Cryptography-Digest Digest #387, Volume #11 Wed, 22 Mar 00 08:13:01 EST
Contents:
Gray Code like ([EMAIL PROTECTED])
Re: Gray Code like (Mok-Kong Shen)
Re: Factoring Large Numbers - I think I figured it out! (Johnny Bravo)
Re: Non-doublespending offline digital money? (Johnny Bravo)
Re: multiple encryption (Johnny Bravo)
Encryption and decryption in C ([EMAIL PROTECTED])
Re: multiple encryption ([EMAIL PROTECTED])
Re: pgp key collision ("Christoph Moser")
Re: Gray Code like (Francois Grieu)
Re: pgp key collision (Tom McCune)
Re: Concerning UK publishes "impossible" decryption law ("�R���")
Re: pgp key collision (Lutz Donnerhacke)
Re: Encryption and decryption in C (Runu Knips)
Re: Concerning UK publishes "impossible" decryption law ("�R���")
Re: Gray Code like ([EMAIL PROTECTED])
Re: pgp key collision ([EMAIL PROTECTED])
----------------------------------------------------------------------------
From: [EMAIL PROTECTED]
Subject: Gray Code like
Date: Wed, 22 Mar 2000 08:58:21 GMT
My excuses in advance if this is not a valid question in this group.
I have encountered a form of encoding that's very similar to Gray Code,
but isn't quite the same. In Gray Code only a single symbol at a single
position may change when you move to an adjecent code word. What I'm
looking at here is a list of code words where a new symbol is shifted in
from the right when you move to the next code word and all codewords are
unique.
An example:
000
001
010
101
011
111
110
100
which isn't a Gray Code since moving from the second to the thrid code
word you'll change two positions and not just one.
My question is if anyone knows what this kind of encoding is called and
if there is any litterature about it and its uses.
Thanks in advance,
/Tomas
Sent via Deja.com http://www.deja.com/
Before you buy.
------------------------------
From: Mok-Kong Shen <[EMAIL PROTECTED]>
Subject: Re: Gray Code like
Date: Wed, 22 Mar 2000 10:32:19 +0100
[EMAIL PROTECTED] wrote:
>
> An example:
>
> 000
> 001
> 010
> 101
> 011
> 111
> 110
> 100
>
> which isn't a Gray Code since moving from the second to the thrid code
> word you'll change two positions and not just one.
>
> My question is if anyone knows what this kind of encoding is called and
> if there is any litterature about it and its uses.
There is no apparent advantage of that over the Gray code. So
why should one give it a special name? (I am not even sure that I
see any systematics in the way the code symbols are generated.)
M. K. Shen
------------------------------
From: Johnny Bravo <[EMAIL PROTECTED]>
Subject: Re: Factoring Large Numbers - I think I figured it out!
Date: Wed, 22 Mar 2000 04:03:23 -0500
On 22 Mar 2000 06:25:20 GMT, [EMAIL PROTECTED] (Paul Rubin) wrote:
>Well, I gotta say, if Richard has a scheme for implementing Shor's
>algorithm on a microchip, that's something that a computer wouldn't be
>able to execute, and would be a fantastic advance useful for all kinds
>of things other than factoring, and even a 10 digit demonstration
>would be extremely impressive (a group at MIT is working on 2 digits).
>
>But somehow I'm not holding my breath.
He says he doesn't know anything about microchips, so he can't have any
idea if it will also work on a computer or not. And he says he has a
method, not a working quantum technology.
A regular computer can implement Shor's algorithm, though it gets
exponentially slow, Low three digit numbers can be factored with it, even
on a old P200.
--
Best Wishes,
Johnny Bravo
"The most merciful thing in the world, I think, is the inability
of the human mind to correlate all it's contents." - HPL
------------------------------
From: Johnny Bravo <[EMAIL PROTECTED]>
Subject: Re: Non-doublespending offline digital money?
Date: Wed, 22 Mar 2000 00:39:11 -0500
On Tue, 21 Mar 2000 16:27:32 -0600, Eric Norman <[EMAIL PROTECTED]>
wrote:
>matt wrote:
>>
>> Could anyone tell me if it is theoretically/physically possible to
>> have a digital cash system which is offline, and prevents double
>> spending?
>
>If every offline transaction eventually leads to a subtraction
>from their account, what double spending is there to worry about?
Let's say I have 50,000 in my account at your bank. Then I spend
$1,000,000 over a week, resell what I bought for $.20 on the dollar.
Orders come in and go way over my account, you have no choice but to cover
the orders.
Then I burn my fake ID, leave the state $150,000 in cash ahead.
And you are now out $950,000.
This is why offline systems are a bad idea.
--
Best Wishes,
Johnny Bravo
"The most merciful thing in the world, I think, is the inability
of the human mind to correlate all it's contents." - HPL
------------------------------
From: Johnny Bravo <[EMAIL PROTECTED]>
Subject: Re: multiple encryption
Date: Wed, 22 Mar 2000 01:00:43 -0500
On Tue, 21 Mar 2000 12:47:06 -0700, Jerry Coffin <[EMAIL PROTECTED]>
wrote:
>In article <8b8f8q$lmk$[EMAIL PROTECTED]>, [EMAIL PROTECTED] says...
>> Hello.
>> If I encrypt my data using short keys (40, 56) more then one time,
>> ( 1 file is encrypting 40 times with 56 bit key ) how it can increase
>> the privacy level ?
>> What if I change the key every time I do my encryption (i.e. 40
>> cycles with 40 different keys). And what will be the equivalent length
>> of the one round encrypting key in this case ?
>
>If it does not form a group, then you can gain at least a little
>strength by using multiple encryption. The exact amount depends on
>the encryption you're using and the attacks you consider reasonable.
>One fairly well-known attack on multiple encryption is known as a
>meet in the middle attack -- it, however, can use a _huge_ amount of
>memory, so it may not be practical for the particular cipher you're
>talking about using.
Without the meet in the middle attack, you can add ln(x) bits to the
encryption, where X is the number of different encryptions used, when
compared to a brute force attack. 40 different keys adds roughly 5 bits,
8 bits for 64 keys. It only ramps down from there, you are better off
using a stronger cipher if possible.
A 56 bit cipher would be equivalent to a message encrypted 65536 times
with a 40 bit cipher using 65536 different keys in a brute force attack.
And the 65536 keys of 40 bits would require 320k of key to be transmitted
in advance. If you have this much available transmitted ahead of time,
and the messages are short enough, a one time pad would be far more
secure.
--
Best Wishes,
Johnny Bravo
"The most merciful thing in the world, I think, is the inability
of the human mind to correlate all it's contents." - HPL
------------------------------
From: [EMAIL PROTECTED]
Subject: Encryption and decryption in C
Date: Wed, 22 Mar 2000 10:50:23 GMT
1.How to encrypt the data below to a file?
1234 3.000000 3.000000 3.000000 3.000000
0234 4.000000 4.000000 2.000000 2.000000
1235 3.000000 3.000000 3.000000 3.000000
0239 4.000000 4.000000 1.000000 2.000000
1584 1.000000 3.000000 3.000000 3.000000
9234 4.000000 4.000000 2.000000 2.000000
5535 3.000000 3.000000 1.000000 3.000000
8239 4.000000 4.000000 2.000000 2.000000
2. How to decrypt the file obtained from Step 1?
Thanks
Sent via Deja.com http://www.deja.com/
Before you buy.
------------------------------
From: [EMAIL PROTECTED]
Subject: Re: multiple encryption
Date: 22 Mar 2000 11:17:59 GMT
In a previous article, Johnny Bravo <[EMAIL PROTECTED]> writes:
[--cut--]
>And the 65536 keys of 40 bits would require 320k of key to be transmitted
>in advance. If you have this much available transmitted ahead of time,
>and the messages are short enough, a one time pad would be far more
>secure.
An OTP would not necessarily be more secure. An OTP would probably be less
secure (i.e. not secure at all) against a known plain text substitution
attack:
The attacker knows that the plain text block number n is mn and wants it to be
m'n instead. Thus he substitutes the cipher block cn for (cn xor mn xor m'n).
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------------------------------
From: "Christoph Moser" <[EMAIL PROTECTED]>
Subject: Re: pgp key collision
Date: Wed, 22 Mar 2000 12:29:46 +0100
Gregory G Rose wrote>...
>In article <8b9j18$j4l$[EMAIL PROTECTED]>,
>Older PGP used 32 bits for the external interface
>to the key ID, and after approximately sqrt(2^32)
>keys are created you have a high probability that
>two of them will have the same key-ID. That is
>about 65,000 keys.
... if you use the Fingerprint, not the KeyID, to identify
a key you have 128 Bit (160 Bit for V4)... and that's
pretty much, although collisions are never impossible.
Christoph
------------------------------
From: Francois Grieu <[EMAIL PROTECTED]>
Subject: Re: Gray Code like
Date: Wed, 22 Mar 2000 12:56:49 +0100
[EMAIL PROTECTED] wrote:
> list of code words where a new symbol is shifted in
> from the right when you move to the next code word and
> all codewords are unique. An example:
> 000
> 001
> 010
> 101
> 011
> 111
> 110
> 100
Never seen this beast before, but something vaguely similar is used in
Twinkle (Shamir's hypothetical factoring device) to make fast counters,
except the right bit is computed as the XOR of two others bits. The
counter, based on an irreducible polynomial, cycles after (2^n)-1 states
where n is the number of bits (instead of 2^n in your case) and is
called a maximal length shift register.
Hope this helps,
Francois Grieu
------------------------------
From: Tom McCune <[EMAIL PROTECTED]>
Subject: Re: pgp key collision
Date: Wed, 22 Mar 2000 12:04:13 GMT
=====BEGIN PGP SIGNED MESSAGE=====
Hash: SHA1
In article <[EMAIL PROTECTED]>,
[EMAIL PROTECTED] wrote:
>i just seached on key server for 0xDEADBEEF and it found 3 keys..
Did you notice that two of these (one RSA, one DSS) belong to the same
person? With Imad's software, you can generate this "short" key ID in a day
or so, but the full key ID won't happen.
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ZOx5eEU1ZKLLSMb+uQ+H2ZrJ
=Q7tH
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------------------------------
From: "�R���" <[EMAIL PROTECTED]>
Crossposted-To:
alt.security.pgp,comp.security.pgp.discuss,alt.security.scramdisk,alt.privacy
Subject: Re: Concerning UK publishes "impossible" decryption law
Date: Wed, 22 Mar 2000 09:35:12 +1100
i would definately like to see this url
"Bobo" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]...
> On Wed, 22 Mar 2000 01:16:18 +1100, "�R���" <[EMAIL PROTECTED]>
said:
>
> >quantitive data, im afraid i am not very up on electronics as much as i
> >would like to be, of course your request works both ways, can you
disprove
> >the posibilty of a magnetic feild powered by the pc to destroy/damage the
> >disk, switched on by a false login, powered through the paralel port? im
not
> >being a smart ass, and i might have shot my mouth off, but i am an idea's
> >man, and like to be proven conclusively wrong. not just flamed
>
> There's a website I saw somewhere that does list just that...mainly it
lists
> the strengh of an elecromagnetic field required to destroy various
magnetic
> media...
>
> Of course, 5.25 floppies would be easiest, then 3.5" disks, videotapes,
DAT's,
> etc. etc.
>
> But hard drives, it does specifically mention, would require such an
intense
> field that it would actually distort the platters and mentioned (I think)
that
> no such degaussers exist except some experimental army type of thing that
you
> probably don't want to build into your computer since it would tend to add
> quite a bit to the cost (yes...being facetious...)
>
> Now...If I could only recall where that web site was...
------------------------------
From: [EMAIL PROTECTED] (Lutz Donnerhacke)
Subject: Re: pgp key collision
Date: 22 Mar 2000 11:52:42 GMT
* Christoph Moser wrote:
>... if you use the Fingerprint, not the KeyID, to identify
>a key you have 128 Bit (160 Bit for V4)... and that's
>pretty much, although collisions are never impossible.
Won't help against DEADBEEF attacks:
$ pgp -kv 0x19980101
Type Bits/KeyID Date User ID
pub> 2048/19980101 1998/01/12 [EMAIL PROTECTED] SIGN EXPIRE:1999-12-31
Ueberregionale CA des Individual Network e.V.
Expire: 1999/12/31
pub> 2048/19980101 1998/01/12 [EMAIL PROTECTED] SIGN EXPIRE:1999-12-31
Root CA des Individual Network e.V.
Expire: 1999/12/31
2 matching keys found.
$ pgp -kvc 0x19990101 ~/work/crypt/data/pubring.pgp
Type Bits/KeyID Date User ID
pub 2048/19990101 1999/01/15 Root CA des Individual Network e.V.
<[EMAIL PROTECTED]> (SIGN EXPIRE:2000-12-31)
Expire: 2000/12/31 SIGNature only
Key fingerprint = 19 99 01 15 02 B4 7A 6B 33 D9 58 EE FC 09 8C E6
Key generation tooks s few minutes for the first ones. The last example
required four hours computing to modify the fingerprint to the current date
and time. SHA-1 Fingerprints are as easy to fool. So v4 KeyIDs are not
unique as described (at last in the draft to) RfC 2440.
------------------------------
Date: Wed, 22 Mar 2000 13:25:58 +0100
From: Runu Knips <[EMAIL PROTECTED]>
Subject: Re: Encryption and decryption in C
[EMAIL PROTECTED] schrieb:
> 1.How to encrypt the data below to a file?
> 2.How to decrypt the file obtained from Step 1?
"My computer doesn't work. Please explain how I can
make it work again."
One can't answer such questions if one doesn't have
enough informations. You have some data, fine. You
want to program in C, fine. You want to encrypt that
data, fine.
But what do you want to do ??? 3DES ? Mars ? RC4 ?
RC6 ? Blowfish ? Twofish ? IDEA ? RSA ? ElGamal ?
What encryption do you want to use, and which libary
do you want to use ?????
Get a libary such as OpenSSL (www.openssl.org) and
ask again if you need any help with it !
------------------------------
From: "�R���" <[EMAIL PROTECTED]>
Crossposted-To:
alt.security.pgp,comp.security.pgp.discuss,alt.security.scramdisk,alt.privacy
Subject: Re: Concerning UK publishes "impossible" decryption law
Date: Wed, 22 Mar 2000 23:45:04 +1100
i do a bit of gardening, and i use anon mostly to ask for advise in
particular groups, so i dont think i would come to the attention enough to
warrant EM microscopy techniques.
"Nemo Outis" <[EMAIL PROTECTED]> wrote in message
news:61UB4.6482$[EMAIL PROTECTED]...
> It is *easy* to encounter/use a magnet strong enough to disrupt the
*normal*
> read process of a hard drive - however, it is *extremely difficult*
(i.e.,
> virtually impossible for ordinary folks) to build/buy/acquire a magnet
> sufficiently strong to remove all residual magnetic traces of data to the
> point that very sophisticated EM microscopy techniques cannot recover the
> data.
>
> The good news is that such EM microscopy techniques are (almost) never
used in
> ordinary or even not-so-ordinary police investigations - they are the
preserve
> of NSA type agencies.
>
> Regards,
>
>
> In article <8b8rvq$eop$[EMAIL PROTECTED]>,
> [EMAIL PROTECTED] (Otto Sykora) wrote:
> >>> an electric magnet is not so hard to make or get hold of, its
> >harmless
> >> unless power is given to it, and when powered, can be easily be strong
> >> enough to destroy data an the disks.
> >
> >I find that difficult to believe Can you provide figures to
> >justify your assertion?
> ><<
> >
> >why should it be difficult to destroy data on disk with a magnet?
> >Small example , this time with small permanent magnet:
> >in some trains in Germany, they have seats similar like in airplane,
> >the small table integrated in the seat in front of you is held in the
> >stoved position by two small permament magnets. When people used this
> >table as support for some types of laptop computer, their harddrivs
> >were sudenly partialy erased. Just because of the small magnet placed
> >abt half inch from the drive.
> >
------------------------------
From: [EMAIL PROTECTED]
Subject: Re: Gray Code like
Date: Wed, 22 Mar 2000 12:39:04 GMT
> There is no apparent advantage of that over the Gray code. So
> why should one give it a special name? (I am not even sure that I
> see any systematics in the way the code symbols are generated.)
>
> M. K. Shen
This is not meant as a substitute for Gray Codes, since their
properties are very different. It is used in cyclic stacks where the
contents of a moving window of the size of the code word the stack is
based on will always point out a unique location in the stack. If you
choose any column in the sequence of code words I provided as an example
and write them in a circle, you'll see that taking any three adjecent
symbols will uniquely specify its position. Since this is already used
in some litterature under the faulty name "Gray Coding" and I plan on
using it in future essays I don't want to continue spreading the faulty
name or risk introducing yet another faulty name for it.
Bracelet encoding could be a descriptive name since the sequence of
codewords bites its own tail. Anyone recognize a name for this type of
encoding?
Thanks in advance,
/Tomas
Sent via Deja.com http://www.deja.com/
Before you buy.
------------------------------
From: [EMAIL PROTECTED]
Subject: Re: pgp key collision
Date: Wed, 22 Mar 2000 12:51:10 GMT
=====BEGIN PGP SIGNED MESSAGE=====
Hash: SHA1
Lutz Donnerhacke wrote:
> * Christoph Moser wrote:
> >... if you use the Fingerprint, not the KeyID, to identify
> >a key you have 128 Bit (160 Bit for V4)... and that's
> >pretty much, although collisions are never impossible.
>
> Won't help against DEADBEEF attacks:
>
> $ pgp -kv 0x19980101
> Type Bits/KeyID Date User ID
> pub> 2048/19980101 1998/01/12 [EMAIL PROTECTED] SIGN EXPIRE:1999-12-31
> Ueberregionale CA des Individual Network e.V.
> Expire: 1999/12/31
> pub> 2048/19980101 1998/01/12 [EMAIL PROTECTED] SIGN EXPIRE:1999-12-31
> Root CA des Individual Network e.V.
> Expire: 1999/12/31
> 2 matching keys found.
it helps,
my pgp 6.5.3 shows that the fingerprints are different for these keys:
C40E 2C31 1DDB 5FDB AF5F 2CAF 9D44 1310 for Ueberregionale CA des Individual Network
e.V.
B306 9A8D 3804 3C75 4132 EEDC 8B7D 610D for Root CA des Individual Network e.V.
> $ pgp -kvc 0x19990101 ~/work/crypt/data/pubring.pgp
> Type Bits/KeyID Date User ID
> pub 2048/19990101 1999/01/15 Root CA des Individual Network e.V.
> <[EMAIL PROTECTED]> (SIGN EXPIRE:2000-12-31)
> Expire: 2000/12/31 SIGNature only
> Key fingerprint = 19 99 01 15 02 B4 7A 6B 33 D9 58 EE FC 09 8C E6
>
> Key generation tooks s few minutes for the first ones. The last example
> required four hours computing to modify the fingerprint to the current date
> and time. SHA-1 Fingerprints are as easy to fool. So v4 KeyIDs are not
> unique as described (at last in the draft to) RfC 2440.
- --
Disastry
http://i.am/disastry/
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------------------------------
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