| |
| import base64 |
| import hashlib |
| from cryptography.hazmat.primitives.ciphers.aead import AESGCM |
|
|
| def derive_key(key_str: str) -> bytes: |
| """Derive 32-byte key from a passphrase using SHA-256.""" |
| if not isinstance(key_str, str) or not key_str: |
| raise ValueError("key_str must be a non-empty string") |
| return hashlib.sha256(key_str.encode("utf-8")).digest() |
|
|
| def encrypt_text(plaintext: str, key: bytes, iv: bytes) -> dict: |
| """Encrypt plaintext with AES-256-GCM. Returns dict with iv, ciphertext, tag (base64).""" |
| if plaintext is None: |
| plaintext = "" |
| aes = AESGCM(key) |
| ct = aes.encrypt(iv, plaintext.encode("utf-8"), None) |
| ciphertext, tag = ct[:-16], ct[-16:] |
| return { |
| "iv": base64.b64encode(iv).decode("ascii"), |
| "ciphertext": base64.b64encode(ciphertext).decode("ascii"), |
| "tag": base64.b64encode(tag).decode("ascii"), |
| } |
|
|
| def decrypt_text(enc: dict, key: bytes) -> str: |
| """Decrypt dict with iv/ciphertext/tag (base64).""" |
| iv = base64.b64decode(enc["iv"]) |
| ciphertext = base64.b64decode(enc["ciphertext"]) |
| tag = base64.b64decode(enc["tag"]) |
| aes = AESGCM(key) |
| plaintext = aes.decrypt(iv, ciphertext + tag, None) |
| return plaintext.decode("utf-8") |
|
|
