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Counter with CBC-MAC (CCM) mode.
CcmMode N) unhexlify) byte_stringbord _copy_bytes)is_writeable_buffer)strxor)
long_to_bytes)BLAKE2s)get_random_bytesc $ t dd| S )NEnum )type)enumss y/builddir/build/BUILD/imunify360-venv-2.6.2/opt/imunify360/venv/lib64/python3.11/site-packages/Crypto/Cipher/_mode_ccm.pyenumr 3 s E " "" ) NOT_STARTEDPROCESSING_AUTH_DATAPROCESSING_PLAINTEXTc p e Zd ZdZd Zd Zd Zd ZddZdd Z dd
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d Zd ZddZddZdS )r a Counter with CBC-MAC (CCM).
This is an Authenticated Encryption with Associated Data (`AEAD`_) mode.
It provides both confidentiality and authenticity.
The header of the message may be left in the clear, if needed, and it will
still be subject to authentication. The decryption step tells the receiver
if the message comes from a source that really knowns the secret key.
Additionally, decryption detects if any part of the message - including the
header - has been modified or corrupted.
This mode requires a nonce. The nonce shall never repeat for two
different messages encrypted with the same key, but it does not need
to be random.
Note that there is a trade-off between the size of the nonce and the
maximum size of a single message you can encrypt.
It is important to use a large nonce if the key is reused across several
messages and the nonce is chosen randomly.
It is acceptable to us a short nonce if the key is only used a few times or
if the nonce is taken from a counter.
The following table shows the trade-off when the nonce is chosen at
random. The column on the left shows how many messages it takes
for the keystream to repeat **on average**. In practice, you will want to
stop using the key way before that.
+--------------------+---------------+-------------------+
| Avg. # of messages | nonce | Max. message |
| before keystream | size | size |
| repeats | (bytes) | (bytes) |
+====================+===============+===================+
| 2^52 | 13 | 64K |
+--------------------+---------------+-------------------+
| 2^48 | 12 | 16M |
+--------------------+---------------+-------------------+
| 2^44 | 11 | 4G |
+--------------------+---------------+-------------------+
| 2^40 | 10 | 1T |
+--------------------+---------------+-------------------+
| 2^36 | 9 | 64P |
+--------------------+---------------+-------------------+
| 2^32 | 8 | 16E |
+--------------------+---------------+-------------------+
This mode is only available for ciphers that operate on 128 bits blocks
(e.g. AES but not TDES).
See `NIST SP800-38C`_ or RFC3610_.
.. _`NIST SP800-38C`: http://csrc.nist.gov/publications/nistpubs/800-38C/SP800-38C.pdf
.. _RFC3610: https://tools.ietf.org/html/rfc3610
.. _AEAD: http://blog.cryptographyengineering.com/2012/05/how-to-choose-authenticated-encryption.html
:undocumented: __init__
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| | | j || S ) ab Encrypt data with the key set at initialization.
A cipher object is stateful: once you have encrypted a message
you cannot encrypt (or decrypt) another message using the same
object.
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not passed at initialization.
If ``msg_len`` was given, the data to encrypt can be broken
up in two or more pieces and `encrypt` can be called
multiple times.
That is, the statement:
>>> c.encrypt(a) + c.encrypt(b)
is equivalent to:
>>> c.encrypt(a+b)
This function does not add any padding to the plaintext.
:Parameters:
plaintext : bytes/bytearray/memoryview
The piece of data to encrypt.
It can be of any length.
:Keywords:
output : bytearray/memoryview
The location where the ciphertext must be written to.
If ``None``, the ciphertext is returned.
:Return:
If ``output`` is ``None``, the ciphertext as ``bytes``.
Otherwise, ``None``.
r( z@encrypt() can only be called after initialization or an update()r* Nc , g | ]}t | S r r8 .0xs r
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| j || }|| | n| | |S ) ad Decrypt data with the key set at initialization.
A cipher object is stateful: once you have decrypted a message
you cannot decrypt (or encrypt) another message with the same
object.
This method can be called only **once** if ``msg_len`` was
not passed at initialization.
If ``msg_len`` was given, the data to decrypt can be
broken up in two or more pieces and `decrypt` can be
called multiple times.
That is, the statement:
>>> c.decrypt(a) + c.decrypt(b)
is equivalent to:
>>> c.decrypt(a+b)
This function does not remove any padding from the plaintext.
:Parameters:
ciphertext : bytes/bytearray/memoryview
The piece of data to decrypt.
It can be of any length.
:Keywords:
output : bytearray/memoryview
The location where the plaintext must be written to.
If ``None``, the plaintext is returned.
:Return:
If ``output`` is ``None``, the plaintext as ``bytes``.
Otherwise, ``None``.
r) z@decrypt() can only be called after initialization or an update()r+ Nc , g | ]}t | S r rm rn s r rq z#CcmMode.decrypt.. rr r rs rt ru )r? rc r4 rT rB rU rw r3 rH r@ r7 r8 rA r= r< r ra r rF r( rX )rI
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& & ( ( ( ( =D L((F(CC > LL # # # # LL r c j d| j vrt d dg| _ | S )zCompute the *binary* MAC tag.
The caller invokes this function at the very end.
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} r c d d d | D S )zCompute the *printable* MAC tag.
This method is like `digest`.
:Return: the MAC, as a hexadecimal string.
c 2 g | ]}d t | z S )z%02x)r rn s r rq z%CcmMode.hexdigest.. s# @@@Qa(@@@r )rW r* r s r hexdigestzCcmMode.hexdigest s- ww@@$++--@@@AAAr c d d| j vrt d dg| _ | t d }t j d|| j }t j d|| }| | k rt d dS )a( Validate the *binary* MAC tag.
The caller invokes this function at the very end.
This method checks if the decrypted message is indeed valid
(that is, if the key is correct) and it has not been
tampered with while in transit.
:Parameters:
received_mac_tag : bytes/bytearray/memoryview
This is the *binary* MAC, as received from the sender.
:Raises ValueError:
if the MAC does not match. The message has been tampered with
or the key is incorrect.
r+ z3verify() cannot be called when encrypting a messager ) digest_bitsrK datazMAC check failedN) r? rc r~ r r r9 r6 r* r7 )rI received_mac_tagsecretmac1mac2s r r+ zCcmMode.verify s " 4: % % 9 : :
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This method is like `verify`.
:Parameters:
hex_mac_tag : string
This is the *printable* MAC, as received from the sender.
:Raises ValueError:
if the MAC does not match. The message has been tampered with
or the key is incorrect.
N)r+ r )rI hex_mac_tags r hexverifyzCcmMode.hexverify s$
Ik**+++++r c X | || | fS )a\ Perform encrypt() and digest() in one step.
:Parameters:
plaintext : bytes/bytearray/memoryview
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:Keywords:
output : bytearray/memoryview
The location where the ciphertext must be written to.
If ``None``, the ciphertext is returned.
:Return:
a tuple with two items:
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- the MAC tag, as ``bytes``
The first item becomes ``None`` when the ``output`` parameter
specified a location for the result.
ru )r( r* rx s r encrypt_and_digestzCcmMode.encrypt_and_digest+ s' ( ||If|55t{{}}DDr c ^ | || }| | |S )a Perform decrypt() and verify() in one step.
:Parameters:
ciphertext : bytes/bytearray/memoryview
The piece of data to decrypt.
received_mac_tag : bytes/bytearray/memoryview
This is the *binary* MAC, as received from the sender.
:Keywords:
output : bytearray/memoryview
The location where the plaintext must be written to.
If ``None``, the plaintext is returned.
:Return: the plaintext as ``bytes`` or ``None`` when the ``output``
parameter specified a location for the result.
:Raises ValueError:
if the MAC does not match. The message has been tampered with
or the key is incorrect.
ru )r) r+ )rI r| r rv ry s r decrypt_and_verifyzCcmMode.decrypt_and_verifyA s2 & LLFL;; $%%%r )r )N)__name__
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| }t | |||||| S ) aN Create a new block cipher, configured in CCM mode.
:Parameters:
factory : module
A symmetric cipher module from `Crypto.Cipher` (like
`Crypto.Cipher.AES`).
:Keywords:
key : bytes/bytearray/memoryview
The secret key to use in the symmetric cipher.
nonce : bytes/bytearray/memoryview
A value that must never be reused for any other encryption.
Its length must be in the range ``[7..13]``.
11 or 12 bytes are reasonable values in general. Bear in
mind that with CCM there is a trade-off between nonce length and
maximum message size.
If not specified, a 11 byte long random string is used.
mac_len : integer
Length of the MAC, in bytes. It must be even and in
the range ``[4..16]``. The default is 16.
msg_len : integer
Length of the message to (de)cipher.
If not specified, ``encrypt`` or ``decrypt`` may only be called once.
assoc_len : integer
Length of the associated data.
If not specified, all data is internally buffered.
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