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691fc0b | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 | #!/usr/bin/env python3
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")
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