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Filename : SHA.py
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# -*- coding: utf-8 -*-
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"""SHA-1 cryptographic hash algorithm.

SHA-1_ produces the 160 bit digest of a message.

    >>> from Crypto.Hash import SHA
    >>>
    >>> h = SHA.new()
    >>> h.update(b'Hello')
    >>> print h.hexdigest()

*SHA* stands for Secure Hash Algorithm.

This algorithm is not considered secure. Do not use it for new designs.

.. _SHA-1: http://csrc.nist.gov/publications/fips/fips180-2/fips180-2.pdf
"""

_revision__ = "$Id$"

__all__ = ['new', 'digest_size', 'SHA1Hash' ]

from Crypto.Util.py3compat import *
from Crypto.Hash.hashalgo import HashAlgo

try:
    # The sha module is deprecated in Python 2.6, so use hashlib when possible.
    import hashlib
    hashFactory = hashlib.sha1

except ImportError:
    import sha
    hashFactory = sha

class SHA1Hash(HashAlgo):
    """Class that implements a SHA-1 hash
    
    :undocumented: block_size
    """

    #: ASN.1 Object identifier (OID)::
    #:
    #:  id-sha1    OBJECT IDENTIFIER ::= {
    #:      iso(1) identified-organization(3) oiw(14) secsig(3)
    #:       algorithms(2) 26
    #:  }
    #:
    #: This value uniquely identifies the SHA-1 algorithm.
    oid = b('\x06\x05\x2b\x0e\x03\x02\x1a')

    digest_size = 20
    block_size = 64

    def __init__(self, data=None):
        HashAlgo.__init__(self, hashFactory, data)

    def new(self, data=None):
        return SHA1Hash(data)

def new(data=None):
    """Return a fresh instance of the hash object.

    :Parameters:
       data : byte string
        The very first chunk of the message to hash.
        It is equivalent to an early call to `SHA1Hash.update()`.
        Optional.

    :Return: A `SHA1Hash` object
    """
    return SHA1Hash().new(data)

#: The size of the resulting hash in bytes.
digest_size = SHA1Hash.digest_size

#: The internal block size of the hash algorithm in bytes.
block_size = SHA1Hash.block_size