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File Content: Counter.pyo

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���Z�d�S(���s���Fast counter functions for CTR cipher modes.

CTR is a chaining mode for symmetric block encryption or decryption.
Messages are divideded into blocks, and the cipher operation takes
place on each block using the secret key and a unique *counter block*.

The most straightforward way to fulfil the uniqueness property is
to start with an initial, random *counter block* value, and increment it as
the next block is processed.

The block ciphers from `Crypto.Cipher` (when configured in *MODE_CTR* mode)
invoke a callable object (the *counter* parameter) to get the next *counter block*.
Unfortunately, the Python calling protocol leads to major performance degradations.

The counter functions instantiated by this module will be invoked directly
by the ciphers in `Crypto.Cipher`. The fact that the Python layer is bypassed
lead to more efficient (and faster) execution of CTR cipher modes.

An example of usage is the following:

>>> from Crypto.Cipher import AES
    >>> from Crypto.Util import Counter
    >>>
    >>> pt = b'�'*1000000
    >>> ctr = Counter.new(128)
    >>> cipher = AES.new(b'�'*16, AES.MODE_CTR, counter=ctr)
    >>> ct = cipher.encrypt(pt)

:undocumented: __package__
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�S(���sc��Create a stateful counter block function suitable for CTR encryption modes.

Each call to the function returns the next counter block.
    Each counter block is made up by three parts::
 
      prefix || counter value || postfix

The counter value is incremented by one at each call.

:Parameters:
      nbits : integer
        Length of the desired counter, in bits. It must be a multiple of 8.
      prefix : byte string
        The constant prefix of the counter block. By default, no prefix is
        used.
      suffix : byte string
        The constant postfix of the counter block. By default, no suffix is
        used.
      initial_value : integer
        The initial value of the counter. Default value is 1.
      little_endian : boolean
        If True, the counter number will be encoded in little endian format.
        If False (default), in big endian format.
      allow_wraparound : boolean
        If True, the function will raise an *OverflowError* exception as soon
        as the counter wraps around. If False (default), the counter will
        simply restart from zero.
      disable_shortcut : boolean
        If True, do not make ciphers from `Crypto.Cipher` bypass the Python
        layer when invoking the counter block function.
        If False (default), bypass the Python layer.
    :Returns:
      The counter block function.
    i���i����s%���nbits must be a multiple of 8; got %di���s���nbits too smalli����s���nbits too larget���allow_wraparoundt���disable_shortcutN(���t���divmodt
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���little_endianR���R���t���nbytest	���remaindert���initval(����(����sF���/opt/alt/python27/lib64/python2.7/site-packages/Crypto/Util/Counter.pyt���new?���s����%+c���������C���s����g��}�t��|����}��xX�t�|���D]J�}�|�rE�|�j�t�|��d�@����n�|�j�d�t�|��d�@����|��d�L}��q�Wt�d���j�|���S(���Ni����i����i���R���(���t���longt���ranget���appendt���bchrt���insertt���bt���join(���t���nR���R���t���retvalt���i(����(����sF���/opt/alt/python27/lib64/python2.7/site-packages/Crypto/Util/Counter.pyR���t���s����(���t���__doc__t���syst���version_infot���Crypto.Util.py21compatt���Crypto.Util.py3compatt���Crypto.UtilR���t���structR���t���FalseR���R���(����(����(����sF���/opt/alt/python27/lib64/python2.7/site-packages/Crypto/Util/Counter.pyt���<module>5���s���&
*5

Name	Size	Permission
Counter.py	5157 bytes	0644
Counter.pyc	4249 bytes	0644
Counter.pyo	4249 bytes	0644
RFC1751.py	21186 bytes	0644
RFC1751.pyc	29332 bytes	0644
RFC1751.pyo	29332 bytes	0644
__init__.py	1507 bytes	0644
__init__.pyc	731 bytes	0644
__init__.pyo	731 bytes	0644
_counter.so	16600 bytes	0755
_number_new.py	4051 bytes	0644
_number_new.pyc	3617 bytes	0644
_number_new.pyo	3496 bytes	0644
asn1.py	12727 bytes	0644
asn1.pyc	14160 bytes	0644
asn1.pyo	14160 bytes	0644
number.py	95488 bytes	0644
number.pyc	113772 bytes	0644
number.pyo	113722 bytes	0644
py21compat.py	2779 bytes	0644
py21compat.pyc	1465 bytes	0644
py21compat.pyo	1465 bytes	0644
py3compat.py	3912 bytes	0644
py3compat.pyc	4261 bytes	0644
py3compat.pyo	4261 bytes	0644
randpool.py	2768 bytes	0644
randpool.pyc	3404 bytes	0644
randpool.pyo	3404 bytes	0644
strxor.so	11520 bytes	0755
winrandom.py	1196 bytes	0644
winrandom.pyc	253 bytes	0644
winrandom.pyo	253 bytes	0644