symmetric encryption added

delivery1/lib/symmetric_encryption.py

@@ -0,0 +1,55 @@
+import os
+from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC
+from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
+from cryptography.hazmat.backends import default_backend
+
+# Function to derive a 256-bit key from a password and salt
+def derive_key(passwd, salt):
+	kdf = PBKDF2HMAC(
+		algorithm=hashes.SHA256(),
+		length=32,
+		salt=salt,
+		iterations=10000,
+		backend=default_backend()
+	)
+	key = kdf.derive(passwd.encode())
+	return key.hex()
+
+
+# Function to encrypt a file using a password
+def encrypt_file(passwd, input_file, output_file):
+	salt = os.urandom(16)
+	key = derive_key(passwd, salt)
+	iv = os.urandom(16)
+	cipher = Cipher(algorithms.AES(key), modes.CFB(iv), backend=default_backend())
+	encryptor = cipher.encryptor()
+
+	with open(input_file, 'rb') as f:
+		plaintext = f.read()
+
+	ciphertext = encryptor.update(plaintext) + encryptor.finalize()
+
+	with open(output_file, 'wb') as f:
+		f.write(salt + iv + ciphertext)
+
+
+# Function to decrypt a file using a password
+def decrypt_file(passwd, input_file, output_file=None):
+	with open(input_file, 'rb') as f:
+		encrypted_data = f.read()
+
+	salt = encrypted_data[:16]
+	iv = encrypted_data[16:32]
+	ciphertext = encrypted_data[32:]
+	key = derive_key(passwd, salt)
+	cipher = Cipher(algorithms.AES(key), modes.CFB(iv), backend=default_backend())
+	decryptor = cipher.decryptor()
+
+	plaintext = decryptor.update(ciphertext) + decryptor.finalize()
+
+	if output_file is None:
+		return plaintext
+	else:
+		with open(output_file, 'wb') as f:
+			f.write(plaintext)