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91 lines
2.9 KiB
TeX
91 lines
2.9 KiB
TeX
\section{\module{md5} ---
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MD5 message digest algorithm}
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\declaremodule{builtin}{md5}
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\modulesynopsis{RSA's MD5 message digest algorithm.}
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This module implements the interface to RSA's MD5 message digest
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\index{message digest, MD5}
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algorithm (see also Internet \rfc{1321}). Its use is quite
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straightforward:\ use \function{new()} to create an md5 object.
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You can now feed this object with arbitrary strings using the
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\method{update()} method, and at any point you can ask it for the
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\dfn{digest} (a strong kind of 128-bit checksum,
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a.k.a. ``fingerprint'') of the concatenation of the strings fed to it
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so far using the \method{digest()} method.
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\index{checksum!MD5}
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For example, to obtain the digest of the string \code{'Nobody inspects
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the spammish repetition'}:
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\begin{verbatim}
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>>> import md5
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>>> m = md5.new()
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>>> m.update("Nobody inspects")
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>>> m.update(" the spammish repetition")
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>>> m.digest()
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'\xbbd\x9c\x83\xdd\x1e\xa5\xc9\xd9\xde\xc9\xa1\x8d\xf0\xff\xe9'
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\end{verbatim}
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More condensed:
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\begin{verbatim}
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>>> md5.new("Nobody inspects the spammish repetition").digest()
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'\xbbd\x9c\x83\xdd\x1e\xa5\xc9\xd9\xde\xc9\xa1\x8d\xf0\xff\xe9'
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\end{verbatim}
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The following values are provided as constants in the module and as
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attributes of the md5 objects returned by \function{new()}:
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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{16}.
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\end{datadesc}
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md5 objects support the following methods:
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\begin{funcdesc}{new}{\optional{arg}}
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Return a new md5 object. If \var{arg} is present, the method call
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\code{update(\var{arg})} is made.
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\end{funcdesc}
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\begin{funcdesc}{md5}{\optional{arg}}
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For backward compatibility reasons, this is an alternative name for the
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\function{new()} function.
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\end{funcdesc}
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An md5 object has the following methods:
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\begin{methoddesc}[md5]{update}{arg}
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Update the md5 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}[md5]{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 16-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}[md5]{hexdigest}{}
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Like \method{digest()} except the digest is returned as a string of
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length 32, 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}[md5]{copy}{}
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Return a copy (``clone'') of the md5 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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\seemodule{sha}{Similar module implementing the Secure Hash
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Algorithm (SHA). The SHA algorithm is considered a
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more secure hash.}
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\end{seealso}
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