Cryptography-Digest Digest #899, Volume #10 Thu, 13 Jan 00 17:13:01 EST
Contents:
Re: "1:1 adaptive huffman compression" doesn't work (Mok-Kong Shen)
Re: LSFR (Terje Mathisen)
Re: AES & satellite example (Greg)
Re: Is SSL really this slow? (Greg)
<!-- To use a different cobrand, make sure you have a template for it in
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Re: Blum, Blum, Shub generator (lcs Mixmaster Remailer)
Re: Why is EDI dead? Is S/MIME 'safe'? Who and why? (James Redfern)
Re: Why is EDI dead? Is S/MIME 'safe'? Who and why? (James Redfern)
----------------------------------------------------------------------------
From: Mok-Kong Shen <[EMAIL PROTECTED]>
Subject: Re: "1:1 adaptive huffman compression" doesn't work
Date: Thu, 13 Jan 2000 22:30:45 +0100
SCOTT19U.ZIP_GUY wrote:
>
> If the one intercepting konws your compression program there has to
> be a means to seperate where the compression ends and the random
> data begins. If one does that then the added random information did nothing.
> Better to use a 1-1 compression where the data is compressed to fit the
> spave available and where no extra info is added. Since the decompression
> program most be able to seperate out this random stuff anyway.
Sorry, I don't yet understand. The compression software is public.
Everyone can have it. Yes, the software has the additional work
to get appropriate filling bits and to put these in on compression
and to throw these away on decompression. (The software 'knows'
how it is to be done.) But are you arguing that's too much
computational work or what? I don't think that's too much work.
I have never said that my proposal is 'better' than any 1-1
compression scheme, only that it 'suffices' for the (practical)
purpose at hand. Now that you and some people else have developed
1-1 compressors, one can certainly (or even better) use these (at
least theoretically more satisfying) products. But on retrospect,
if my proposal were put forth earlier, there would be in my humble
view no absolute 'necessity' to develop the 1-1 compressors, as far
'practical needs' (in contrast to theoretical desires) are concerned.
Have I explained the essential points of a previous follow-up
clearly enough here?
M. K. Shen
------------------------------
From: Terje Mathisen <[EMAIL PROTECTED]>
Subject: Re: LSFR
Date: Thu, 13 Jan 2000 22:23:27 +0100
Trevor Jackson, III wrote:
> Afterthought: I believe the GPS systems uses a PRNG as a kind of time base.
> They do this to avoid putting a ridiculously accurate clock in each receiver.
> You might find something useful in the research behind their system.
> Unfortunately I don't have any references at hand.
That's not totally correct:
GPS uses a 1023-bit direct sequence spreading code to transmit really
low baud rate information using a power level which is well down in the
background noise at the receiver end.
Since the receivers know the 32 (?) possible spreading codes, they can
try to locate a signal by logically sliding a local copy of the code
along the received signal, when/if they match up, you have found a
satellite, and (not incidentially), you have also established a fairly
good time reference, i.e. the transmitter frequency +/- any doppler
shift.
The GPS receivers don't need extremely accurate clocks, because they
only need to measure the differences in propagation time from the
current set of satellites.
They still have very good crystals though, much better than what's used
on a PC motherboard.
These crystals must be stable enough to measure short time intervals
with nanosecond precision, if they had a local atomic clock, then you
could get a 3D position fix from just 3 satellites. Instead you use one
more bird to effectively synthesize a local atomic clock. This approach
is what makes it possible for a Motorola Oncore UT+ to deliver UTC time
with about 30 ns RMS precision.
Anyway, you're welcome to step over to comp.protocols.time.ntp or
sci.geo.satellite-nav, both of them are frequented by people who like to
discuss this stuff.
Terje
--
- <[EMAIL PROTECTED]>
Using self-discipline, see http://www.eiffel.com/discipline
"almost all programming can be viewed as an exercise in caching"
------------------------------
From: Greg <[EMAIL PROTECTED]>
Subject: Re: AES & satellite example
Date: Thu, 13 Jan 2000 21:25:05 GMT
> > But an expensive mil bird would be a very strong candidate. Or do
> > you think that the military would use something other than AES
> > finalists?
>
> "Military" satellites are certainly not going to use an AES finalist.
> Why should they? You already can't crack their encryption.
Do you mean that military ciphers are way ahead of public ciphers
or that they simply see no reason to use a published cipher?
Sent via Deja.com http://www.deja.com/
Before you buy.
------------------------------
From: Greg <[EMAIL PROTECTED]>
Subject: Re: Is SSL really this slow?
Date: Thu, 13 Jan 2000 21:29:40 GMT
> > In the process of integrating SSL into some software that uses
> > sockets, I was surprised to see more than a 10 fold decrease in
> > speed. At this time, my testing is allowing all traffic to be
> > encrypted. Most of it does not need to be, but it is impossible
> > for our software to distinguish between standard marshaling packet
> > information and any confidential data that is embedded in the
> > packets, since we are approaching this integration at a low level.
> >
> > So my question is this: If I were to transmit 250k across a wire
> > and it took about one second, is it reasonable to assume that
> > SSL can slow this transmission down to require 10 seconds? Or
> > is this too slow that I am most likely doing something wrong?
>
> There is definitely something wrong. If you are noticing you
> machine getting it's CPU thrashed, you are probably doing something
> like sending lots of small SSL messages.
>
> Some SSL implementations send a SSL packet with each call to the
> SSL_write function. The encryption of 1000 8 byte packs is a similar
> cost to encrypting 1 8000 byte record. The MAC is not.
> When using RC4, on most CPU's, the message checksums (MAC) is more
> expensive than encryption. For small messages eg, on a pentium II-
350,
> type 8 bytes 64 bytes 256 bytes 1024 bytes
8192 bytes
> md5 4386.43k 22556.08k 41630.81k 52626.15k
57733.02k
> hmac(md5) 1346.23k 9053.11k 24628.91k 43307.22k
55924.05k
> This means that if you are generating message digests, one per 8
bytes,
> your throughput will be 4400k/s. If using 8k blocks, 52600k/s.
> If you used 4 bytes, 2200k/s, 2 bytes, 1100k/s, you get the idea.
>
> Anyway, lots of small write kill SSLv3 and do much worse on TLS,
since it uses
> the HMAC construct, which as you can see above is much worse :-).
>
> These number indicate that performance should not be too bad, but
depending on
> the CPU and network, it does make a difference.
> Another issue can be cause by the TCP protocol which normally hates
multiple
> packets being sent in one direction without messages in the other
direction.
> Depending on the implementation, time-outs slow things down allot.
>
> So, anyway, if the small messages is you problem, you need to just
insert a
> 'buffering' layer above you SSL_write type function and performance
should
> greatly improve.
>
> eric (who knows lots of ways to make SSL run slowly, and also how to
speed it
> up :-)
>
Well, I just got it running yesterday (not knowing much about
it to begin with), and then this morning I looked at it again and
discovered that the CPU was basically idling >90% of the time.
So I seriously doubt it is an encryption issue. I think the SSL
library that I am trying to use is doing something with the socket
that I am just not anticipating.
The ref doc is vague, to say the least. Without source code, I
cannot look inside the library and see what it is doing or why.
--
The only vote that you waste is the one you never wanted to make.
RICO- we were told it was a necessary surrender of our civil liberties.
Asset Forfeiture- the latest inevitable result of RICO.
http://www.ciphermax.com/book
Sent via Deja.com http://www.deja.com/
Before you buy.
------------------------------
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Date: 13 Jan 2000 21:40:16 -0000
From: lcs Mixmaster Remailer <[EMAIL PROTECTED]>
Subject: Re: Blum, Blum, Shub generator
Every time this topic comes up, there is incredible misinformation spewed.
Choose BBS as a good RSA modulus, with p and q congruent to 3 mod 4.
Choose a random x, and start with x_0 = x^2. That's all you need to do.
Concerns about cycle lengths are misplaced. If there is a significant
chance of choosing a random x_0 which leads to a short cycle, you can
factor n. Here's how.
Choose an x at random such that the Jacobi symbol (x / n) = -1, therefore
x is not a quadratic residue. Set x_0 = x^2 mod n. Then find a short
cycle leading back to x_0. This is possible, if short cycles are a
concern at all.
You now know two square roots of x_0: x, and the last element in the cycle
before x_0. These are distinct because x is not a quadratic residue and
the cycle element is. Knowing two square roots allows you to factor n,
by doing gcd of the sum of the two square roots and n. This is exactly
the same as the chosen-ciphertext attack against Rabin encryption.
Therefore, it follows from the RSA assumption that finding short cycles
is impossible, for moduli large enough that factorization is intractable.
This is not an asymptotic result, it applies to specific moduli of 512
or 1024 bits. If any one of those has a short cycle that can be found in
a tractable amount of time, it can be factored. That's the bottom line.
The advice to choose moduli with guaranteed long cycles, and to choose
seeds that way, is completely useless. It is like the advice you
used to hear to choose "strong" RSA moduli by careful choice of p and q.
No one does this any more, because it has been proven to be pointless.
The attacks this was meant to protect against are not effective against
moduli of the sizes in use today.
The same thing is true of concern about cycle lengths. Factoring RSA
moduli by trying to guess values with short cycles is an inefficient
way of attacking the problem. That's why the RSA factoring efforts
don't use this algorithm, they use NFS and related algorithms instead.
Worry about cycle lengths is nothing more or less than superstition.
And don't get me started on checking that x is not a multiple of p or q...
;-)
------------------------------
From: James Redfern <[EMAIL PROTECTED]>
Crossposted-To: comp.security.misc,alt.security.pgp
Subject: Re: Why is EDI dead? Is S/MIME 'safe'? Who and why?
Date: Thu, 13 Jan 2000 20:17:27 +0000
Reply-To: James Redfern <redfern[AT]privacyx[DOT]com>
On Thu, 13 Jan 2000 12:42:19 -0500, "Richard A. Schulman"
<[EMAIL PROTECTED]> wrote:
| Whether The Redfern Organization will turn my prognostication into a
| successful IPO I will leave to your better judgment, but I always welcome
| consultancy fees....
Hey, no problemo. Write your name on a blank signed check, send it to me and
I'll fill it out for whatever you tell me you want.
| Hey, isn't this way off topic for these newsgroups?
It is now we've left out the XML and S/MIME stuff.
JR.
--
James Redfern <[EMAIL PROTECTED]> The Redfern Organization
PGP key ID 0x8244C43A from <mailto:[EMAIL PROTECTED]?subject=0x8244C43A>
...ActiveNames delivers my undeliverable mail at <www.ActiveNames.com>
------------------------------
From: James Redfern <[EMAIL PROTECTED]>
Crossposted-To: comp.security.misc,alt.security.pgp
Subject: Re: Why is EDI dead? Is S/MIME 'safe'? Who and why?
Date: Thu, 13 Jan 2000 20:22:23 +0000
Reply-To: James Redfern <redfern[AT]privacyx[DOT]com>
On Fri, 14 Jan 2000 00:43:36 +0800, sb5309 <[EMAIL PROTECTED]> wrote:
| What is "remote document processing business - invoices, price-lists,
| technical drawings etc." ?
|
| I am curious. Thanks.
It's part of remote publishing which can be for a reason of 'logistics'. For
example, 'USA Today' has been operating multiple printing plants across the US
to print their nationally-distributed paper near where it is to be delivered.
You can access your corporate WAN and print documents at any office in the
country. This is really handy as you get a better quality document for folks
at the remote office to look at than I can by faxing it and it takes less
time. But what if I wanted to ensure that only one copy was made? Then
connecting to the remote printer and transmitting the job would be one way of
being reasonably sure that only one original copy was printed. The printer
might be in a book store and I might be printing a book on site. Also, as its
effective span of operation becomes global, e-Commerce businesses will start
to need remote, variable output and billing as they evolve from their current
'centralist' modality. You don't need to bring the goods from Taiwan to the
US in order to ship them back to your Japanese or Chinese customers. But your
US web-site does need to have a method to produce your Taiwan warehouse
pick-list and billing documents in Mandarin and Kanji. Hence the "remote
document processing business - invoices, price-lists,technical drawings etc."
JR.
--
James Redfern <[EMAIL PROTECTED]> The Redfern Organization
PGP key ID 0x8244C43A from <mailto:[EMAIL PROTECTED]?subject=0x8244C43A>
...ActiveNames delivers my undeliverable mail at <www.ActiveNames.com>
------------------------------
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