Cryptography-Digest Digest #149, Volume #14 Sun, 15 Apr 01 10:13:01 EDT
Contents:
Advantages of attackers and defenders (Mok-Kong Shen)
Remark on multiplication mod 2^n (Mok-Kong Shen)
Re: XOR_TextBox: Doesn't write to swap file if... (Anthony Stephen Szopa)
Re: Remark on multiplication mod 2^n ("Tom St Denis")
Re: XOR_TextBox: Doesn't write to swap file if... ("Tom St Denis")
Re: Remark on multiplication mod 2^n (Mok-Kong Shen)
Re: Remark on multiplication mod 2^n (Mok-Kong Shen)
Note on combining PRNGs with the method of Wichmann and Hill (Mok-Kong Shen)
Re: Remark on multiplication mod 2^n ("Tom St Denis")
Re: Note on combining PRNGs with the method of Wichmann and Hill ("Tom St Denis")
Re: Remark on multiplication mod 2^n (Mok-Kong Shen)
Re: Note on combining PRNGs with the method of Wichmann and Hill (Mok-Kong Shen)
Re: XOR_TextBox: Doesn't write to swap file if... ("Sam Simpson")
Re: XOR_TextBox: Doesn't write to swap file if... ("Sam Simpson")
Re: XOR_TextBox: Doesn't write to swap file if... ("Sam Simpson")
Re: Remark on multiplication mod 2^n ("Tom St Denis")
Re: Note on combining PRNGs with the method of Wichmann and Hill ("Tom St Denis")
C code for GF mults ("Tom St Denis")
Re: Remark on multiplication mod 2^n (Mok-Kong Shen)
Re: Remark on multiplication mod 2^n ("Tom St Denis")
Re: Remark on multiplication mod 2^n (Mok-Kong Shen)
Re: MS OSs "swap" file: total breach of computer security. ("Joris Dobbelsteen")
----------------------------------------------------------------------------
From: Mok-Kong Shen <[EMAIL PROTECTED]>
Subject: Advantages of attackers and defenders
Date: Sun, 15 Apr 2001 14:13:56 +0200
There is an interesting article in the April issue of Bruce
Schneier's Crypto-Gram where it is argued about the relative
adavantages of attackers and defenders of internet security
employing analogies from actual (physical) wars.
It is my humble opinion that general conclusions about which
side of a war has more advantages may be difficult to
establish, since each war has its (under circumstances
rather odd) particularities. Anyway, defenders in cyberwar
certainly wouldn't have a light job, if one considers
the extremely huge sum that, according to a newspaper
article I recently read, the United States plan to expend
in that connection.
M. K. Shen
------------------------------
From: Mok-Kong Shen <[EMAIL PROTECTED]>
Subject: Remark on multiplication mod 2^n
Date: Sun, 15 Apr 2001 14:13:49 +0200
If one has two n-bit entities a and b, then one can obtain
from them a nonlinear combination a*b mod 2^n. As pointed
out in a recent thread (by David Wagner?), the higher order
bits of the operands have less contribution to the result
than the lower order bits. A trivial and ad hoc remedy that
suggests itself seems to be to do first a full multiplication,
obtaining c*2^n + d and define the result to be either
c + d mod 2^n or c xor d. This full multiplication could be
done in high-level programming language, but can be more
efficiently performed with an assembler code exploiting the
appropriate hardware support (a register containing c) which
is commonly present (if I don't err).
I like to mention an additional operation that could be
useful in this connection, namely rotation. One could
place two masks (5 bits if n=32) on the operands a and b
to obtain two values as the amounts of rotation, the value
from a being used to rotate b and the value from b being
used to rotate a. The rotated results are then multiplied
as described above.
M. K. Shen
================================
http://home.t-online.de/home/mok-kong.shen
------------------------------
From: Anthony Stephen Szopa <[EMAIL PROTECTED]>
Crossposted-To: talk.politics.crypto,alt.hacker
Subject: Re: XOR_TextBox: Doesn't write to swap file if...
Date: Sun, 15 Apr 2001 05:21:14 -0700
"Trevor L. Jackson, III" wrote:
>
> Fair Warning (for the uninformed): This software is garbage. The author
> does not understand computers, software, or security.
>
> Anthony Stephen Szopa wrote:
>
> > XOR_TextBox: Doesn't write to swap file if...
> >
> > Excerpt from updated Version 1.2 Instructions:
> >
> > "I have a 256MB RAM computer running Windows '98. When I run
> > XOR_TextBox there is no writing to the WIN386.SWP swap file. In
> > other words, the entered or displayed text is only stored in RAM.
> > If you have less RAM, the text you enter or display may be written
> > to this swap file. Because you normally have no control over or
> > access to this swap file, writing to it may be an unacceptable
> > security risk.
> >
> > Here is how you can check to see if your computer is writing to the
> > WIN386.SWP swap file when using XOR_TextBox on your computer..."
> >
> > In Version 1.1 a progress bar was added to the status bar, and an XOR
> > process completion notification was also added to the status bar.
> >
> > In Version 1.2 additional help and explanations were added to
> > the Instructions clarifying any swap file issue..
> >
> > Thanks for all of your feedback.
> >
> > Cheers.
FUD.
Give us a reasonable explanation or scenario why or when XOR_TextBox
will write to the swap file?
I can: when the machine has relatively little RAM. One of my
computers has only 64MBs and it always writes to the swap file with
XOR_TextBox. But my 256MB computer never does.
XOR_TextBox provides instructions on how to check your swap file to
see if it is being written to when running XOR_TextBox. It either
is or it isn't.
Some flaky posters would have us believe they would be running
trajectory simulations for future space flights to Uranus in their
computer's back ground while they run XOR_TextBox on a 1000 node
intranet from a server.
The software is designed for a stand alone computer. The
instructions specifically say not to run other programs when
using XOR_TextBox.
Well, by implication you must know more than me because you seem to
feel you are qualified to judge me.
Since you are so smart, tell everyone how to crack OAP-L3.
------------------------------
From: "Tom St Denis" <[EMAIL PROTECTED]>
Subject: Re: Remark on multiplication mod 2^n
Date: Sun, 15 Apr 2001 13:01:16 GMT
"Mok-Kong Shen" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]...
>
> If one has two n-bit entities a and b, then one can obtain
> from them a nonlinear combination a*b mod 2^n. As pointed
> out in a recent thread (by David Wagner?), the higher order
> bits of the operands have less contribution to the result
> than the lower order bits. A trivial and ad hoc remedy that
> suggests itself seems to be to do first a full multiplication,
> obtaining c*2^n + d and define the result to be either
> c + d mod 2^n or c xor d. This full multiplication could be
> done in high-level programming language, but can be more
> efficiently performed with an assembler code exploiting the
> appropriate hardware support (a register containing c) which
> is commonly present (if I don't err).
>
> I like to mention an additional operation that could be
> useful in this connection, namely rotation. One could
> place two masks (5 bits if n=32) on the operands a and b
> to obtain two values as the amounts of rotation, the value
> from a being used to rotate b and the value from b being
> used to rotate a. The rotated results are then multiplied
> as described above.
Unless you use a field (instead of a ring) multiplication is a not a good
diffusion primitive at all. Preferably if you use GF(2^W) with a secret
multiplicand... :-)
Tom
------------------------------
From: "Tom St Denis" <[EMAIL PROTECTED]>
Crossposted-To: talk.politics.crypto,alt.hacker
Subject: Re: XOR_TextBox: Doesn't write to swap file if...
Date: Sun, 15 Apr 2001 13:02:17 GMT
"Anthony Stephen Szopa" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]...
> "Trevor L. Jackson, III" wrote:
> >
> > Fair Warning (for the uninformed): This software is garbage. The
author
> > does not understand computers, software, or security.
> >
> > Anthony Stephen Szopa wrote:
> >
> > > XOR_TextBox: Doesn't write to swap file if...
> > >
> > > Excerpt from updated Version 1.2 Instructions:
> > >
> > > "I have a 256MB RAM computer running Windows '98. When I run
> > > XOR_TextBox there is no writing to the WIN386.SWP swap file. In
> > > other words, the entered or displayed text is only stored in RAM.
> > > If you have less RAM, the text you enter or display may be written
> > > to this swap file. Because you normally have no control over or
> > > access to this swap file, writing to it may be an unacceptable
> > > security risk.
> > >
> > > Here is how you can check to see if your computer is writing to the
> > > WIN386.SWP swap file when using XOR_TextBox on your computer..."
> > >
> > > In Version 1.1 a progress bar was added to the status bar, and an XOR
> > > process completion notification was also added to the status bar.
> > >
> > > In Version 1.2 additional help and explanations were added to
> > > the Instructions clarifying any swap file issue..
> > >
> > > Thanks for all of your feedback.
> > >
> > > Cheers.
>
>
> FUD.
>
> Give us a reasonable explanation or scenario why or when XOR_TextBox
> will write to the swap file?
>
> I can: when the machine has relatively little RAM. One of my
> computers has only 64MBs and it always writes to the swap file with
> XOR_TextBox. But my 256MB computer never does.
That's BS. My 384mb machine right now has 100mb used and does swap to
disk.... and I only have winamp+icq+msie+this+tiny+virusscanner in memory.
> XOR_TextBox provides instructions on how to check your swap file to
> see if it is being written to when running XOR_TextBox. It either
> is or it isn't.
Why not just avoid using swappable memory/
Tom
------------------------------
From: Mok-Kong Shen <[EMAIL PROTECTED]>
Subject: Re: Remark on multiplication mod 2^n
Date: Sun, 15 Apr 2001 15:08:08 +0200
Tom St Denis wrote:
>
[snip]
> Unless you use a field (instead of a ring) multiplication is a not a good
> diffusion primitive at all. Preferably if you use GF(2^W) with a secret
> multiplicand... :-)
As I said, it's something ad hoc. It's simple to do,
'perfection' was not the goal.
M. K. Shen
------------------------------
From: Mok-Kong Shen <[EMAIL PROTECTED]>
Subject: Re: Remark on multiplication mod 2^n
Date: Sun, 15 Apr 2001 15:12:02 +0200
Mok-Kong Shen wrote:
>
> Tom St Denis wrote:
> >
> [snip]
> > Unless you use a field (instead of a ring) multiplication is a not a good
> > diffusion primitive at all. Preferably if you use GF(2^W) with a secret
> > multiplicand... :-)
>
> As I said, it's something ad hoc. It's simple to do,
> 'perfection' was not the goal.
Addendum: In the context of intended applications both
operands of multiplication are generally 'secret'.
M. K. Shen
------------------------------
From: Mok-Kong Shen <[EMAIL PROTECTED]>
Crossposted-To: sci.crypt.random-numbers
Subject: Note on combining PRNGs with the method of Wichmann and Hill
Date: Sun, 15 Apr 2001 15:13:33 +0200
The method of Wichmann and Hill (Appl. Statist. 31 (1982))
for combining n arbitrary PRNGs with output in [0, 1) consists
in forming their sum mod 1. For crypto purposes, one could
introduce some 'variability' by employing a weighted sum
instead, thus rendering the analysis more difficult. We could,
for example, choose cofficients in some range (1.0-delta,
1.0+delta) to multiply the PRNG outputs before summing mod 1.
Further, some of the PRNG outputs may be squared before
addition, thus creating nonlinearity (most PRNGs commonly
employed in numerical computations are linear, though they
have very good properties like large periods and simplicity
of implementation). Of course, weighted sum could also
be done on integer pseudo-random number sequences.
M. K. Shen
==============================
http://home.t-online.de/home/mok-kong.shen
------------------------------
From: "Tom St Denis" <[EMAIL PROTECTED]>
Subject: Re: Remark on multiplication mod 2^n
Date: Sun, 15 Apr 2001 13:24:10 GMT
"Mok-Kong Shen" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]...
>
>
> Mok-Kong Shen wrote:
> >
> > Tom St Denis wrote:
> > >
> > [snip]
> > > Unless you use a field (instead of a ring) multiplication is a not a
good
> > > diffusion primitive at all. Preferably if you use GF(2^W) with a
secret
> > > multiplicand... :-)
> >
> > As I said, it's something ad hoc. It's simple to do,
> > 'perfection' was not the goal.
>
> Addendum: In the context of intended applications both
> operands of multiplication are generally 'secret'.
Ahh but with mults in GF(2^W) you have the property that all output bits
generally depend on all input bits *and* if you use a function like "ax + b"
where (a, b) are random you have function immune to first order
differential/linear attacks!
Tom
------------------------------
From: "Tom St Denis" <[EMAIL PROTECTED]>
Crossposted-To: sci.crypt.random-numbers
Subject: Re: Note on combining PRNGs with the method of Wichmann and Hill
Date: Sun, 15 Apr 2001 13:26:02 GMT
"Mok-Kong Shen" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]...
>
> The method of Wichmann and Hill (Appl. Statist. 31 (1982))
> for combining n arbitrary PRNGs with output in [0, 1) consists
> in forming their sum mod 1. For crypto purposes, one could
> introduce some 'variability' by employing a weighted sum
> instead, thus rendering the analysis more difficult. We could,
> for example, choose cofficients in some range (1.0-delta,
> 1.0+delta) to multiply the PRNG outputs before summing mod 1.
> Further, some of the PRNG outputs may be squared before
> addition, thus creating nonlinearity (most PRNGs commonly
> employed in numerical computations are linear, though they
> have very good properties like large periods and simplicity
> of implementation). Of course, weighted sum could also
> be done on integer pseudo-random number sequences.
One could idea is to think of 0..1 as 0..65535 (i.e fixed point of 0.16)
It's mathmatically similar and provides reasonably more efficient study.
In this case you see that you don't perform (prng)/(2^w) to get 0..1 you
just take the output directly (note the attacker could just mult your value
by 2^w to get the real values.)
Tom
------------------------------
From: Mok-Kong Shen <[EMAIL PROTECTED]>
Subject: Re: Remark on multiplication mod 2^n
Date: Sun, 15 Apr 2001 15:35:00 +0200
Tom St Denis wrote:
>
> Ahh but with mults in GF(2^W) you have the property that all output bits
> generally depend on all input bits *and* if you use a function like "ax + b"
> where (a, b) are random you have function immune to first order
> differential/linear attacks!
You seemed to have ignored my word 'simplicity' and
no intention of 'perfection'. What if W is 32 or 64?
M. K. Shen
------------------------------
From: Mok-Kong Shen <[EMAIL PROTECTED]>
Crossposted-To: sci.crypt.random-numbers
Subject: Re: Note on combining PRNGs with the method of Wichmann and Hill
Date: Sun, 15 Apr 2001 15:35:07 +0200
Tom St Denis wrote:
>
> One could idea is to think of 0..1 as 0..65535 (i.e fixed point of 0.16)
> It's mathmatically similar and provides reasonably more efficient study.
> In this case you see that you don't perform (prng)/(2^w) to get 0..1 you
> just take the output directly (note the attacker could just mult your value
> by 2^w to get the real values.)
PRNGs in numerics are commonly standardized to [0, 1),
even they are at the base generating integers. And
in the general (for crypto more interesting) cases,
they have different integer ranges.
M. K. Shen
------------------------------
From: "Sam Simpson" <[EMAIL PROTECTED]>
Crossposted-To: talk.politics.crypto,alt.hacker
Subject: Re: XOR_TextBox: Doesn't write to swap file if...
Date: Sun, 15 Apr 2001 14:32:20 +0100
Apart from that, would you recommend the software? ;)))))))
--
Regards,
Sam
http://www.scramdisk.clara.net/
Trevor L. Jackson, III <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]...
> Fair Warning (for the uninformed): This software is garbage. The author
> does not understand computers, software, or security.
>
> Anthony Stephen Szopa wrote:
>
> > XOR_TextBox: Doesn't write to swap file if...
> >
> > Excerpt from updated Version 1.2 Instructions:
> >
> > "I have a 256MB RAM computer running Windows '98. When I run
> > XOR_TextBox there is no writing to the WIN386.SWP swap file. In
> > other words, the entered or displayed text is only stored in RAM.
> > If you have less RAM, the text you enter or display may be written
> > to this swap file. Because you normally have no control over or
> > access to this swap file, writing to it may be an unacceptable
> > security risk.
> >
> > Here is how you can check to see if your computer is writing to the
> > WIN386.SWP swap file when using XOR_TextBox on your computer..."
> >
> > In Version 1.1 a progress bar was added to the status bar, and an XOR
> > process completion notification was also added to the status bar.
> >
> > In Version 1.2 additional help and explanations were added to
> > the Instructions clarifying any swap file issue..
> >
> > Thanks for all of your feedback.
> >
> > Cheers.
>
>
>
>
------------------------------
From: "Sam Simpson" <[EMAIL PROTECTED]>
Crossposted-To: talk.politics.crypto,alt.hacker
Subject: Re: XOR_TextBox: Doesn't write to swap file if...
Date: Sun, 15 Apr 2001 14:33:15 +0100
Why don't you code the app so that 'important' areas of memory are never
swapped out? PGP does that kind of thing on Win32..........
--
Regards,
Sam
http://www.scramdisk.clara.net/
Anthony Stephen Szopa <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]...
> XOR_TextBox: Doesn't write to swap file if...
>
> Excerpt from updated Version 1.2 Instructions:
>
> "I have a 256MB RAM computer running Windows '98. When I run
> XOR_TextBox there is no writing to the WIN386.SWP swap file. In
> other words, the entered or displayed text is only stored in RAM.
> If you have less RAM, the text you enter or display may be written
> to this swap file. Because you normally have no control over or
> access to this swap file, writing to it may be an unacceptable
> security risk.
>
> Here is how you can check to see if your computer is writing to the
> WIN386.SWP swap file when using XOR_TextBox on your computer..."
>
> In Version 1.1 a progress bar was added to the status bar, and an XOR
> process completion notification was also added to the status bar.
>
> In Version 1.2 additional help and explanations were added to
> the Instructions clarifying any swap file issue..
>
> Thanks for all of your feedback.
>
> Cheers.
------------------------------
From: "Sam Simpson" <[EMAIL PROTECTED]>
Crossposted-To: talk.politics.crypto,alt.hacker
Subject: Re: XOR_TextBox: Doesn't write to swap file if...
Date: Sun, 15 Apr 2001 14:34:14 +0100
I have 384Mb too and it swaps regularly, even with just a couple of small
apps running..........
--
Regards,
Sam
http://www.scramdisk.clara.net/
Tom St Denis <[EMAIL PROTECTED]> wrote in message
news:tZgC6.12358$[EMAIL PROTECTED]...
>
> "Anthony Stephen Szopa" <[EMAIL PROTECTED]> wrote in message
> news:[EMAIL PROTECTED]...
> > "Trevor L. Jackson, III" wrote:
> > >
> > > Fair Warning (for the uninformed): This software is garbage. The
> author
> > > does not understand computers, software, or security.
> > >
> > > Anthony Stephen Szopa wrote:
> > >
> > > > XOR_TextBox: Doesn't write to swap file if...
> > > >
> > > > Excerpt from updated Version 1.2 Instructions:
> > > >
> > > > "I have a 256MB RAM computer running Windows '98. When I run
> > > > XOR_TextBox there is no writing to the WIN386.SWP swap file. In
> > > > other words, the entered or displayed text is only stored in RAM.
> > > > If you have less RAM, the text you enter or display may be written
> > > > to this swap file. Because you normally have no control over or
> > > > access to this swap file, writing to it may be an unacceptable
> > > > security risk.
> > > >
> > > > Here is how you can check to see if your computer is writing to the
> > > > WIN386.SWP swap file when using XOR_TextBox on your computer..."
> > > >
> > > > In Version 1.1 a progress bar was added to the status bar, and an
XOR
> > > > process completion notification was also added to the status bar.
> > > >
> > > > In Version 1.2 additional help and explanations were added to
> > > > the Instructions clarifying any swap file issue..
> > > >
> > > > Thanks for all of your feedback.
> > > >
> > > > Cheers.
> >
> >
> > FUD.
> >
> > Give us a reasonable explanation or scenario why or when XOR_TextBox
> > will write to the swap file?
> >
> > I can: when the machine has relatively little RAM. One of my
> > computers has only 64MBs and it always writes to the swap file with
> > XOR_TextBox. But my 256MB computer never does.
>
> That's BS. My 384mb machine right now has 100mb used and does swap to
> disk.... and I only have winamp+icq+msie+this+tiny+virusscanner in memory.
>
> > XOR_TextBox provides instructions on how to check your swap file to
> > see if it is being written to when running XOR_TextBox. It either
> > is or it isn't.
>
> Why not just avoid using swappable memory/
>
> Tom
>
>
------------------------------
From: "Tom St Denis" <[EMAIL PROTECTED]>
Subject: Re: Remark on multiplication mod 2^n
Date: Sun, 15 Apr 2001 13:56:37 GMT
"Mok-Kong Shen" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]...
>
>
> Tom St Denis wrote:
> >
>
> > Ahh but with mults in GF(2^W) you have the property that all output bits
> > generally depend on all input bits *and* if you use a function like "ax
+ b"
> > where (a, b) are random you have function immune to first order
> > differential/linear attacks!
>
> You seemed to have ignored my word 'simplicity' and
> no intention of 'perfection'. What if W is 32 or 64?
W can be anything. And GF mults are simple (albeit not super fast). In my
"yet to be submited for SAC" cipher design I use GF mults extensively....
:-)
Tom
------------------------------
From: "Tom St Denis" <[EMAIL PROTECTED]>
Crossposted-To: sci.crypt.random-numbers
Subject: Re: Note on combining PRNGs with the method of Wichmann and Hill
Date: Sun, 15 Apr 2001 13:58:22 GMT
"Mok-Kong Shen" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]...
>
>
> Tom St Denis wrote:
> >
>
> > One could idea is to think of 0..1 as 0..65535 (i.e fixed point of 0.16)
> > It's mathmatically similar and provides reasonably more efficient study.
> > In this case you see that you don't perform (prng)/(2^w) to get 0..1 you
> > just take the output directly (note the attacker could just mult your
value
> > by 2^w to get the real values.)
>
> PRNGs in numerics are commonly standardized to [0, 1),
> even they are at the base generating integers. And
> in the general (for crypto more interesting) cases,
> they have different integer ranges.
My point was that conceptually they are the same but without going to
decimals is easier to cryptanalyze (mainly just faster). It's like say
"1+1+1+1+1" instead of just "5". The result is conceptually the same (and
this case numerically) but the method is diff. Bydoing
a/b, it's the same thing (if you are analyzing a) as ab/b = a since in this
case 'b' is known and fixed it doesn't skew the prng bias much if any at all
Tom
------------------------------
From: "Tom St Denis" <[EMAIL PROTECTED]>
Subject: C code for GF mults
Date: Sun, 15 Apr 2001 14:00:27 GMT
Just to show what a GF mult looks like here is my code I generally use (and
optimize for specific situations when needed).
/* multiply in a and b in GF(2^r) mod p */
word gf_multiply(word p, word r, word a, word b)
{
word shift = b, result = 0;
while (a) {
if (a & 1)
result ^= shift;
a >>= 1;
if (shift & (1ul<<(r-1)))
shift = (shift << 1) ^ p;
else
shift <<= 1;
}
return result;
}
Where "word" is unsigned, unsigned long, etc... as long as it's big
enough...
--
Tom St Denis
---
http://tomstdenis.home.dhs.org
------------------------------
From: Mok-Kong Shen <[EMAIL PROTECTED]>
Subject: Re: Remark on multiplication mod 2^n
Date: Sun, 15 Apr 2001 16:00:06 +0200
Tom St Denis wrote:
>
> "Mok-Kong Shen" <[EMAIL PROTECTED]> wrote:
> > You seemed to have ignored my word 'simplicity' and
> > no intention of 'perfection'. What if W is 32 or 64?
>
> W can be anything. And GF mults are simple (albeit not super fast). In my
> "yet to be submited for SAC" cipher design I use GF mults extensively....
> :-)
Certainly W can be anything. But compare the computing
effort. A Mercedes is better than a small Austin,
but you have also to pay more.
M. K. Shen
------------------------------
From: "Tom St Denis" <[EMAIL PROTECTED]>
Subject: Re: Remark on multiplication mod 2^n
Date: Sun, 15 Apr 2001 14:02:41 GMT
"Mok-Kong Shen" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]...
>
>
> Tom St Denis wrote:
> >
> > "Mok-Kong Shen" <[EMAIL PROTECTED]> wrote:
>
> > > You seemed to have ignored my word 'simplicity' and
> > > no intention of 'perfection'. What if W is 32 or 64?
> >
> > W can be anything. And GF mults are simple (albeit not super fast). In
my
> > "yet to be submited for SAC" cipher design I use GF mults
extensively....
> > :-)
>
> Certainly W can be anything. But compare the computing
> effort. A Mercedes is better than a small Austin,
> but you have also to pay more.
A W-bit GF mult takes W loops thru a small function... where there are W
xors, shifts and "and" operations.
The result is certainly much better than mults in Z mod 2^W ...
------------------------------
From: Mok-Kong Shen <[EMAIL PROTECTED]>
Subject: Re: Remark on multiplication mod 2^n
Date: Sun, 15 Apr 2001 16:04:01 +0200
Tom St Denis wrote:
>
> "Mok-Kong Shen" <[EMAIL PROTECTED]> wrote:
> >
> >
> > Tom St Denis wrote:
> > >
> > > "Mok-Kong Shen" <[EMAIL PROTECTED]> wrote:
> >
> > > > You seemed to have ignored my word 'simplicity' and
> > > > no intention of 'perfection'. What if W is 32 or 64?
> > >
> > > W can be anything. And GF mults are simple (albeit not super fast). In
> my
> > > "yet to be submited for SAC" cipher design I use GF mults
> extensively....
> > > :-)
> >
> > Certainly W can be anything. But compare the computing
> > effort. A Mercedes is better than a small Austin,
> > but you have also to pay more.
>
> A W-bit GF mult takes W loops thru a small function... where there are W
> xors, shifts and "and" operations.
>
> The result is certainly much better than mults in Z mod 2^W ...
Didn't I wrote the word 'better'??
M. K. Shen
------------------------------
From: "Joris Dobbelsteen" <[EMAIL PROTECTED]>
Crossposted-To: talk.politics.crypto,alt.hacker
Subject: Re: MS OSs "swap" file: total breach of computer security.
Date: Sun, 15 Apr 2001 16:08:45 +0200
Swap files are a risk when Windows is NOT in control of them, as long as
Windows controls them they are secure from the outside world.
Encrypting swap files is not only inefficient (without hardware encryption
faster than 50 MB/s), it's also not needed...
Windows 2000 (and probably NT4 also) have a function to create a '0' -ed
pagefile when Windows shuts down gracefully.
Next, access to pagefiles is denied when opening the "pagefile.sys" file
anyway. Hope they didn't forget the back-door: reading data directly from
the disk, e.g. Disk Defragmenter. The disk defragmenter uses a special API,
so access should be denied (am about 100% sure about this). With Windows
running, access to the pagefile is impossible.
The ONLY possible attack is: When Windows is NOT running or the disk has
been dismanteled from the system for analysis on another system.
I expected that it was possible to allocate memory that will NOT be swapped:
not be written to disk. However I'm not sure about completely this.
If you make the correct settings and use NT (9x has NO security at all) it's
only possible to analyse the pagefile if:
* Windows has crashed and has not been rebooted
* The disk with the pagefile has been removed from the system for analysis
and Windows had not been shutted down before removal.
I don't see any problem with the pagefile, explain me, what's wrong?????
Better worry about the insecurity of your payment card, as all your
transactions can be monitored by everybody, your phone can be tapped, your
money on your bank account can be stolen, you car get's stolen more
easily.......... etc. etc...
- Joris
"Anthony Stephen Szopa" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]...
> MS OSs "swap" file: total breach of computer security.
>
> Unbelievable.
>
> For me, the "swap" file implementation in MS OSs is proof positive
> that MS is in a conspiracy to control OUR information (and all of
> US by implication) and is most probably cooperating with the
> government in this regard. MS is intentionally placing our right
> to privacy at risk.
>
> It also tells me that this Justice Dept. anti-trust case against MS
> may be nothing but a political charade.
>
> A computer user must have total discretionary control over certain
> aspects of OS implementation such as the activation, use, and
> access to a "swap" file.
>
> The only discretion one has at this time is to NOT use any leaky MS
> security sieve of an OS.
------------------------------
** FOR YOUR REFERENCE **
The service address, to which questions about the list itself and requests
to be added to or deleted from it should be directed, is:
Internet: [EMAIL PROTECTED]
You can send mail to the entire list by posting to sci.crypt.
End of Cryptography-Digest Digest
******************************
