crypto.h

#ifndef CRYPTO_H
#define CRYPTO_H

#include <stddef.h>
#include <stdint.h>

#define SALT_LEN          16
#define NONCE_LEN         12
#define KEY_LEN           32
#define GCM_TAG_LEN       16
#define HEADER_SIZE       48   /* 16 + 12 + 4 + 8 + 8 */
#define DEFAULT_CHUNK_SIZE (1024 * 1024)

/*
 * Encrypt src → dst using AES-256-GCM / Argon2id.
 * File format: [salt:16][base_nonce:12][chunk_size:4 BE][file_size:8 BE][num_chunks:8 BE]
 *              followed by chunks, each: [ciphertext_len:4 BE][ciphertext+tag]
 */
int encrypt_file(const char *src, const char *dst,
                 const uint8_t *password, size_t pass_len, int chunk_size);

/*
 * Decrypt src → dst.
 * Wrong-password: silently produces a deterministic decoy output.
 */
int decrypt_file(const char *src, const char *dst,
                 const uint8_t *password, size_t pass_len);

#endif /* CRYPTO_H */