Merge pull request #418 from reaperhulk/move-contexts
Move ciphercontext/aeadciphercontext to bottom of symmetric encryption
diff --git a/docs/hazmat/primitives/symmetric-encryption.rst b/docs/hazmat/primitives/symmetric-encryption.rst
index c1f7bb6..2233d52 100644
--- a/docs/hazmat/primitives/symmetric-encryption.rst
+++ b/docs/hazmat/primitives/symmetric-encryption.rst
@@ -291,8 +291,6 @@
Cipher, algorithms, modes
)
- from cryptography.hazmat.primitives.padding import PKCS7
-
def encrypt(key, plaintext, associated_data):
# Generate a random 96-bit IV.
iv = os.urandom(12)
@@ -305,17 +303,13 @@
backend=default_backend()
).encryptor()
- # We have to pad our plaintext because it may not be a
- # multiple of the block size.
- padder = PKCS7(algorithms.AES.block_size).padder()
- padded_plaintext = padder.update(plaintext) + padder.finalize()
-
# associated_data will be authenticated but not encrypted,
# it must also be passed in on decryption.
encryptor.authenticate_additional_data(associated_data)
# Encrypt the plaintext and get the associated ciphertext.
- ciphertext = encryptor.update(padded_plaintext) + encryptor.finalize()
+ # GCM does not require padding.
+ ciphertext = encryptor.update(plaintext) + encryptor.finalize()
return (iv, ciphertext, encryptor.tag)
@@ -328,17 +322,13 @@
backend=default_backend()
).decryptor()
- # We will need to unpad the plaintext.
- unpadder = PKCS7(algorithms.AES.block_size).unpadder()
-
# We put associated_data back in or the tag will fail to verify
# when we finalize the decryptor.
decryptor.authenticate_additional_data(associated_data)
- # Decryption gets us the authenticated padded plaintext.
- padded_plaintext = decryptor.update(ciphertext) + decryptor.finalize()
-
- return unpadder.update(padded_plaintext) + unpadder.finalize()
+ # Decryption gets us the authenticated plaintext.
+ # If the tag does not match an InvalidTag exception will be raised.
+ return decryptor.update(ciphertext) + decryptor.finalize()
iv, ciphertext, tag = encrypt(
key,