AES-GCM in python

TPs/TP03/py/pbenc_aes_gcm_hmac.py

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+import os
+from cryptography.hazmat.primitives.ciphers.aead import AESGCM
+import argparse
+
+def setup(key_file):
+    key = AESGCM.generate_key(bit_length=128)
+    with open(key_file, "wb") as f:
+        f.write(key)
+
+
+def encrypt(input_file, key_file):
+    with open(input_file, "rb") as f:
+        plaintext = f.read()
+
+    with open(key_file, "rb") as f:
+        key = f.read()
+
+    aad = b"authenticated but unencrypted data"
+    aesgcm = AESGCM(key)
+    nonce = os.urandom(12)
+
+    ct = aesgcm.encrypt(nonce, plaintext, aad)
+
+    with open(f"{input_file}.enc", "wb") as f:
+        f.write(nonce)
+        f.write(ct)
+
+
+def decrypt(input_file, key_file):
+    with open(input_file, "rb") as f:
+        nonce = f.read(12)
+        ct = f.read()
+
+    with open(key_file, "rb") as f:
+        key = f.read()
+
+    aad = b"authenticated but unencrypted data"
+    aesgcm = AESGCM(key)
+    pt = aesgcm.decrypt(nonce, ct, aad)
+
+    with open(f"{input_file}.dec", "wb") as f:
+        f.write(pt)
+
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Program to perform operations using AES-GCM cipher on files",
+    )
+
+    subparsers = parser.add_subparsers(dest="operation", help="Operation to perform")
+
+    # Encrypt subcommand
+    enc_parser = subparsers.add_parser("enc", help="Encrypt a file")
+    enc_parser.add_argument("fich", help="File to be encrypted")
+    enc_parser.add_argument("password", help="Pass-phrase to derive the key")
+
+    # Decrypt subcommand
+    dec_parser = subparsers.add_parser("dec", help="Decrypt a file")
+    dec_parser.add_argument("fich", help="File to be decrypted")
+    dec_parser.add_argument("password", help="Pass-phrase to derive the key")
+
+    args = parser.parse_args()
+    match args.operation:
+        case "enc":
+            input_file = args.fich
+            password = args.password
+            encrypt(input_file,password)
+        case "dec":
+            input_file = args.fich
+            password = args.password
+            decrypt(input_file,password)
+
+if __name__ == "__main__":
+    main()
+