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\section{\module{hmac} ---
Keyed-Hashing for Message Authentication}
\declaremodule{standard}{hmac}
\modulesynopsis{Keyed-Hashing for Message Authentication (HMAC)
implementation for Python.}
\moduleauthor{Gerhard H{\"a}ring}{ghaering@users.sourceforge.net}
\sectionauthor{Gerhard H{\"a}ring}{ghaering@users.sourceforge.net}
\versionadded{2.2}
This module implements the HMAC algorithm as described by \rfc{2104}.
\begin{funcdesc}{new}{key\optional{, msg\optional{, digestmod}}}
Return a new hmac object. If \var{msg} is present, the method call
\code{update(\var{msg})} is made. \var{digestmod} is the digest
module for the HMAC object to use. It defaults to the
\refmodule{md5} module.
\end{funcdesc}
An HMAC object has the following methods:
\begin{methoddesc}[hmac]{update}{msg}
Update the hmac object with the string \var{msg}. Repeated calls
are equivalent to a single call with the concatenation of all the
arguments: \code{m.update(a); m.update(b)} is equivalent to
\code{m.update(a + b)}.
\end{methoddesc}
\begin{methoddesc}[hmac]{digest}{}
Return the digest of the strings passed to the \method{update()}
method so far. This is a 16-byte string (for \refmodule{md5}) or a
20-byte string (for \refmodule{sha}) which may contain non-\ASCII{}
characters, including NUL bytes.
\end{methoddesc}
\begin{methoddesc}[hmac]{hexdigest}{}
Like \method{digest()} except the digest is returned as a string of
length 32 for \refmodule{md5} (40 for \refmodule{sha}), containing
only hexadecimal digits. This may be used to exchange the value
safely in email or other non-binary environments.
\end{methoddesc}
\begin{methoddesc}[hmac]{copy}{}
Return a copy (``clone'') of the hmac object. This can be used to
efficiently compute the digests of strings that share a common
initial substring.
\end{methoddesc}