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A new hashlib module to replace the md5 and sha modules. It adds support for additional secure hashes such as SHA-256 and SHA-512. The hashlib module uses OpenSSL for fast platform optimized implementations of algorithms when available. The old md5 and sha modules still exist as wrappers around hashlib to preserve backwards compatibility.
83 lines
2.9 KiB
TeX
83 lines
2.9 KiB
TeX
\section{\module{sha} ---
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SHA-1 message digest algorithm}
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\declaremodule{builtin}{sha}
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\modulesynopsis{NIST's secure hash algorithm, SHA.}
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\sectionauthor{Fred L. Drake, Jr.}{fdrake@acm.org}
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\deprecated{2.5}{Use the \refmodule{hashlib} module instead.}
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This module implements the interface to NIST's\index{NIST} secure hash
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algorithm,\index{Secure Hash Algorithm} known as SHA-1. SHA-1 is an
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improved version of the original SHA hash algorithm. It is used in
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the same way as the \refmodule{md5} module:\ use \function{new()}
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to create an sha object, then feed this object with arbitrary strings
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using the \method{update()} method, and at any point you can ask it
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for the \dfn{digest} of the concatenation of the strings fed to it
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so far.\index{checksum!SHA} SHA-1 digests are 160 bits instead of
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MD5's 128 bits.
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\begin{funcdesc}{new}{\optional{string}}
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Return a new sha object. If \var{string} is present, the method
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call \code{update(\var{string})} is made.
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\end{funcdesc}
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The following values are provided as constants in the module and as
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attributes of the sha objects returned by \function{new()}:
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\begin{datadesc}{blocksize}
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Size of the blocks fed into the hash function; this is always
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\code{1}. This size is used to allow an arbitrary string to be
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hashed.
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\end{datadesc}
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\begin{datadesc}{digest_size}
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The size of the resulting digest in bytes. This is always
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\code{20}.
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\end{datadesc}
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An sha object has the same methods as md5 objects:
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\begin{methoddesc}[sha]{update}{arg}
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Update the sha object with the string \var{arg}. Repeated calls are
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equivalent to a single call with the concatenation of all the
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arguments: \code{m.update(a); m.update(b)} is equivalent to
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\code{m.update(a+b)}.
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\end{methoddesc}
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\begin{methoddesc}[sha]{digest}{}
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Return the digest of the strings passed to the \method{update()}
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method so far. This is a 20-byte string which may contain
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non-\ASCII{} characters, including null bytes.
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\end{methoddesc}
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\begin{methoddesc}[sha]{hexdigest}{}
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Like \method{digest()} except the digest is returned as a string of
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length 40, containing only hexadecimal digits. This may
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be used to exchange the value safely in email or other non-binary
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environments.
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\end{methoddesc}
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\begin{methoddesc}[sha]{copy}{}
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Return a copy (``clone'') of the sha object. This can be used to
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efficiently compute the digests of strings that share a common initial
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substring.
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\end{methoddesc}
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\begin{seealso}
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\seetitle[http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf]
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{Secure Hash Standard}
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{The Secure Hash Algorithm is defined by NIST document FIPS
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PUB 180-2:
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\citetitle[http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf]
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{Secure Hash Standard}, published in August 2002.}
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\seetitle[http://csrc.nist.gov/encryption/tkhash.html]
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{Cryptographic Toolkit (Secure Hashing)}
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{Links from NIST to various information on secure hashing.}
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\end{seealso}
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