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56 lines
1.9 KiB
TeX
56 lines
1.9 KiB
TeX
\section{\module{sha} ---
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SHA 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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This module implements the interface to NIST's\index{NIST} secure hash
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algorithm,\index{Secure Hash Algorithm} known as SHA. It is used in
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the same way as the \refmodule{md5} module:\ use the \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 contatenation of the strings fed to it
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so far.\index{checksum!SHA} SHA digests are 160 bits instead of 128
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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}{digestsize}
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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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A sha object has all the methods the md5 objects have, plus one:
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\begin{methoddesc}[sha]{hexdigest}{}
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Return the digest value as a string of 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{seealso}
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\seetext{The Secure Hash Algorithm is defined by NIST document FIPS
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PUB 180-1: \citetitle{Secure Hash Standard}, published in April
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of 1995. It is available online as plain text at
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\url{http://csrc.nist.gov/fips/fip180-1.txt} (at least one
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diagram was omitted) and as PostScript at
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\url{http://csrc.nist.gov/fips/fip180-1.ps}.}
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\end{seealso}
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