SHA-based encryption function in Python

[Paul Rubin]

bryanjugglercryptographer at yahoo.com (Bryan Olson) writes:
> Not so good.  The attacker only has to guess one block to break
> all subsequent blocks.  For a demo, put the code below into 
> the p2.py file

ARGGH!  I knew about that before too, but forgot about it while writing
the code.  I will replace SHA(block) with SHA(key + block) and release
a new version tonight, with the MAC improved too.  Sound ok?

Thanks.