[pycrypto] documentation for PKCS1_PSS.py is incorrect, plus minor issue w/ _slowmath.py

[Dwayne C. Litzenberger]

On Wed, May 23, 2012 at 10:48:03AM -0700, Gurney, John-Mark wrote:
>https://github.com/dlitz/pycrypto/blob/master/lib/Crypto/Signature/PKCS1_PSS.py
>
>In the file on lines 41 & 42 it has:
>>>> signer = PKCS1_PSS.new(key)
>>>> signature = PKCS1_PSS.sign(key)
>
>The second line is incorrect.  It should be:
>>>> signature = signer.sign(h)

I've committed a fix.  Thanks!

>Oh, there is also a bogus assertion in _slowmath.py:
>https://github.com/dlitz/pycrypto/blob/master/lib/Crypto/PublicKey/_slowmath.py
>
>On line 85, it asserts that e is long.  If you have an e of 3, it is reasonable for e to be a normal int, and not a long.  Maybe the asserts should be changed to:
>n = long(n)
>e = long(e)
>
>So that python will convert the types properly.

No, those assertions in _slowmath are there so that we catch usage that 
would break when using _fastmath.

_fastmath.rsa_construct (which is written in C) requires long parameters in 
order to keep the C code simple.  If we do the implicit conversions in 
_slowmath, we should also have do the conversions in _fastmath.  Since 
_fastmath is an internal module, I see no reason for the added complexity 
(and risk of bugs).

Cheers,
- Dwayne

-- 
Dwayne C. Litzenberger <dlitz at dlitz.net>
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