[pycrypto] Docs/code mis-match - not specifying IV fails

[Hugh Macdonald]

Hi Charley,

Thanks for clarifying that - that makes sense to me.


Cheers

Hugh


On 8 January 2014 00:59, Charley Nibley <cnibley at gmail.com> wrote:

> Hi Hugh,
>
> This behavior you are seeing is expected.  It changed with a fix to
> prevent an empty string IV passed to the function. IV is always mandatory
> even if at some point in a previous build it was being passed as all
> zeros.  I believe the doc just needs updating.
>
> See line 173:
> https://github.com/dlitz/pycrypto/commit/411f60f58cea79f7e93476ba0c069b80a2a4c1a0
>
> And see the comments here: https://bugs.launchpad.net/pycrypto/+bug/997464
>
> Charley Nibley
>
>
> On Tue, Jan 7, 2014 at 9:43 AM, Hugh Macdonald <
> hugh.macdonald at nvizible.com> wrote:
>
>> Hi,
>>
>> I've just been trying to figure out why some code of mine broke after an
>> update from 2.0.1 to 2.6.1, and found that I hadn't been passing an IV into
>> AES.new() (using MODE_CFB).
>>
>> Previously, it was happy with this, and, according to the docs here (
>> https://www.dlitz.net/software/pycrypto/api/current/), "It is optional
>> and when not present it will be given a default value of all zeroes."
>>
>> Looking at the code that throws the exception (
>> https://github.com/dlitz/pycrypto/blob/master/src/block_template.c, line
>> 163), it doesn't allow for doing what the docs suggest it will.
>>
>> I'm not sure whether I've either misunderstood something or which of the
>> two is wrong, but I thought I'd at least flag it for discussion...
>>
>>
>> Hugh
>>
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