Re: Stream cipher against block cipher

From: AE (hidden_at_nospam.com)
Date: 06/27/03 

Date: Fri, 27 Jun 2003 22:35:31 +0200

Douglas A. Gwyn wrote:
> AE wrote:
>
>>Douglas A. Gwyn wrote:
>>
>>>AE wrote:
>>>
>>>>You can create a stream cipher from a block cipher by running it in CTR,
>>>>OFB or CFB mode, but it is not that simple to construct a block cipher
>>>
>>>>from a stream cipher.
>>>Actually it's easier.
>>
>>Well - I followed the thread concerning how to create a block cipher
>>from a stream cipher, but nothing I've seen there looked promising:
>
>
> Just use the stream cipher to encrypt successive units in each block.

This doesn't make a block cipher.

>>>>Most stream ciphers don't allow you to add a IV ...
>>>
>>>Sure they do.
>>
>>Which ones? SEAL? RC4? WAKE? any LFSR-construction?
>
> Any of them Just transmit the IV before the data. For a typical
> stream cipher, that scrambles the internal state.

No it doesn't: For SEAL, RC4 and all LFSR-constructions I know this
wouldn't effect the remaining ciphertext at all.

> ...

AE

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