Other Directory Sites: SeekWonder | Directory Owners Forum
The following archive was created by hippie-mail 7.98617-22 on Thu May 27 1999 - 23:44:20
Bruce Schneier (schneier@counterpane.com)
Fri, 02 Apr 1999 09:13:57 -0600
At 12:19 AM 4/2/99 -0800, Alex Alten wrote:
>I haven't read all our literature over the years, is there a particular
>piece that we published that mentions the word? Certainly I have
>never considered it to be unbreakable, and I have been intimately
>involved with its design, implementation and evolution for several years.
>
>It occurs to me that you and I are saying the same thing, but disagreeing
>about the definition of what a "Vernam cipher" means. So let me precisely
>define what I mean when I say it. To me the core enciphering operation of
>one is the following:
>
> X[i] + Y[i] = Z[i]
>
>Where X[i] is a random byte, Y[i] is the cleartext byte, and Z[i] is
>the cipher text byte. And i goes from 0 to n-1 bytes (n = message length).
>In practice the "+" is ones complement addition, i.e. an exclusive OR
>operation.
>
>For each byte i then you have a simple algebraic equation with two
>unknowns, X and Y. The essence of a Vernam cipher is constructing
>the random sequence of X[i] bytes properly in order to compute the
>equation, i.e. encipher the Y[i] into the Z[i] bytes.
>
>Since RC4 is constructing X[i] byte by byte from a randomly shuffled 256
>byte array of numbers (which is reshuffled over time), I consider it to be
>a type of Vernam cipher. RKS uses a different technique to construct
>the sequence of random X[i] bytes. So it too, I consider to be a type
>of Vernam cipher.
You are free to consider it to be what you like, but you have to understand
that you will continue to be ridiculed in the community. RC4 is an OFB
stream cipher. So is whatever-it-is that you use.
Bruce
**********************************************************************
Bruce Schneier, President, Counterpane Systems Phone: 612-823-1098
101 E Minnehaha Parkway, Minneapolis, MN 55419 Fax: 612-823-1590
Free crypto newsletter. See: http://www.counterpane.com
The following archive was created by hippie-mail 7.98617-22 on Thu May 27 1999 - 23:44:20