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The following archive was created by hippie-mail 7.98617-22 on Thu May 27 1999 - 23:44:21
Mok-Kong Shen (mok-kong.shen@stud.uni-muenchen.de)
Wed, 07 Apr 1999 18:02:15 +0200
staym@accessdata.com wrote:
>
> Geez, how many times do we have to go thru this?
>
> >However, on p.21 of the Handbook by Menezes et al. one reads:
>
> > 1.39 Definition. The Vernam Cipher is a stream cipher defined
> > on the alphabet A = {0,1}. A binary message m_1,m_2,... m_t
> > is operated on by a binary key string k_1,k_2,... k_t of the
> > same length to produce a ciphertext string c_1,c_2,... c_t
> > where
> > c_i = m_i (+) k_i 1 <= i <= t
> > If the key string is randomly chosen and never used again, the
> > Vernam cipher is called a one-time system or a one-time pad.
>
> THE KEY IS THE SAME LENGTH AS THE MESSAGE!!!, not some
> pseudo-random stream generated from fewer key-bits. A Vernam
> Cipher is a stream cipher, and a one-time-pad is a stream cipher, and
> the Vernam Cipher is a one-time-pad, but a stream cipher is NOT
> NECESSARILY A ONE-TIME-PAD ( == Vernam Cipher) UNLESS YOU
> XOR YOUR MESSAGE WITH RANDOM BITS (and the only way
> we know how to get those is from physical chaotic sources) THUS
> MAKING THE RANDOM BITS A KEY THE SIZE OF YOUR MESSAGE!
>
> Now _please_, let this thread die.
Did I say anything against your 'THE KEY IS THE SAME LENGTH AS THE
MESSAGE!!!' ???
Did I employ the word 'pseudo-random' ???
According to Menezes et al. a Vernam Cipher is not necessarily
a one-time pad, contradicting your claim!
I was citing a book to point out some apparent misunderstandings
of terminology (an issue which some people attach very high weight)
in some recent discussions in this group. (Or did you happen to
have missed these?) Please read my original message carefully before
writing comments against it.
M. K. Shen
The following archive was created by hippie-mail 7.98617-22 on Thu May 27 1999 - 23:44:21