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| 17 | <title>15.1 hmac -- Keyed-Hashing for Message Authentication</title> |
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| 55 | <H1><A NAME="SECTION0017100000000000000000"> |
| 56 | 15.1 <tt class="module">hmac</tt> -- |
| 57 | Keyed-Hashing for Message Authentication</A> |
| 58 | </H1> |
| 59 | |
| 60 | <P> |
| 61 | <A NAME="module-hmac"></A> |
| 62 | |
| 63 | <P> |
| 64 | |
| 65 | <span class="versionnote">New in version 2.2.</span> |
| 66 | |
| 67 | <P> |
| 68 | This module implements the HMAC algorithm as described by <a class="rfc" id='rfcref-92061' xml:id='rfcref-92061' |
| 69 | href="http://www.faqs.org/rfcs/rfc2104.html">RFC 2104</a>. |
| 70 | |
| 71 | <P> |
| 72 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 73 | <td><nobr><b><tt id='l2h-4807' xml:id='l2h-4807' class="function">new</tt></b>(</nobr></td> |
| 74 | <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> |
| 75 | <dd> |
| 76 | Return a new hmac object. If <var>msg</var> is present, the method call |
| 77 | <code>update(<var>msg</var>)</code> is made. <var>digestmod</var> is the digest |
| 78 | module for the HMAC object to use. It defaults to the |
| 79 | <tt class="module"><a href="module-md5.html">md5</a></tt> module. |
| 80 | </dl> |
| 81 | |
| 82 | <P> |
| 83 | An HMAC object has the following methods: |
| 84 | |
| 85 | <P> |
| 86 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 87 | <td><nobr><b><tt id='l2h-4808' xml:id='l2h-4808' class="method">update</tt></b>(</nobr></td> |
| 88 | <td><var>msg</var>)</td></tr></table></dt> |
| 89 | <dd> |
| 90 | Update the hmac object with the string <var>msg</var>. Repeated calls |
| 91 | are equivalent to a single call with the concatenation of all the |
| 92 | arguments: <code>m.update(a); m.update(b)</code> is equivalent to |
| 93 | <code>m.update(a + b)</code>. |
| 94 | </dl> |
| 95 | |
| 96 | <P> |
| 97 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 98 | <td><nobr><b><tt id='l2h-4809' xml:id='l2h-4809' class="method">digest</tt></b>(</nobr></td> |
| 99 | <td><var></var>)</td></tr></table></dt> |
| 100 | <dd> |
| 101 | Return the digest of the strings passed to the <tt class="method">update()</tt> |
| 102 | method so far. This is a 16-byte string (for <tt class="module"><a href="module-md5.html">md5</a></tt>) or a |
| 103 | 20-byte string (for <tt class="module"><a href="module-sha.html">sha</a></tt>) which may contain non-ASCII |
| 104 | characters, including NUL bytes. |
| 105 | </dl> |
| 106 | |
| 107 | <P> |
| 108 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 109 | <td><nobr><b><tt id='l2h-4810' xml:id='l2h-4810' class="method">hexdigest</tt></b>(</nobr></td> |
| 110 | <td><var></var>)</td></tr></table></dt> |
| 111 | <dd> |
| 112 | Like <tt class="method">digest()</tt> except the digest is returned as a string of |
| 113 | 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 |
| 114 | only hexadecimal digits. This may be used to exchange the value |
| 115 | safely in email or other non-binary environments. |
| 116 | </dl> |
| 117 | |
| 118 | <P> |
| 119 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 120 | <td><nobr><b><tt id='l2h-4811' xml:id='l2h-4811' class="method">copy</tt></b>(</nobr></td> |
| 121 | <td><var></var>)</td></tr></table></dt> |
| 122 | <dd> |
| 123 | Return a copy (``clone'') of the hmac object. This can be used to |
| 124 | efficiently compute the digests of strings that share a common |
| 125 | initial substring. |
| 126 | </dl> |
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