Re: Sun setting on stream ciphers?

From: Mok-Kong Shen (mok-kong.shen_at_t-online.de)
Date: 02/29/04

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    Date: Sun, 29 Feb 2004 12:19:13 +0100

    Douglas A. Gwyn wrote:

    > It has been pointed out before that the distinction
    > between "stream cipher" and "block cipher" is rather
    > artificial, and that each can be used in the role of
    > the other.
    >

    Yes, absolutely. If one chooses a larger unit, say 128
    bits, and employs a number of rounds and additionally
    uses a PRNG to generate bits to do xoring and/or to
    influence the processing in other ways (e.g. selection
    of S-boxes or doing byte permuations), then the result
    of such combination of stream and block processing
    techniques (I had a humble design of this kind several
    years ago, see my old webpage) certainly isn't a (pure)
    'stream cipher' or a (pure) 'block cipher' in the 'narrow'
    definitions one often encounters in discussions. On
    the other hand, 'stream ciphers' seem to be generally
    characterized by their design simplicity and hence
    higher speed. An example is RC4. However, I have the
    impression that some newer designs of 'stream ciphers'
    being proposed aren't very simple. One might probably
    then question why 'block ciphers' (especially in CTR
    mode) aren't to be preferred instead.

    M. K. Shen
    ------------------------------------
    http://home.t-online.de/home/mok-kong.shen

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