[pycrypto] Typo or bug?

[Dave Pawson]

On 26 June 2012 10:52, Legrandin <gooksankoo at hoiptorrow.mailexpire.com> wrote:
>>   encobj = AES.new(secret, AES.MODE_CFB)
>>   File "/usr/lib64/python2.7/site-packages/Crypto/Cipher/blockalgo.py",
>> line 141, in __init__
>>   self._cipher = factory.new(key, *args, **kwargs)
>> ValueError: IV must be 16 bytes long
>>
>> So although the 'secret' is 16 bytes long, I'm getting a report saying it
>> isn't?
>>
>
> Hi Dave,
>
> The key is OK, but the IV is missing and it is mandatory for CFB.
> Your code should be:
>
> encobj = AES.new(secret, AES.MODE_CFB, some_iv)
>
> where len(some_iv)==16.

I think I have it working....

  myiv = "some Random string"   # which is 16 bytes long....
  encobj = AES.new(secret, AES.MODE_CFB, myiv)

Would someone help me understand what is happening here please?

I'm guessing on both encode and decode the 'myiv' string should be identical...
but I'm unsure?
https://www.dlitz.net/software/pycrypto/api/current/Crypto.Cipher.AES-module.html#new
shows it in use, but with no explanation?

TIA







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Dave Pawson
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