# 🔐 DVT_RFSA — Hybrid Encryption Library

> A robust **hybrid encryption** library combining **RSA + X25519 + AES-256-GCM** for text & file encryption, with optional password protection.

**DVT_RFSA** is a Python cryptography library that implements hybrid encryption schemes:
- **AES-256-GCM** for data encryption
- **RSA-2048** and **X25519 (ECDH)** for key exchange
- Optional **password-derived key** protection (PBKDF2/HKDF)
- Support for encrypting text, files, and binary data
- Includes security metadata (algorithm, key info) for interchange

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## ✨ Encryption Schemes

| Scheme | Description |
|--------|-------------|
| **AES + RSA** | Hybrid: AES-256-GCM session key wrapped with RSA-2048 public key |
| **AES + X25519** | Hybrid: AES-256-GCM session key via X25519 ECDH key exchange |
| **AES + RSA + Password** | Above + password-derived key layered encryption |
| **Pure AES** | Direct AES-256-GCM with generated/password-derived key |

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## 🔌 Core Functions

### Hashing & Key Tools
- `compute_data_hash(data, algorithm='sha256')` / `verify_data_hash(...)`
- `generate_aes_key()` / `derive_key_from_password(...)`
- `is_password_strong(...)` / `generate_strong_password(...)`

### Key Generation
- `generate_rsa_key()` — RSA-2048 keypair
- `generate_x25519_keys()` — X25519 keypair
- `load_x25519_private_key(...)` / `load_x25519_public_key(...)`

### Data Encryption (text / bytes)
- `aes_encrypt` / `aes_decrypt`
- `encrypt_aes_rsa` / `decrypt_aes_rsa`
- `encrypt_aes_x25519` / `decrypt_aes_x25519`
- `encrypt_aes_rsa_with_password` / `decrypt_aes_rsa_with_password`

### File Encryption
- `encrypt_file_aes_rsa` / `decrypt_file_aes_rsa`
- `encrypt_file_aes_rsa_with_password` / `decrypt_file_aes_rsa_with_password`
- `encrypt_file_aes_x25519` / `decrypt_file_aes_x25519`

### Text Convenience
- `encrypt_text_aes_rsa` / `decrypt_text_aes_rsa`
- `encrypt_text_aes_rsa_with_password` / `decrypt_text_aes_rsa_with_password`
- `encrypt_text_aes_x25519` / `decrypt_text_aes_x25519`

### Metadata
- `add_security_info(...)` / `remove_security_info(...)`

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## 🚀 Quick Start

### Prerequisites

```bash
pip install cryptography
```

### Example: Encrypt/Decrypt a File (AES + RSA)

```python
import DVT_RFSA as rf

# Generate RSA keys
keys = rf.generate_rsa_key()

# Encrypt a file
rf.encrypt_file_aes_rsa("secret.txt", "secret.txt.enc", keys["public"])

# Decrypt the file
rf.decrypt_file_aes_rsa("secret.txt.enc", "secret_decrypted.txt", keys["private"])
```

### Example: Text Encryption with Password

```python
import DVT_RFSA as rf

password = rf.generate_strong_password()
enc = rf.encrypt_text_aes_rsa_with_password("Hello, world!", password)
dec = rf.decrypt_text_aes_rsa_with_password(enc, password)
print(dec)  # Hello, world!
```

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## 🛡️ Features

- **Authenticated encryption** (AES-256-GCM) — detects tampering
- **Hybrid key exchange** — RSA & X25519 (ECDH)
- **Password protection** — key derivation & layered encryption
- **File & text support** — encrypt whole files or strings
- **Portable output** — encrypted data carries security metadata
- **Debug logging** — optional `crypto_log` with timestamp

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## 📁 Project Structure

```
dvt-rfsa/
├── DVT_RFSA.py   # Hybrid encryption library
└── README.md     # This document
```

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## 📄 License

This project is licensed under the **MIT License**. See [LICENSE](LICENSE) for details.

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## ⚠️ Security Note

> This library is for **learning and reference**. For production, ensure secure key storage, use strong passwords, and review the cryptographic implementation carefully.