Cryptography-Digest Digest #129, Volume #10 Sun, 29 Aug 99 07:13:02 EDT
Contents:
Re: n-ary Huffman Template Algorithm (Mok-Kong Shen)
Q: Cross-covariance of independent RN sequences in practice (Mok-Kong Shen)
Re: Can americans export crypto when in another country? (SCOTT19U.ZIP_GUY)
Re: The Reversal of NetNanny (Matthew Skala)
Re: How Easy Can Terrorists Get Strong Encrypt? (Matthew Skala)
Re: NEW THREAD on compression (Mok-Kong Shen)
Cryptography FAQ (01/10: Overview) ([EMAIL PROTECTED])
Cryptography FAQ (02/10: Net Etiquette) ([EMAIL PROTECTED])
----------------------------------------------------------------------------
From: Mok-Kong Shen <[EMAIL PROTECTED]>
Crossposted-To: sci.image.processing,sci.math,alt.comp.compression
Subject: Re: n-ary Huffman Template Algorithm
Date: Sun, 29 Aug 1999 10:29:27 +0200
Alex Vinokur wrote:
> 2. Huffman template algorithm enables
> to use non-numerical weights (costs, frequences).
A question just for my understanding: How can frequencies be
non-numerical at all? If you have a number of frequencies and have
only their ordering according to magnitude but not know their
numerical values, how can you expect to obtain a coding that is
optimal?
M. K. Shen
------------------------------
From: Mok-Kong Shen <[EMAIL PROTECTED]>
Subject: Q: Cross-covariance of independent RN sequences in practice
Date: Sun, 29 Aug 1999 10:15:42 +0200
If one has two independent sequences of uniformly distributed random
numbers, their cross-covariance should theoretically (by definition)
be zero. Because of imperfection in this world, e.g. impossibility of
making objects of exact sizes or attaining the temperature of absolute
zero, I suppose that there is a certain not too small lower bound of
the (average) value of the cross-covariance obtainable in practice.
Does anyone happen to have computed the cross-covariance of
independent very good random number sequences?
A related question concerns the auto-covariance. Does anyone
happen to have such data, say, from sequences obtained from very
good physical sources of noises?
Many thanks in advance.
M. K. Shen
=================================
http://home.t-online.de/home/mok-kong.shen (new addr.)
------------------------------
From: [EMAIL PROTECTED] (SCOTT19U.ZIP_GUY)
Subject: Re: Can americans export crypto when in another country?
Date: Sat, 28 Aug 1999 13:57:47 GMT
In article <[EMAIL PROTECTED]>, "Trevor Jackson, III" <[EMAIL PROTECTED]>
wrote:
>
>
>W.G. Unruh wrote:
>
>> [EMAIL PROTECTED] (Doug Stell) writes:
>>
>> >Unless you give up your U.S. citizenship, doing so would be "U.S.
>> >envolvement" and would be covered under the export regulations. Living
>> >in Canada or marrying a Canadian would make zero difference.
>>
>> Could you give a reference for this in the EAR regulations? Under ITAR,
>> this would be covered under "Technical assistance" which also required a
>> license, but I do not recall seeing such a subsection under EAR.
>> Also, it still has to be "export" of some sort. Ie, if the US citizen
>> could show that the stuff was not even in his head before he left the
>> USA, it would I suspect be hard to get a conviction under the export
>> sections.
>
>Can you outline such a proof? Typically proving a negative is infeasible.
>
>For criminal prosecution it is up to the government to prove that you did
>have it in your head prior to departing the US.
>
Actuall this would only be true if the Constitution still had valitity.
States and Feds routinely violated this trouble some piece of paper
that stands in the way bewteen total governement control and
freedom they are always inventing new classes of crimes such
as infractions which by the definations the governent pulled out
of there ass say that since these are so minor the constitution
does not apply. The camel's nose is in the tent. And the people
are to asleep to push it out.
David A. Scott
--
SCOTT19U.ZIP NOW AVAILABLE WORLD WIDE
http://www.jim.com/jamesd/Kong/scott19u.zip
http://members.xoom.com/ecil/index.htm
NOTE EMAIL address is for SPAMERS
------------------------------
From: [EMAIL PROTECTED] (Matthew Skala)
Subject: Re: The Reversal of NetNanny
Date: 29 Aug 1999 00:53:54 -0700
In article <7psumq$3bp$[EMAIL PROTECTED]>, <[EMAIL PROTECTED]> wrote:
>The essay is called _The Reversal of NetNanny_ and you'll find it at
>http://hem2.passagen.se/eddy1/reveng/nn/
That's an excellent article. If you're looking to improve it, you might
do well to work on the general language quality (difficult if you're not a
native speaker of English, I know). For instance, I caught several
occurances of "or" when I'm pretty sure you meant "our".
I wrote a somewhat more formal paper with some relevance to censorware and
posted it on the Web at http://www.islandnet.com/~mskala/limdiff.html ;
the general theme is, "Okay, so we've seen that what they're doing is the
Wrong Thing, what should they do instead?" Of course, that's for a
definition of "should" that assumes that the goal is for them to protect
their products from reverse engineering. As you point out, it's
impossible to protect an encrypted block list from reverse engineers
because people can just run the software in a debugger and read off the
plaintext data. Storing only hashes, which is something else you
mentioned in your article, is a partial solution, but not good if what the
software is doing is a substring search. I propose a special hash
designed for keyword searching.
One might well ask whether it's a good idea to give the bad people ideas
on how better to repress us, but I address that issue, too, on the page at
the above URL. Anyway, I'll include a link to your article from that page
when I next update it.
--
Matthew Skala "Why should the fates of the groovy
[EMAIL PROTECTED] and the creepy be intertwined?"
http://www.islandnet.com/~mskala/ - Valerie Solanas
------------------------------
From: [EMAIL PROTECTED] (Matthew Skala)
Subject: Re: How Easy Can Terrorists Get Strong Encrypt?
Date: 29 Aug 1999 01:23:29 -0700
In article <7q1efv$8fg$[EMAIL PROTECTED]>, Greg <[EMAIL PROTECTED]> wrote:
>Then there are the religious fanatics. Most of these can safely be
>said not to have much common logic in their thinking, so they would not
>know how to design a flow chart, let alone program a PC in C or BASIC.
I think you've been reading your own propaganda. Never a good idea.
Religious fanatics come in all varieties. Many of them are not stupid in
any obvious way. That's what makes them so dangerous. Lots of people
think I myself am a religious fanatic, for reasons that include but are
not limited to the fact that I oppose abortion on moral grounds. I also
hold other views considerably more shocking to the average person than
that one, but opposing abortion, by itself, is enough for many people to
automatically write me off as a "fanatic". My beliefs don't appear to
interfere with my programming skills; on the contrary, I think my
intellectual and spiritual activities complement and enhance each other.
Now, you probably won't see me tossing any Molotov cocktails at people any
time soon, nor releasing dangerous computer viruses, etc. But it's
perfectly possible to believe that if someone with my DNA were born into a
different cultural situation than I was, that person could grow up to be
what you would call a "terrorist", while still being well able to create
strong cryptographic software.
--
Matthew Skala "Why should the fates of the groovy
[EMAIL PROTECTED] and the creepy be intertwined?"
http://www.islandnet.com/~mskala/ - Valerie Solanas
------------------------------
From: Mok-Kong Shen <[EMAIL PROTECTED]>
Subject: Re: NEW THREAD on compression
Date: Sun, 29 Aug 1999 12:16:04 +0200
SCOTT19U.ZIP_GUY wrote:
>
> if I rewrite this in hex it is easer for me
>
> FF compressed to 00 and decompress FF
> FF decompress to 00 and compresss to FF
.........
Simply because of my curiosity/laziness:
Could you also test the following with your new code?
C1 = 00100100 11111111
C2 = 00100100 11111111 11111111
It would be desirable that some sort of correctness proof of your
modifications to the Huffman algorithm be available. That would
help, I think, finding the answer to your question of determining
the best one-to-one algorithm (delivering the shortest sequence).
M. K. Shen
------------------------------
From: [EMAIL PROTECTED]
Crossposted-To: talk.politics.crypto,sci.answers,news.answers,talk.answers
Subject: Cryptography FAQ (01/10: Overview)
Date: 29 Aug 1999 10:40:42 GMT
Reply-To: [EMAIL PROTECTED]
Archive-name: cryptography-faq/part01
Last-modified: 1999/06/27
This is the first of ten parts of the sci.crypt FAQ. The parts are
mostly independent, but you should read this part before the rest. We
don't have the time to send out missing parts by mail, so don't ask.
Notes such as ``[KAH67]'' refer to the reference list in the last part.
Disclaimer: This document is the product of the Crypt Cabal, a secret
society which serves the National Secu---uh, no. Seriously, we're the
good guys, and we've done what we can to ensure the completeness and
accuracy of this document, but in a field of military and commercial
importance like cryptography you have to expect that some people and
organizations consider their interests more important than open
scientific discussion. Trust only what you can verify firsthand.
And don't sue us.
Many people have contributed to this FAQ. In alphabetical order:
Eric Bach, Steve Bellovin, Dan Bernstein, Nelson Bolyard, Carl Ellison,
Jim Gillogly, Mike Gleason, Doug Gwyn, Luke O'Connor, Tony Patti,
William Setzer. We apologize for any omissions.
Archives: sci.crypt has been archived since October 1991 on
ripem.msu.edu, though these archives are available only to U.S. and
Canadian users. Another site is rpub.cl.msu.edu in /pub/crypt/sci.crypt/
from Jan 1992.
The sections of this FAQ are available via anonymous FTP to rtfm.mit.edu
as /pub/usenet/news.answers/cryptography-faq/part[xx]. The Cryptography
FAQ is posted to the newsgroups sci.crypt, talk.politics.crypto,
sci.answers, and news.answers every 21 days.
The fields `Last-modified' and `Version' at the top of each part track
revisions.
1999: There is a project underway to reorganize, expand, and update the
sci.crypt FAQ, pending the resolution of some minor legal issues. The
new FAQ will have two pieces. The first piece will be a series of web
pages. The second piece will be a short posting, focusing on the
questions that really are frequently asked.
In the meantime, if you need to know something that isn't covered in the
current FAQ, you can probably find it starting from Ron Rivest's links
at <http://theory.lcs.mit.edu/~rivest/crypto-security.html>.
If you have comments on the current FAQ, please post them to sci.crypt
under the subject line Crypt FAQ Comments. (The crypt-comments email
address is out of date.)
Table of Contents
=================
1. Overview
2. Net Etiquette
2.1. What groups are around? What's a FAQ? Who am I? Why am I here?
2.2. Do political discussions belong in sci.crypt?
2.3. How do I present a new encryption scheme in sci.crypt?
3. Basic Cryptology
3.1. What is cryptology? Cryptography? Plaintext? Ciphertext? Encryption? Key?
3.2. What references can I start with to learn cryptology?
3.3. How does one go about cryptanalysis?
3.4. What is a brute-force search and what is its cryptographic relevance?
3.5. What are some properties satisfied by every strong cryptosystem?
3.6. If a cryptosystem is theoretically unbreakable, then is it
guaranteed analysis-proof in practice?
3.7. Why are many people still using cryptosystems that are
relatively easy to break?
3.8. What are the basic types of cryptanalytic `attacks'?
4. Mathematical Cryptology
4.1. In mathematical terms, what is a private-key cryptosystem?
4.2. What is an attack?
4.3. What's the advantage of formulating all this mathematically?
4.4. Why is the one-time pad secure?
4.5. What's a ciphertext-only attack?
4.6. What's a known-plaintext attack?
4.7. What's a chosen-plaintext attack?
4.8. In mathematical terms, what can you say about brute-force attacks?
4.9. What's a key-guessing attack? What's entropy?
5. Product Ciphers
5.1. What is a product cipher?
5.2. What makes a product cipher secure?
5.3. What are some group-theoretic properties of product ciphers?
5.4. What can be proven about the security of a product cipher?
5.5. How are block ciphers used to encrypt data longer than the block size?
5.6. Can symmetric block ciphers be used for message authentication?
5.7. What exactly is DES?
5.8. What is triple DES?
5.9. What is differential cryptanalysis?
5.10. How was NSA involved in the design of DES?
5.11. Is DES available in software?
5.12. Is DES available in hardware?
5.13. Can DES be used to protect classified information?
5.14. What are ECB, CBC, CFB, and OFB encryption?
6. Public-Key Cryptography
6.1. What is public-key cryptography?
6.2. How does public-key cryptography solve cryptography's Catch-22?
6.3. What is the role of the `trapdoor function' in public key schemes?
6.4. What is the role of the `session key' in public key schemes?
6.5. What's RSA?
6.6. Is RSA secure?
6.7. What's the difference between the RSA and Diffie-Hellman schemes?
6.8. What is `authentication' and the `key distribution problem'?
6.9. How fast can people factor numbers?
6.10. What about other public-key cryptosystems?
6.11. What is the `RSA Factoring Challenge?'
7. Digital Signatures
7.1. What is a one-way hash function?
7.2. What is the difference between public, private, secret, shared, etc.?
7.3. What are MD4 and MD5?
7.4. What is Snefru?
8. Technical Miscellany
8.1. How do I recover from lost passwords in WordPerfect?
8.2. How do I break a Vigenere (repeated-key) cipher?
8.3. How do I send encrypted mail under UNIX? [PGP, RIPEM, PEM, ...]
8.4. Is the UNIX crypt command secure?
8.5. How do I use compression with encryption?
8.6. Is there an unbreakable cipher?
8.7. What does ``random'' mean in cryptography?
8.8. What is the unicity point (a.k.a. unicity distance)?
8.9. What is key management and why is it important?
8.10. Can I use pseudo-random or chaotic numbers as a key stream?
8.11. What is the correct frequency list for English letters?
8.12. What is the Enigma?
8.13. How do I shuffle cards?
8.14. Can I foil S/W pirates by encrypting my CD-ROM?
8.15. Can you do automatic cryptanalysis of simple ciphers?
8.16. What is the coding system used by VCR+?
9. Other Miscellany
9.1. What is the National Security Agency (NSA)?
9.2. What are the US export regulations?
9.3. What is TEMPEST?
9.4. What are the Beale Ciphers, and are they a hoax?
9.5. What is the American Cryptogram Association, and how do I get in touch?
9.6. Is RSA patented?
9.7. What about the Voynich manuscript?
10. References
10.1. Books on history and classical methods
10.2. Books on modern methods
10.3. Survey articles
10.4. Reference articles
10.5. Journals, conference proceedings
10.6. Other
10.7. How may one obtain copies of FIPS and ANSI standards cited herein?
10.8. Electronic sources
10.9. RFCs (available from [FTPRF])
10.10. Related newsgroups
------------------------------
From: [EMAIL PROTECTED]
Crossposted-To: talk.politics.crypto,sci.answers,news.answers,talk.answers
Subject: Cryptography FAQ (02/10: Net Etiquette)
Date: 29 Aug 1999 10:40:47 GMT
Reply-To: [EMAIL PROTECTED]
Archive-name: cryptography-faq/part02
Last-modified: 94/06/13
This is the second of ten parts of the sci.crypt FAQ. The parts are
mostly independent, but you should read the first part before the rest.
We don't have the time to send out missing parts by mail, so don't ask.
Notes such as ``[KAH67]'' refer to the reference list in the last part.
The sections of this FAQ are available via anonymous FTP to rtfm.mit.edu
as /pub/usenet/news.answers/cryptography-faq/part[xx]. The Cryptography
FAQ is posted to the newsgroups sci.crypt, talk.politics.crypto,
sci.answers, and news.answers every 21 days.
Contents:
2.1. What groups are around? What's a FAQ? Who am I? Why am I here?
2.2. Do political discussions belong in sci.crypt?
2.3. How do I present a new encryption scheme in sci.crypt?
2.1. What groups are around? What's a FAQ? Who am I? Why am I here?
Read news.announce.newusers and news.answers for a few weeks. Always
make sure to read a newsgroup for some time before you post to it.
You'll be amazed how often the same question can be asked in the same
newsgroup. After a month you'll have a much better sense of what the
readers want to see.
2.2. Do political discussions belong in sci.crypt?
No. In fact some newsgroups (notably misc.legal.computing) were
created exactly so that political questions like ``Should RSA be
patented?'' don't get in the way of technical discussions. Many
sci.crypt readers also read misc.legal.computing, comp.org.eff.talk,
comp.patents, sci.math, comp.compression, talk.politics.crypto,
et al.; for the benefit of people who don't care about those other
topics, try to put your postings in the right group.
Questions about microfilm and smuggling and other non-cryptographic
``spy stuff'' don't belong in sci.crypt either.
2.3. How do I present a new encryption scheme in sci.crypt?
``I just came up with this neat method of encryption. Here's some
ciphertext: FHDSIJOYW^&%$*#@OGBUJHKFSYUIRE. Is it strong?'' Without a
doubt questions like this are the most annoying traffic on sci.crypt.
If you have come up with an encryption scheme, providing some
ciphertext from it is not adequate. Nobody has ever been impressed by
random gibberish. Any new algorithm should be secure even if the
opponent knows the full algorithm (including how any message key is
distributed) and only the private key is kept secret. There are some
systematic and unsystematic ways to take reasonably long ciphertexts
and decrypt them even without prior knowledge of the algorithm, but
this is a time-consuming and possibly fruitless exercise which most
sci.crypt readers won't bother with.
So what do you do if you have a new encryption scheme? First of all,
find out if it's really new. Look through this FAQ for references and
related methods. Familiarize yourself with the literature and the
introductory textbooks.
When you can appreciate how your cryptosystem fits into the world at
large, try to break it yourself! You shouldn't waste the time of tens
of thousands of readers asking a question which you could have easily
answered on your own.
If you really think your system is secure, and you want to get some
reassurance from experts, you might try posting full details of your
system, including working code and a solid theoretical explanation, to
sci.crypt. (Keep in mind that the export of cryptography is regulated
in some areas.)
If you're lucky an expert might take some interest in what you posted.
You can encourage this by offering cash rewards---for instance, noted
cryptographer Ralph Merkle is offering $1000 to anyone who can break
Snefru-4---but there are no guarantees. If you don't have enough
experience, then most likely any experts who look at your system will
be able to find a flaw. If this happens, it's your responsibility to
consider the flaw and learn from it, rather than just add one more
layer of complication and come back for another round.
A different way to get your cryptosystem reviewed is to have the NSA
look at it. A full discussion of this procedure is outside the scope
of this FAQ.
Among professionals, a common rule of thumb is that if you want to
design a cryptosystem, you have to have experience as a cryptanalyst.
------------------------------
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