[PYTHON-CRYPTO] high-performance HMAC module

[Paul Lambert]

> -----Original Message-----
> From: Jason R. Mastaler [mailto:jason-list-python-crypto at MASTALER.COM]

> >> would be worth writing an HMAC module in C.
> >
> > No, not for this purpose.  It would be better to move to a real
> > encryption algorithm (like AES) written in C than to use p2.
> 
> I think you misunderstood my question.  I'm not using p2.  But p2
> contains a pure-python HMAC module similar to the one that I'm using
> (which I've attached below).

Oops, yes.  

> 
> What I'm asking is whether I will experience a considerable speedup by
> using an HMAC module written in C instead.  Perhaps this isn't worth
> the effort to write such a module since the underlying modules (sha,
> md5) that HMAC uses are already written in C.

Not sure .... it might help for help for very long strings.  For long files you'd still be making be HMACing in chunks/lines so it would not help much.

Paul

> 
> Thanks.
> 
> ---- cut here ----
> 
> # -*- python -*-
> #
> # Copyright (C) 2001,2002 Jason R. Mastaler <jason at mastaler.com>
> #
> # This file is part of TMDA.
> #
> # TMDA is free software; you can redistribute it and/or modify it
> # under the terms of the GNU General Public License as published by
> # the Free Software Foundation; either version 2 of the License, or
> # (at your option) any later version.  A copy of this license should
> # be included in the file COPYING.
> #
> # TMDA is distributed in the hope that it will be useful, but WITHOUT
> # ANY WARRANTY; without even the implied warranty of 
> MERCHANTABILITY or
> # FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General 
> Public License
> # for more details.
> #
> # You should have received a copy of the GNU General Public License
> # along with TMDA; if not, write to the Free Software 
> Foundation, Inc.,
> # 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
> 
> """
> HMAC (Keyed-Hashing for Message Authentication) in Python.
> 
> Implements the HMAC algorithm for SHA-1 as described by
> RFC 2104 (http://www.faqs.org/rfcs/rfc2104.html).
> 
> Python >= 2.2 includes a more general purpose HMAC module
> (http://www.python.org/doc/current/lib/module-hmac.html).
> """
> 
> from array import array
> import sha
> 
> 
> _ipad="\x36"*64
> _opad="\x5C"*64
> 
> _itrans = array('B', [0]*256)
> _otrans = array('B', [0]*256)
> for i in xrange(256):
>     _itrans[i] = i ^ 0x36
>     _otrans[i] = i ^ 0x5c
> _itrans = _itrans.tostring()
> _otrans = _otrans.tostring()
> 
> newh = sha.new
> 
> class hmac:
>     def __init__(self, k, m=None):
>         if isinstance(k, hmac):
>             self.inner = k.inner.copy()
>             self.outer = k.outer.copy()
>         else:
>             self.outer = newh()
>             self.inner = newh()
>             if len(k) > 64:
>                 k=newh(k).digest()
>             k = k + chr(0)*(64-len(k))
>             self.inner.update((k.translate(_itrans)+_ipad)[:64])
>             self.outer.update((k.translate(_otrans)+_opad)[:64])
>             if (m):
>                 self.update(m)
>     def update(self, m):
>         self.inner.update(m)
>     def digest(self):
>         h=self.outer.copy()
>         h.update(self.inner.digest())
>         return h.digest()
> 
> def new(k, m=None):
>     return hmac(k, m)
>