_key, SC_PUBKEY_SIZE)) {
        DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_init_local_keys: failed to convert public key from hex");
        return SC_ERR_INVALID_ARG;
    }
    if (hex_to_binary(private_key, mykeys->private_key, SC_PRIVKEY_SIZE)) {
        DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_init_local_keys: failed to convert private key from hex");
        return SC_ERR_INVALID_ARG;
    }
    if (sc_validate_key(mykeys->public_key) != 0) {
        DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_init_local_keys: public key validation failed");
        return SC_ERR_INVALID_ARG;
    }
    DEBUG_INFO(DEBUG_CATEGORY_CRYPTO, "sc_init_local_keys: keys initialized successfully");
    return SC_OK;
}

sc_status_t sc_set_peer_public_key(sc_context_t *ctx, const char *peer_public_key_h, int mode) {
    uint8_t peer_public_key[SC_PUBKEY_SIZE];
    if (mode) {
        if (hex_to_binary(peer_public_key_h, peer_public_key, SC_PUBKEY_SIZE)) {
            DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_set_peer_public_key: invalid hex key format");
            return SC_ERR_INVALID_ARG;
        }
    } else {
        memcpy(peer_public_key, (const uint8_t *)peer_public_key_h, SC_PUBKEY_SIZE);
    }
    if (!ctx) {
        DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_set_peer_public_key: invalid ctx");
        return SC_ERR_INVALID_ARG;
    }
    if (!ctx->initialized) {
        DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_set_peer_public_key: ctx not initialized");
        return SC_ERR_NOT_INITIALIZED;
    }
    if (sc_validate_key(peer_public_key) != 0) {
        DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_set_peer_public_key: invalid key");
        return SC_ERR_INVALID_ARG;
    }
    if (!ctx->pk) {
        DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_set_peer_public_key: no private key");
        return SC_ERR_NOT_INITIALIZED;
    }
    EC_GROUP *group = EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1);
    if (!group) return SC_ERR_CRYPTO;
    EC_KEY *my_key = EC_KEY_new();
    if (!my_key) {
        EC_GROUP_free(group);
        return SC_ERR_CRYPTO;
    }
    if (EC_KEY_set_group(my_key, group) != 1) {
        EC_KEY_free(my_key);
        EC_GROUP_free(group);
        return SC_ERR_CRYPTO;
    }
    BIGNUM *my_priv = BN_bin2bn(ctx->pk->private_key, SC_PRIVKEY_SIZE, NULL);
    if (!my_priv || EC_KEY_set_private_key(my_key, my_priv) != 1) {
        BN_free(my_priv);
        EC_KEY_free(my_key);
        EC_GROUP_free(group);
        return SC_ERR_CRYPTO;
    }
    EC_POINT *peer_point = EC_POINT_new(group);
    if (!peer_point) {
        BN_free(my_priv);
        EC_KEY_free(my_key);
        EC_GROUP_free(group);
        return SC_ERR_CRYPTO;
    }
    BIGNUM *x = BN_bin2bn(peer_public_key, 32, NULL);
    BIGNUM *y = BN_bin2bn(peer_public_key + 32, 32, NULL);
    if (!x || !y || EC_POINT_set_affine_coordinates(group, peer_point, x, y, NULL) != 1) {
        BN_free(x);
        BN_free(y);
        BN_free(my_priv);
        EC_POINT_free(peer_point);
        EC_KEY_free(my_key);
        EC_GROUP_free(group);
        return SC_ERR_CRYPTO;
    }
    uint8_t shared_secret[SC_SHARED_SECRET_SIZE];
    int len = ECDH_compute_key(shared_secret, SC_SHARED_SECRET_SIZE, peer_point, my_key, NULL);
    if (len != SC_SHARED_SECRET_SIZE) {
        DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_set_peer_public_key: shared secret error");
        BN_free(x);
        BN_free(y);
        BN_free(my_priv);
        EC_POINT_free(peer_point);
        EC_KEY_free(my_key);
        EC_GROUP_free(group);
        return SC_ERR_CRYPTO;
    }
    memcpy(ctx->session_key, shared_secret, SC_SESSION_KEY_SIZE);
    memcpy(ctx->peer_public_key, peer_public_key, SC_PUBKEY_SIZE);
    ctx->peer_key_set = 1;
    ctx->session_ready = 1;
    BN_free(x);
    BN_free(y);
    BN_free(my_priv);
    EC_POINT_free(peer_point);
    EC_KEY_free(my_key);
    EC_GROUP_free(group);
    return SC_OK;
}

static void sc_build_nonce(uint64_t counter, uint8_t *nonce_out) {
    SHA256_CTX sha_ctx;
    uint8_t hash[32];
    struct timeval tv;
    uint8_t data[24];
    if (!sc_urandom_initialized) {
        sc_init_random_seed();
    }
    gettimeofday(&tv, NULL);
    memcpy(data, sc_urandom_seed, 8);
    data[8] = (counter >> 0) & 0xFF;
    data[9] = (counter >> 8) & 0xFF;
    data[10] = (counter >> 16) & 0xFF;
    data[11] = (counter >> 24) & 0xFF;
    data[12] = (counter >> 32) & 0xFF;
    data[13] = (counter >> 40) & 0xFF;
    data[14] = (counter >> 48) & 0xFF;
    data[15] = (counter >> 56) & 0xFF;
    data[16] = (tv.tv_sec >> 0) & 0xFF;
    data[17] = (tv.tv_sec >> 8) & 0xFF;
    data[18] = (tv.tv_sec >> 16) & 0xFF;
    data[19] = (tv.tv_sec >> 24) & 0xFF;
    data[20] = (tv.tv_usec >> 0) & 0xFF;
    data[21] = (tv.tv_usec >> 8) & 0xFF;
    data[22] = (tv.tv_usec >> 16) & 0xFF;
    data[23] = (tv.tv_usec >> 24) & 0xFF;
    SHA256_Init(&sha_ctx);
    SHA256_Update(&sha_ctx, data, 24);
    SHA256_Final(hash, &sha_ctx);
    memcpy(nonce_out, hash, SC_NONCE_SIZE);
}

sc_status_t sc_encrypt(sc_context_t *ctx, const uint8_t *plaintext, size_t plaintext_len, uint8_t *ciphertext, size_t *ciphertext_len) {
    if (!ctx || !plaintext || !ciphertext || !ciphertext_len) {
        return SC_ERR_INVALID_ARG;
    }
    if (!ctx->session_ready) {
        return SC_ERR_NOT_INITIALIZED;
    }
    if (plaintext_len == 0) {
        return SC_ERR_INVALID_ARG;
    }
    uint8_t plaintext_with_crc[plaintext_len + SC_CRC32_SIZE];
    memcpy(plaintext_with_crc, plaintext, plaintext_len);
    uint32_t crc = crc32_calc(plaintext, plaintext_len);
    plaintext_with_crc[plaintext_len] = (crc >> 0) & 0xFF;
    plaintext_with_crc[plaintext_len + 1] = (crc >> 8) & 0xFF;
    plaintext_with_crc[plaintext_len + 2] = (crc >> 16) & 0xFF;
    plaintext_with_crc[plaintext_len + 3] = (crc >> 24) & 0xFF;
    size_t total_plaintext_len = plaintext_len + SC_CRC32_SIZE;
    uint8_t nonce[SC_NONCE_SIZE];
    sc_build_nonce(ctx->tx_counter, nonce);
    EVP_CIPHER_CTX *ectx = EVP_CIPHER_CTX_new();
    if (!ectx) return SC_ERR_CRYPTO;
    if (EVP_EncryptInit_ex(ectx, EVP_aes_128_ccm(), NULL, NULL, NULL) != 1) {
        EVP_CIPHER_CTX_free(ectx);
        return SC_ERR_CRYPTO;
    }
    if (EVP_CIPHER_CTX_ctrl(ectx, EVP_CTRL_AEAD_SET_IVLEN, SC_NONCE_SIZE, NULL) != 1) {
        EVP_CIPHER_CTX_free(ectx);
        return SC_ERR_CRYPTO;
    }
    if (EVP_CIPHER_CTX_ctrl(ectx, EVP_CTRL_AEAD_SET_TAG, SC_TAG_SIZE, NULL) != 1) {
        EVP_CIPHER_CTX_free(ectx);
        return SC_ERR_CRYPTO;
    }
    if (EVP_EncryptInit_ex(ectx, NULL, NULL, ctx->session_key, nonce) != 1) {
        EVP_CIPHER_CTX_free(ectx);
        return SC_ERR_CRYPTO;
    }
    int outlen;
    uint8_t outbuf[total_plaintext_len];
    if (EVP_EncryptUpdate(ectx, outbuf, &outlen, plaintext_with_crc, total_plaintext_len) != 1 ||
        outlen != (int)total_plaintext_len) {
        EVP_CIPHER_CTX_free(ectx);
        return SC_ERR_CRYPTO;
    }
    int tmp;
    if (EVP_EncryptFinal_ex(ectx, outbuf + outlen, &tmp) != 1) {
        EVP_CIPHER_CTX_free(ectx);
        return SC_ERR_CRYPTO;
    }
    uint8_t tag[SC_TAG_SIZE];
    if (EVP_CIPHER_CTX_ctrl(ectx, EVP_CTRL_AEAD_GET_TAG, SC_TAG_SIZE, tag) != 1) {
        EVP_CIPHER_CTX_free(ectx);
        return SC_ERR_CRYPTO;
    }
    memcpy(ciphertext, nonce, SC_NONCE_SIZE);
    memcpy(ciphertext + SC_NONCE_SIZE, outbuf, total_plaintext_len);
    memcpy(ciphertext + SC_NONCE_SIZE + total_plaintext_len, tag, SC_TAG_SIZE);
    *ciphertext_len = SC_NONCE_SIZE + total_plaintext_len + SC_TAG_SIZE;
    ctx->tx_counter++;
    EVP_CIPHER_CTX_free(ectx);
    return SC_OK;
}

sc_status_t sc_decrypt(sc_context_t *ctx, const uint8_t *ciphertext, size_t ciphertext_len, uint8_t *plaintext, size_t *plaintext_len) {
    if (!ctx || !ciphertext || !plaintext || !plaintext_len) {
        return SC_ERR_INVALID_ARG;
    }
    if (!ctx->session_ready) {
        return SC_ERR_NOT_INITIALIZED;
    }
    if (ciphertext_len < SC_NONCE_SIZE + SC_TAG_SIZE + SC_CRC32_SIZE) {
        return SC_ERR_INVALID_ARG;
    }
    uint8_t nonce[SC_NONCE_SIZE];
    memcpy(nonce, ciphertext, SC_NONCE_SIZE);
    const uint8_t *encrypted_data = ciphertext + SC_NONCE_SIZE;
    size_t encrypted_len = ciphertext_len - SC_NONCE_SIZE;
    size_t total_plaintext_len = encrypted_len - SC_TAG_SIZE;
    uint8_t plaintext_with_crc[total_plaintext_len];
    EVP_CIPHER_CTX *dctx = EVP_CIPHER_CTX_new();
    if (!dctx) return SC_ERR_CRYPTO;
    if (EVP_DecryptInit_ex(dctx, EVP_aes_128_ccm(), NULL, NULL, NULL) != 1) {
        EVP_CIPHER_CTX_free(dctx);
        return SC_ERR_CRYPTO;
    }
    if (EVP_CIPHER_CTX_ctrl(dctx, EVP_CTRL_AEAD_SET_IVLEN, SC_NONCE_SIZE, NULL) != 1) {
        EVP_CIPHER_CTX_free(dctx);
        return SC_ERR_CRYPTO;
    }
    if (EVP_CIPHER_CTX_ctrl(dctx, EVP_CTRL_AEAD_SET_TAG, SC_TAG_SIZE, (void *)(encrypted_data + total_plaintext_len)) != 1) {
        EVP_CIPHER_CTX_free(dctx);
        return SC_ERR_CRYPTO;
    }
    if (EVP_DecryptInit_ex(dctx, NULL, NULL, ctx->session_key, nonce) != 1) {
        EVP_CIPHER_CTX_free(dctx);
        return SC_ERR_CRYPTO;
    }
    int outlen;
    if (EVP_DecryptUpdate(dctx, plaintext_with_crc, &outlen, encrypted_data, total_plaintext_len) != 1 ||
        outlen != (int)total_plaintext_len) {
        EVP_CIPHER_CTX_free(dctx);
        return SC_ERR_AUTH_FAILED;
    }
    int tmp;
    if (EVP_DecryptFinal_ex(dctx, plaintext_with_crc + outlen, &tmp) != 1) {
        EVP_CIPHER_CTX_free(dctx);
        return SC_ERR_AUTH_FAILED;
    }
    EVP_CIPHER_CTX_free(dctx);
    size_t data_len = total_plaintext_len - SC_CRC32_SIZE;
    uint32_t expected_crc = crc32_calc(plaintext_with_crc, data_len);
    uint32_t received_crc = (plaintext_with_crc[data_len] << 0) |
                           (plaintext_with_crc[data_len + 1] << 8) |
                           (plaintext_with_crc[data_len + 2] << 16) |
                           (plaintext_with_crc[data_len + 3] << 24);
    if (expected_crc != received_crc) {
        return SC_ERR_CRC_FAILED;
    }
    memcpy(plaintext, plaintext_with_crc, data_len);
    *plaintext_len = data_len;
    ctx->rx_counter++;
    return SC_OK;
}

sc_status_t sc_compute_public_key_from_private(const uint8_t *private_key, uint8_t *public_key) {
    if (!private_key || !public_key) {
        return SC_ERR_INVALID_ARG;
    }
    EC_GROUP *group = EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1);
    if (!group) return SC_ERR_CRYPTO;
    BIGNUM *priv = BN_bin2bn(private_key, SC_PRIVKEY_SIZE, NULL);
    if (!priv) {
        EC_GROUP_free(group);
        return SC_ERR_CRYPTO;
    }
    EC_POINT *pub_point = EC_POINT_new(group);
    if (!pub_point) {
        BN_free(priv);
        EC_GROUP_free(group);
        return SC_ERR_CRYPTO;
    }
    if (EC_POINT_mul(group, pub_point, priv, NULL, NULL, NULL) != 1) {
        EC_POINT_free(pub_point);
        BN_free(priv);
        EC_GROUP_free(group);
        return SC_ERR_CRYPTO;
    }
    uint8_t pub_buf[65];
    if (EC_POINT_point2oct(group, pub_point, POINT_CONVERSION_UNCOMPRESSED, pub_buf, 65, NULL) != 65) {
        EC_POINT_free(pub_point);
        BN_free(priv);
        EC_GROUP_free(group);
        return SC_ERR_CRYPTO;
    }
    memcpy(public_key, pub_buf + 1, SC_PUBKEY_SIZE);
    EC_POINT_free(pub_point);
    BN_free(priv);
    EC_GROUP_free(group);
    return SC_OK;
}

#else

// Original TinyCrypt implementations (unchanged logic)

static const struct uECC_Curve_t *curve = NULL;

static int sc_rng(uint8_t *dest, unsigned size)
{
    int fd = open("/dev/urandom", O_RDONLY);
    if (fd < 0) {
        return 0;
    }

    ssize_t ret = read(fd, dest, size);
    close(fd);
    if (ret != size) {
        return 0;
    }

    /* Mix in PID and microtime for additional entropy */
    pid_t pid = getpid();
    struct timeval tv;
    gettimeofday(&tv, NULL);

    for (unsigned i = 0; i < size; i++) {
        dest[i] ^= ((pid >> (i % (sizeof(pid) * 8))) & 0xFF);
        dest[i] ^= ((tv.tv_sec >> (i % (sizeof(tv.tv_sec) * 8))) & 0xFF);
        dest[i] ^= ((tv.tv_usec >> (i % (sizeof(tv.tv_usec) * 8))) & 0xFF);
    }

    return 1;
}

static int sc_validate_key(const uint8_t *public_key)
{
    if (!curve) {
        curve = uECC_secp256r1();
    }
    int result = uECC_valid_public_key(public_key, curve);
    DEBUG_INFO(DEBUG_CATEGORY_CRYPTO, "sc_validate_key: uECC_valid_public_key returned %d", result);
    return result;
}

sc_status_t sc_generate_keypair(struct SC_MYKEYS *pk)
{
    if (!pk) {
        return SC_ERR_INVALID_ARG;
    }

    if (!curve) {
        curve = uECC_secp256r1();
    }

    /* Set custom RNG function */
    uECC_set_rng(sc_rng);

    /* Try to generate valid key pair (max 10 attempts) */
    for (int attempt = 0; attempt < 10; attempt++) {
        if (!uECC_make_key(pk->public_key, pk->private_key, curve)) {
            continue;
        }
        /* Validate generated public key immediately */
        if (sc_validate_key(pk->public_key) == 0) {
            DEBUG_INFO(DEBUG_CATEGORY_CRYPTO, "sc_generate_keypair: generated valid keypair on attempt %d", attempt + 1);
            return SC_OK;
        }
        DEBUG_WARN(DEBUG_CATEGORY_CRYPTO, "sc_generate_keypair: generated invalid key on attempt %d, retrying...", attempt + 1);
    }
    
    DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_generate_keypair: failed to generate valid keypair after 10 attempts");
    return SC_ERR_CRYPTO;
}

sc_status_t sc_init_local_keys(struct SC_MYKEYS *mykeys, const char *public_key, const char *private_key) {
    if (!mykeys || !public_key || !private_key) {
        DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_init_local_keys: invalid arguments");
        return SC_ERR_INVALID_ARG;
    }

    if (!curve) {
        curve = uECC_secp256r1();
    }

    DEBUG_INFO(DEBUG_CATEGORY_CRYPTO, "sc_init_local_keys: public_key len=%zu, private_key len=%zu", 
               strlen(public_key), strlen(private_key));

    /* Convert hex to binary first */
    if (hex_to_binary(public_key, mykeys->public_key, SC_PUBKEY_SIZE)) {
        DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_init_local_keys: failed to convert public key from hex");
        return SC_ERR_INVALID_ARG;
    }
    if (hex_to_binary(private_key, mykeys->private_key, SC_PRIVKEY_SIZE)) {
        DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_init_local_keys: failed to convert private key from hex");
        return SC_ERR_INVALID_ARG;
    }

    /* Validate the converted binary public key */
    if (sc_validate_key(mykeys->public_key) != 0) {
        DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_init_local_keys: public key validation failed");
        return SC_ERR_INVALID_ARG;
    }

    DEBUG_INFO(DEBUG_CATEGORY_CRYPTO, "sc_init_local_keys: keys initialized successfully");
    return SC_OK;
}

sc_status_t sc_set_peer_public_key(sc_context_t *ctx, const char *peer_public_key_h, int mode) {
    uint8_t shared_secret[SC_SHARED_SECRET_SIZE];
    uint8_t peer_public_key[SC_PUBKEY_SIZE];

    if (mode) {
      if (hex_to_binary(peer_public_key_h, peer_public_key, SC_PUBKEY_SIZE)) {
          DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_set_peer_public_key: invalid hex key format");
          return SC_ERR_INVALID_ARG;
          }
      }
    else memcpy(peer_public_key, peer_public_key_h, SC_PUBKEY_SIZE);

    if (!ctx) {
        DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_set_peer_public_key: invalid ctx");
        return SC_ERR_INVALID_ARG;
    }

    if (!ctx->initialized) {
        DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_set_peer_public_key: ctx not initialized");
        return SC_ERR_NOT_INITIALIZED;
    }

    if (!curve) {
        curve = uECC_secp256r1();
    }

    /* Validate peer public key */
    if (sc_validate_key(peer_public_key) != 0) {
        DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_set_peer_public_key: invalid key");
        return SC_ERR_INVALID_ARG;
    }

    /* Compute shared secret using ECDH */
    if (!ctx->pk) {
        DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_set_peer_public_key: no private key");
        return SC_ERR_NOT_INITIALIZED;
    }
    if (!uECC_shared_secret(peer_public_key, ctx->pk->private_key,
                            shared_secret, curve)) {
        DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_set_peer_public_key: shared secret error");
        return SC_ERR_CRYPTO;
    }

    /* Derive session key from shared secret (simple copy for demo) */
    memcpy(ctx->session_key, shared_secret, SC_SESSION_KEY_SIZE);

    /* Store peer public key */
    memcpy(ctx->peer_public_key, peer_public_key, SC_PUBKEY_SIZE);
    ctx->peer_key_set = 1;

    ctx->session_ready = 1;

    return SC_OK;
}

static void sc_build_nonce(uint64_t counter, uint8_t *nonce_out)
{
    struct tc_sha256_state_struct sha_ctx;
    uint8_t hash[32];
    struct timeval tv;
    uint8_t data[8 + 8 + 8];

    if (!sc_urandom_initialized) {
        sc_init_random_seed();
    }

    gettimeofday(&tv, NULL);

    memcpy(data, sc_urandom_seed, 8);
    data[8] = (counter >> 0) & 0xFF;
    data[9] = (counter >> 8) & 0xFF;
    data[10] = (counter >> 16) & 0xFF;
    data[11] = (counter >> 24) & 0xFF;
    data[12] = (counter >> 32) & 0xFF;
    data[13] = (counter >> 40) & 0xFF;
    data[14] = (counter >> 48) & 0xFF;
    data[15] = (counter >> 56) & 0xFF;
    data[16] = (tv.tv_sec >> 0) & 0xFF;
    data[17] = (tv.tv_sec >> 8) & 0xFF;
    data[18] = (tv.tv_sec >> 16) & 0xFF;
    data[19] = (tv.tv_sec >> 24) & 0xFF;
    data[20] = (tv.tv_usec >> 0) & 0xFF;
    data[21] = (tv.tv_usec >> 8) & 0xFF;
    data[22] = (tv.tv_usec >> 16) & 0xFF;
    data[23] = (tv.tv_usec >> 24) & 0xFF;

    tc_sha256_init(&sha_ctx);
    tc_sha256_update(&sha_ctx, data, 24);
    tc_sha256_final(hash, &sha_ctx);

    memcpy(nonce_out, hash, SC_NONCE_SIZE);
}

sc_status_t sc_encrypt(sc_context_t *ctx, const uint8_t *plaintext, size_t plaintext_len, uint8_t *ciphertext, size_t *ciphertext_len) {
    uint8_t nonce[SC_NONCE_SIZE];
    uint8_t plaintext_with_crc[plaintext_len + SC_CRC32_SIZE];
    size_t total_plaintext_len = plaintext_len + SC_CRC32_SIZE;
    uint8_t combined_output[total_plaintext_len + SC_TAG_SIZE];
    struct tc_aes_key_sched_struct sched;
    struct tc_ccm_mode_struct ccm_state;

    if (!ctx || !plaintext || !ciphertext || !ciphertext_len) {
        return SC_ERR_INVALID_ARG;
    }

    if (!ctx->session_ready) {
        return SC_ERR_NOT_INITIALIZED;
    }

    if (plaintext_len == 0) {
        return SC_ERR_INVALID_ARG;
    }

    /* Добавляем CRC32 к данным */
    memcpy(plaintext_with_crc, plaintext, plaintext_len);
    uint32_t crc = crc32_calc(plaintext, plaintext_len);
    plaintext_with_crc[plaintext_len] = (crc >> 0) & 0xFF;
    plaintext_with_crc[plaintext_len + 1] = (crc >> 8) & 0xFF;
    plaintext_with_crc[plaintext_len + 2] = (crc >> 16) & 0xFF;
    plaintext_with_crc[plaintext_len + 3] = (crc >> 24) & 0xFF;

    /* Генерируем nonce с таймером */
    sc_build_nonce(ctx->tx_counter, nonce);

    /* Initialize AES key schedule */
    if (tc_aes128_set_encrypt_key(&sched, ctx->session_key) != TC_CRYPTO_SUCCESS) {
        return SC_ERR_CRYPTO;
    }

    /* Configure CCM mode */
    if (tc_ccm_config(&ccm_state, &sched, nonce, SC_NONCE_SIZE, SC_TAG_SIZE) != TC_CRYPTO_SUCCESS) {
        return SC_ERR_CRYPTO;
    }

    /* Encrypt and generate tag */
    if (tc_ccm_generation_encryption(combined_output, sizeof(combined_output),
                                     NULL, 0, /* no associated data */
                                     plaintext_with_crc, total_plaintext_len,
                                     &ccm_state) != TC_CRYPTO_SUCCESS) {
        return SC_ERR_CRYPTO;
    }

    /* Copy nonce + ciphertext + tag to output buffer */
    memcpy(ciphertext, nonce, SC_NONCE_SIZE);
    memcpy(ciphertext + SC_NONCE_SIZE, combined_output, total_plaintext_len + SC_TAG_SIZE);
    *ciphertext_len = SC_NONCE_SIZE + total_plaintext_len + SC_TAG_SIZE;

    ctx->tx_counter++;

    return SC_OK;
}

sc_status_t sc_decrypt(sc_context_t *ctx,
                       const uint8_t *ciphertext,
                       size_t ciphertext_len,
                       uint8_t *plaintext,
                       size_t *plaintext_len)
{
    uint8_t nonce[SC_NONCE_SIZE];
    struct tc_aes_key_sched_struct sched;
    struct tc_ccm_mode_struct ccm_state;
    size_t total_plaintext_len = ciphertext_len - SC_NONCE_SIZE - SC_TAG_SIZE;
    uint8_t plaintext_with_crc[total_plaintext_len];

    if (!ctx || !ciphertext || !plaintext || !plaintext_len) {
        return SC_ERR_INVALID_ARG;
    }

    if (!ctx->session_ready) {
        return SC_ERR_NOT_INITIALIZED;
    }

    if (ciphertext_len < SC_NONCE_SIZE + SC_TAG_SIZE + SC_CRC32_SIZE) {
        return SC_ERR_INVALID_ARG;
    }

    /* Извлекаем nonce из начала ciphertext */
    memcpy(nonce, ciphertext, SC_NONCE_SIZE);

    /* Ciphertext для расшифровки начинается после nonce */
    const uint8_t *encrypted_data = ciphertext + SC_NONCE_SIZE;
    size_t encrypted_len = ciphertext_len - SC_NONCE_SIZE;

    /* Initialize AES key schedule */
    if (tc_aes128_set_encrypt_key(&sched, ctx->session_key) != TC_CRYPTO_SUCCESS) {
        return SC_ERR_CRYPTO;
    }

    /* Configure CCM mode с извлечённым nonce */
    if (tc_ccm_config(&ccm_state, &sched, nonce, SC_NONCE_SIZE, SC_TAG_SIZE) != TC_CRYPTO_SUCCESS) {
        return SC_ERR_CRYPTO;
    }

    /* Decrypt and verify tag */
    if (tc_ccm_decryption_verification(plaintext_with_crc, total_plaintext_len,
                                       NULL, 0, /* no associated data */
                                       encrypted_data, encrypted_len,
                                       &ccm_state) != TC_CRYPTO_SUCCESS) {
        return SC_ERR_AUTH_FAILED;
    }

    /* Проверяем CRC32 */
    size_t data_len = total_plaintext_len - SC_CRC32_SIZE;
    uint32_t expected_crc = crc32_calc(plaintext_with_crc, data_len);
    uint32_t received_crc = (plaintext_with_crc[data_len] << 0) |
                           (plaintext_with_crc[data_len + 1] << 8) |
                           (plaintext_with_crc[data_len + 2] << 16) |
                           (plaintext_with_crc[data_len + 3] << 24);
    
    if (expected_crc != received_crc) {
        return SC_ERR_CRC_FAILED;
    }

    /* Копируем данные без CRC32 */
    memcpy(plaintext, plaintext_with_crc, data_len);
    *plaintext_len = data_len;

    ctx->rx_counter++;

    return SC_OK;
}

sc_status_t sc_compute_public_key_from_private(const uint8_t *private_key, uint8_t *public_key) {
    if (!private_key || !public_key) {
        return SC_ERR_INVALID_ARG;
    }

    if (!curve) {
        curve = uECC_secp256r1();
    }

    if (!uECC_compute_public_key(private_key, public_key, curve)) {
        return SC_ERR_CRYPTO;
    }
    return SC_OK;
}

#endif

sc_status_t sc_sha_transcode(const uint8_t *key, size_t key_len, uint8_t *data, size_t data_len) {
    if (!key || !data || key_len == 0 || data_len == 0) {
        return SC_ERR_INVALID_ARG;
    }
    
    uint8_t sha_hash[SC_SHA256_BLOCK_SIZE];
    SC_SHA256_CTX ctx;
    
    sc_sha256_init(&ctx);
    sc_sha256_update(&ctx, key, key_len);
    sc_sha256_final(&ctx, sha_hash);
    
    for (size_t i = 0; i < data_len; i++) {
        data[i] ^= sha_hash[i % SC_SHA256_BLOCK_SIZE];
    }
    
    return SC_OK;
}