[PYTHON-CRYPTO] PEP-272 Deficiencies - Comments

[Janusz A. Urbanowicz]

Paul wrote/napisał[a]/schrieb:
> At 3:54 PM -0700 12/15/01, Jason R. Mastaler wrote:
> >phr-pycrypt at nightsong.com writes:
> >
> >>  Is a draft copy of PEP 272 actually available somewhere?
> >
> >http://python.sourceforge.net/peps/pep-0272.html
> 
> This api has several problems:
> 
> 1) I agree with Janusz A. Urbanowicz's earlier note that symmetric
> encryption should be a class.  The initialization can give it the
> key.  Note that it may later need to be reinitialized, so a
>       set_key(key)  method should also be available and the initialization
>                     should be optional (but raise an exception on use when no
>                     key is available)
 
I don't like it very much. This breaks the OO design view - any instance of
CIpher is a cipher with a particular key. If you want to change the key,
yopu create a new instacne of the class.

If there is absolutely a must of some set_key method, it should return a new
instance of the class, not reset the live object.
 
> 2) The modes of operation should not be parameters. The modes create
> new algorithms types.  It's easy to spin out new mode algorithms with
> a mode "wrapper" class.

Agreed. I thought of it that way: there are three base classes: Cipher for
symmetric key, Encryptor for pubkey and Hash for hashes. Any given cipher
algorithm is a subclass of Cipher etc. A variation of algorithm is a subclass
of base cipher. So it would be that 3DES-CBC is a subclass of 3DES, which is a
subclass of DES which is a subclass of Cipher.

Alex

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