<!DOCTYPE html PUBLIC
"-//W3C//DTD HTML 4.0 Transitional//EN">
<link rel=
"STYLESHEET" href=
"lib.css" type='text/css'
/>
<link rel=
"SHORTCUT ICON" href=
"../icons/pyfav.png" type=
"image/png" />
<link rel='start' href='../index.html' title='Python Documentation Index'
/>
<link rel=
"first" href=
"lib.html" title='Python Library Reference'
/>
<link rel='contents' href='contents.html'
title=
"Contents" />
<link rel='index' href='genindex.html' title='Index'
/>
<link rel='last' href='about.html' title='About this document...'
/>
<link rel='help' href='about.html' title='About this document...'
/>
<link rel=
"next" href=
"module-md5.html" />
<link rel=
"prev" href=
"crypto.html" />
<link rel=
"parent" href=
"crypto.html" />
<link rel=
"next" href=
"module-md5.html" />
<meta name='aesop' content='information'
/>
<title>15.1 hmac -- Keyed-Hashing for Message Authentication
</title>
<div id='top-navigation-panel' xml:id='top-navigation-panel'
>
<table align=
"center" width=
"100%" cellpadding=
"0" cellspacing=
"2">
<td class='online-navigation'
><a rel=
"prev" title=
"15. Cryptographic Services"
href=
"crypto.html"><img src='../icons/previous.png'
border='
0' height='
32' alt='Previous Page' width='
32'
/></A></td>
<td class='online-navigation'
><a rel=
"parent" title=
"15. Cryptographic Services"
href=
"crypto.html"><img src='../icons/up.png'
border='
0' height='
32' alt='Up One Level' width='
32'
/></A></td>
<td class='online-navigation'
><a rel=
"next" title=
"15.2 md5 "
href=
"module-md5.html"><img src='../icons/next.png'
border='
0' height='
32' alt='Next Page' width='
32'
/></A></td>
<td align=
"center" width=
"100%">Python Library Reference
</td>
<td class='online-navigation'
><a rel=
"contents" title=
"Table of Contents"
href=
"contents.html"><img src='../icons/contents.png'
border='
0' height='
32' alt='Contents' width='
32'
/></A></td>
<td class='online-navigation'
><a href=
"modindex.html" title=
"Module Index"><img src='../icons/modules.png'
border='
0' height='
32' alt='Module Index' width='
32'
/></a></td>
<td class='online-navigation'
><a rel=
"index" title=
"Index"
href=
"genindex.html"><img src='../icons/index.png'
border='
0' height='
32' alt='Index' width='
32'
/></A></td>
<div class='online-navigation'
>
<b class=
"navlabel">Previous:
</b>
<a class=
"sectref" rel=
"prev" href=
"crypto.html">15. Cryptographic Services
</A>
<b class=
"navlabel">Up:
</b>
<a class=
"sectref" rel=
"parent" href=
"crypto.html">15. Cryptographic Services
</A>
<b class=
"navlabel">Next:
</b>
<a class=
"sectref" rel=
"next" href=
"module-md5.html">15.2 md5
</A>
<!--End of Navigation Panel-->
<H1><A NAME=
"SECTION0017100000000000000000">
15.1 <tt class=
"module">hmac
</tt> --
Keyed-Hashing for Message Authentication
</A>
<A NAME=
"module-hmac"></A>
<span class=
"versionnote">New in version
2.2.
</span>
This module implements the HMAC algorithm as described by
<a class=
"rfc" id='rfcref-
92061' xml:id='rfcref-
92061'
href=
"http://www.faqs.org/rfcs/rfc2104.html">RFC
2104</a>.
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
4807' xml:id='l2h-
4807'
class=
"function">new
</tt></b>(
</nobr></td>
<td><var>key
</var><big>[
</big><var>, msg
</var><big>[
</big><var>, digestmod
</var><big>]
</big><var></var><big>]
</big><var></var>)
</td></tr></table></dt>
Return a new hmac object. If
<var>msg
</var> is present, the method call
<code>update(
<var>msg
</var>)
</code> is made.
<var>digestmod
</var> is the digest
module for the HMAC object to use. It defaults to the
<tt class=
"module"><a href=
"module-md5.html">md5
</a></tt> module.
An HMAC object has the following methods:
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
4808' xml:id='l2h-
4808'
class=
"method">update
</tt></b>(
</nobr></td>
<td><var>msg
</var>)
</td></tr></table></dt>
Update the hmac object with the string
<var>msg
</var>. Repeated calls
are equivalent to a single call with the concatenation of all the
arguments:
<code>m.update(a); m.update(b)
</code> is equivalent to
<code>m.update(a + b)
</code>.
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
4809' xml:id='l2h-
4809'
class=
"method">digest
</tt></b>(
</nobr></td>
<td><var></var>)
</td></tr></table></dt>
Return the digest of the strings passed to the
<tt class=
"method">update()
</tt>
method so far. This is a
16-byte string (for
<tt class=
"module"><a href=
"module-md5.html">md5
</a></tt>) or a
20-byte string (for
<tt class=
"module"><a href=
"module-sha.html">sha
</a></tt>) which may contain non-ASCII
characters, including NUL bytes.
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
4810' xml:id='l2h-
4810'
class=
"method">hexdigest
</tt></b>(
</nobr></td>
<td><var></var>)
</td></tr></table></dt>
Like
<tt class=
"method">digest()
</tt> except the digest is returned as a string of
length
32 for
<tt class=
"module"><a href=
"module-md5.html">md5
</a></tt> (
40 for
<tt class=
"module"><a href=
"module-sha.html">sha
</a></tt>), containing
only hexadecimal digits. This may be used to exchange the value
safely in email or other non-binary environments.
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
4811' xml:id='l2h-
4811'
class=
"method">copy
</tt></b>(
</nobr></td>
<td><var></var>)
</td></tr></table></dt>
Return a copy (``clone'') of the hmac object. This can be used to
efficiently compute the digests of strings that share a common
<div class='online-navigation'
>
<table align=
"center" width=
"100%" cellpadding=
"0" cellspacing=
"2">
<td class='online-navigation'
><a rel=
"prev" title=
"15. Cryptographic Services"
href=
"crypto.html"><img src='../icons/previous.png'
border='
0' height='
32' alt='Previous Page' width='
32'
/></A></td>
<td class='online-navigation'
><a rel=
"parent" title=
"15. Cryptographic Services"
href=
"crypto.html"><img src='../icons/up.png'
border='
0' height='
32' alt='Up One Level' width='
32'
/></A></td>
<td class='online-navigation'
><a rel=
"next" title=
"15.2 md5 "
href=
"module-md5.html"><img src='../icons/next.png'
border='
0' height='
32' alt='Next Page' width='
32'
/></A></td>
<td align=
"center" width=
"100%">Python Library Reference
</td>
<td class='online-navigation'
><a rel=
"contents" title=
"Table of Contents"
href=
"contents.html"><img src='../icons/contents.png'
border='
0' height='
32' alt='Contents' width='
32'
/></A></td>
<td class='online-navigation'
><a href=
"modindex.html" title=
"Module Index"><img src='../icons/modules.png'
border='
0' height='
32' alt='Module Index' width='
32'
/></a></td>
<td class='online-navigation'
><a rel=
"index" title=
"Index"
href=
"genindex.html"><img src='../icons/index.png'
border='
0' height='
32' alt='Index' width='
32'
/></A></td>
<div class='online-navigation'
>
<b class=
"navlabel">Previous:
</b>
<a class=
"sectref" rel=
"prev" href=
"crypto.html">15. Cryptographic Services
</A>
<b class=
"navlabel">Up:
</b>
<a class=
"sectref" rel=
"parent" href=
"crypto.html">15. Cryptographic Services
</A>
<b class=
"navlabel">Next:
</b>
<a class=
"sectref" rel=
"next" href=
"module-md5.html">15.2 md5
</A>
<span class=
"release-info">Release
2.4.2, documentation updated on
28 September
2005.
</span>
<!--End of Navigation Panel-->
See
<i><a href=
"about.html">About this document...
</a></i> for information on suggesting changes.