1 2 :mod:`sha` --- SHA-1 message digest algorithm 3 ============================================= 4 5 .. module:: sha 6 :synopsis: NIST's secure hash algorithm, SHA. 7 :deprecated: 8 .. sectionauthor:: Fred L. Drake, Jr. <fdrake (a] acm.org> 9 10 11 .. deprecated:: 2.5 12 Use the :mod:`hashlib` module instead. 13 14 .. index:: 15 single: NIST 16 single: Secure Hash Algorithm 17 single: checksum; SHA 18 19 This module implements the interface to NIST's secure hash algorithm, known as 20 SHA-1. SHA-1 is an improved version of the original SHA hash algorithm. It is 21 used in the same way as the :mod:`md5` module: use :func:`new` to create an sha 22 object, then feed this object with arbitrary strings using the :meth:`update` 23 method, and at any point you can ask it for the :dfn:`digest` of the 24 concatenation of the strings fed to it so far. SHA-1 digests are 160 bits 25 instead of MD5's 128 bits. 26 27 28 .. function:: new([string]) 29 30 Return a new sha object. If *string* is present, the method call 31 ``update(string)`` is made. 32 33 The following values are provided as constants in the module and as attributes 34 of the sha objects returned by :func:`new`: 35 36 37 .. data:: blocksize 38 39 Size of the blocks fed into the hash function; this is always ``1``. This size 40 is used to allow an arbitrary string to be hashed. 41 42 43 .. data:: digest_size 44 45 The size of the resulting digest in bytes. This is always ``20``. 46 47 An sha object has the same methods as md5 objects: 48 49 50 .. method:: sha.update(arg) 51 52 Update the sha object with the string *arg*. Repeated calls are equivalent to a 53 single call with the concatenation of all the arguments: ``m.update(a); 54 m.update(b)`` is equivalent to ``m.update(a+b)``. 55 56 57 .. method:: sha.digest() 58 59 Return the digest of the strings passed to the :meth:`update` method so far. 60 This is a 20-byte string which may contain non-ASCII characters, including null 61 bytes. 62 63 64 .. method:: sha.hexdigest() 65 66 Like :meth:`digest` except the digest is returned as a string of length 40, 67 containing only hexadecimal digits. This may be used to exchange the value 68 safely in email or other non-binary environments. 69 70 71 .. method:: sha.copy() 72 73 Return a copy ("clone") of the sha object. This can be used to efficiently 74 compute the digests of strings that share a common initial substring. 75 76 77 .. seealso:: 78 79 `Secure Hash Standard <http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf>`_ 80 The Secure Hash Algorithm is defined by NIST document FIPS PUB 180-2: `Secure 81 Hash Standard 82 <http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf>`_, 83 published in August 2002. 84 85 `Cryptographic Toolkit (Secure Hashing) <http://csrc.nist.gov/CryptoToolkit/tkhash.html>`_ 86 Links from NIST to various information on secure hashing. 87 88
