So much changes but human nature is to look to the past to conclude
what must be the future.

As my nation goes through changes I want to make the point to you that
what you think is possible may simply be what you have seen before, and
what is actually possible, may be what you cannot imagine.

I imagine.

My journey has been about going from hypothetical to reality, from
dreams of success to accomplishments so great that they are difficult
to grasp, even by me.

Moving forward there will be less of the brainstorming, casting about,
and direct communication that has made the early part of this journey
such a trial.

As time progresses I can escape this dungeon and move beyond postings,
so I guess later I'll never make a direct posting like this, and even
if something ends up on Usenet it will go past some committee
first--people who will make sure the message is the "correct" one and
that there is some message that I stay on, and that I don't stick my
foot into some pile of dung.

Hi,

if the DES model is defined as C = M + K, where + is XOR and C is the
encryption of M under K.

how can i prove that:

__ __ __
C = M + K,

using the identity:
_____ __
A + B = A + B

any help would be appreciated

Hi all,

I was wondering if the following is possible using a symmetric cipher
in general, and in a block-chaining mode in particular:

Suppose a message is encrypted twice; first with key X and then with
key Y.

To decrypt, first the "outer" encryption is undone using key Y, and
then the "inner" encryption is undone using key X.

What I am trying to find is some operation using key X that undoes the
"inner" encryption with key X, without undoing the "outer" encryption
first.

If this is possible, this would allow a re-encryption scheme using
symmetric encryption, without needing to decrypt to the plaintext
first:

E(E(M, X), Y) => (magic operation =>) E(M, Y) => (re-encrypt =>) E(E(M,
Y), Z)

Somewhere i doubt that this is possible, but I figured it can't hurt to
ask :-)

Thanks in advance for thinking about this,
Robert

Hi all,

I was wondering if the following is possible using a symmetric cipher
in general, and in a block-chaining mode in particular:

Suppose a message is encrypted twice; first with key X and then with
key Y.

To decrypt, first the "outer" encryption is undone using key Y, and
then the "inner" encryption is undone using key X.

What I am trying to find is some operation using key X that undoes the
"inner" encryption with key X, without undoing the "outer" encryption
first.

If this is possible, this would allow a re-encryption scheme using
symmetric encryption, without needing to decrypt to the plaintext
first:

E(E(M, X), Y) => (magic operation =>) E(M, Y) => (re-encrypt =>) E(E(M,
Y), Z)

Somewhere i doubt that this is possible, but I figured it can't hurt to
ask :-)

Thanks in advance for thinking about this,
Robert