NODE fff7c261[reformatted] how secure can privasoft be?
anonymous@freezone.remailerFri, 20 Oct 95 13:40:36 PDT
heres a version with eighty character lines:
============================================================================
How Secure Can PrivaSoft Be?
Introduction
PrivaSoft is a communication security product, and the user is entitled to
know how secure it is. This document addresses the question of cryptographic
strength of PrivaSoft.
Export license regulations
In some advanced countries, cryptographic products are categorized as
"munitions" and their use, sale or exportation is controlled by local
licensing regulations. PrivaSoft has obtained an export license from the
governments of Israel and the USA. Licenses in other countries are obtained
in coordination with the local distributors.
The typical policy is to limit the allowable cryptographic strength of
commercial products to a level that is strong enough for commercial purposes.
The basic intention of this regulation is to protect the state from abuse of
too strong cryptographic products by terrorists and criminals. Some countries
do not practice such law because it is viewed as a denial of freedom of
expression. PrivaSoft willfully complies with these regulations as it is a
commercial product, and it is not intended for national security applications
with its current key length which is the maximum legally allowable for
commercial users.
The cryptographic engine of PrivaSoft
PrivaSoft uses a pseudo-random generator that is seeded by a 9 digit number
uniformly normalized from the user's secret key. The engine is proprietary,
designed according to the rules of modern cryptology to make the best use of
the allowable key length.
Like other dependable cryptographic engines, the structure of the encryption
software can be disclosed without compromising the security of the user.
However, the coding and specific parameters of the mechanism are considered a
trade secret and will be disclosed for the purpose of cryptoanalytic
validation when necessary and under an appropriate non-disclosure non-
competition agreement.
The use of default keys
When secret keys or passwords are used by laymen, there is always a conflict
between security and convenience: The user tends to use fixed, easily
memorized keys again and again, while the cryptoanalyst only waits for an
opportunity to see many messages encrypted by the same key. PrivaSoft, being
a secure commercial product must live in peace with both - allow the user to
use a repetitive, default key, and deny the cryptoanalyst the pleasure of
having many messages encrypted by one key. This is done by using the pseudo-
random "key extension" feature which is described in the PrivaSoft user's
guide.
The information contents a clear message
If a cryptographic product is properly designed, then the almost only way to
crack it is to try all possible keys. If the process is done by a computer,
the "cracking"" software must be taught to tell the correct key from the
wrong keys. This can only be done if there are some properties of the
decrypted message that are known a - priori. With the PrivaSoft analogue
graphical encryption, and with the naturally noisy fax images, a significant
portion of the page must be reconstructed, and a significant amount of
mathematical correlation must be calculated between neighboring areas of the
image, before the cracking software can tell whether the candidate key is
wrong. This makes the cracking process much slower than in alphanumeric
encryption of the text in a natural language. The 9 digit key, when applied
to analogue, the graphical encryption is equivalent to a much longer key
applied to alphanumeric encryption. The cryptographically oriented user can
make it very much harder by some smart pre-processing of the image prior to
its encryption. A simple example: For a short message, increasing the font
size of the text by a factor of 10 will significantly increase the time
required for breaking the encryption.
Customized versions of PrivaSoft
PrivaSoft is unique in being a one-stop product than can serve all types of
modern correspondence, including E-mail, fax and paper printouts. Special
applications that need and can obtain a license to use non-commercial
cryptographic engines can be accommodated by special versions of PrivaSoft.
The cryptographic engine can be customer-furnished and customer integrated,
however - since in some areas the integration of this product with certain
cryptographic engines may be considered "munitions", each customized version
of the product has to be licensed separately in accordance with the laws of
the territory where it was created and used.
==========================================================================
NODE 9df836deRe: [reformatted] how secure can privasoft be?
futplex@pseudonym.com (Futplex)Fri, 20 Oct 95 21:01:16 PDT
> PrivaSoft has obtained an export license from the governments of Israel and
> the USA.
[...]
> PrivaSoft willfully complies with these regulations as it is a commercial
> product, and it is not intended for national security applications with its
> current key length which is the maximum legally allowable for commercial
> users.
>
> The cryptographic engine of PrivaSoft
>
> PrivaSoft uses a pseudo-random generator that is seeded by a 9 digit number
> uniformly normalized from the user's secret key. The engine is proprietary,
> designed according to the rules of modern cryptology to make the best use of
> the allowable key length.
This seems paradoxical. PrivaSoft uses a key approximately 30 bits long. It
is claimed that the key length "is the maximum legally allowable for
commercial users". How does this square with (to pick a familiar example) the
40 bit RC4 keys used in the exportable international version of Netscape
Navigator ?
Two possible explanations I can imagine are:
(0) PrivaSoft actually uses a key longer than 9 digits, and someone just made
a mistake somewhere along the line. Perhaps it's really 9 extended-ASCII
characters == 9 bytes == 72 bits, rather than 9 digits ==
ceil(9*lg(10)) bits == 30 bits.
(1) NSA believes it is about (2^40)/(2^30) == 1024 times harder to break
the PrivaSoft scheme than SSL with 40-bit RC4. That would be remarkable.
[...]
> The use of default keys
>
> When secret keys or passwords are used by laymen, there is always a conflict
> between security and convenience: The user tends to use fixed, easily
> memorized keys again and again, while the cryptoanalyst only waits for an
> opportunity to see many messages encrypted by the same key.
I get the feeling you are confusing two separate issues here. Users do tend
to use easily memorized passphrases, which is indeed a problem, because such
passphrases are in general easy to guess. But cryptosystems are generally
meant to resist attacks based on the cryptanalyst gaining access to many
ciphertexts, even if all were encrypted with a single key.
[...]
> A simple example: For a short message, increasing the font
> size of the text by a factor of 10 will significantly increase the time
> required for breaking the encryption.
Anyone know how to get 120 point text in LaTeX ?
> Customized versions of PrivaSoft
>
> PrivaSoft is unique in being a one-stop product than can serve all types of
> modern correspondence, including E-mail, fax and paper printouts. Special
> applications that need and can obtain a license to use non-commercial
> cryptographic engines can be accommodated by special versions of PrivaSoft.
> The cryptographic engine can be customer-furnished and customer integrated,
> however - since in some areas the integration of this product with certain
> cryptographic engines may be considered "munitions", each customized version
> of the product has to be licensed separately in accordance with the laws of
> the territory where it was created and used.
I think this is a smart idea.
-Futplex <futplex@pseudonym.com>
NODE 70f882ffRe: [reformatted] how secure can privasoft be?
Jiri Baum <jirib@sweeney.cs.monash.edu.au>Mon, 23 Oct 95 18:39:28 PDT
-----BEGIN PGP SIGNED MESSAGE-----
Hello privsoft@ix.netcom.com
and cypherpunks@toad.com (Cypherpunks Mailing List)
and futplex@pseudonym.com (Futplex)
F. writes:
...
> > The cryptographic engine of PrivaSoft
> >
> > PrivaSoft uses a pseudo-random generator that is seeded by a 9 digit number
> > uniformly normalized from the user's secret key. The engine is proprietary,
> > designed according to the rules of modern cryptology to make the best use of
> > the allowable key length.
>
> This seems paradoxical. PrivaSoft uses a key approximately 30 bits long. It
...
> Two possible explanations I can imagine are:
>
> (0) PrivaSoft actually uses a key longer than 9 digits, and someone just made
...
Could it be 9 hex digits = 36 bits?
Perhaps there's an even bigger paradox in there:
"
The engine is proprietary, designed according to the rules of modern
cryptology.
"
Now I'm not familiar with the rules cited, but wouldn't proprietary
tend to go against them?
> [...]
> > The use of default keys
...
> meant to resist attacks based on the cryptanalyst gaining access to many
> ciphertexts, even if all were encrypted with a single key.
Perhaps theirs isn't? Could be a Freudian slip, you know...
> [...]
> > A simple example: For a short message, increasing the font
> > size of the text by a factor of 10 will significantly increase the time
> > required for breaking the encryption.
>
> Anyone know how to get 120 point text in LaTeX ?
Don't worry, the whole thing sounds bogus anyway. I'd say a larger
font would make it *easier* to break (more correlation per pixel).
They probably think it'll be harder because there's more pixels.
In the original message (NOTE CHANGE IN INDENT!):
> From: anonymous@freezone.remailer
...
> Introduction
>
> PrivaSoft is a communication security product, and the user is entitled to
> know how secure it is. This document addresses the question of cryptographic
> strength of PrivaSoft.
No it doesn't.
> Export license regulations
>
> In some advanced countries, cryptographic products are categorized as
> "munitions" and their use, sale or exportation is controlled by local
> licensing regulations. PrivaSoft has obtained an export license from the
> governments of Israel and the USA. Licenses in other countries are obtained
...
All right, I guess it does. USA approved export, so it must be very weak.
...
> The basic intention of this regulation is to protect the state from abuse of
> too strong cryptographic products by terrorists and criminals.
...
Is it? I think there are one or two people on this list who think the
intention is otherwise...
...
> The use of default keys
...
> This is done by using the pseudo-
> random "key extension" feature which is described in the PrivaSoft user's
> guide.
Do they mean "salt"? If so why don't they say it?
If not, what *do* they mean?
> The information contents a clear message
This is a strange title (I suspect "of" dropped out), but it might
well sum it all up :-)
> If a cryptographic product is properly designed, then the almost only way to
A big "if", if I might say so.
...
> a significant
> portion of the page must be reconstructed, and a significant amount of
> mathematical correlation must be calculated between neighboring areas of the
> image, before the cracking software can tell whether the candidate key is
...
This can at most buy you a constant factor - useful, but not very.
I doubt the two uses of "significant", too. Anybody remember those
diagrams in Typing textbooks about the layout of a letter?
...
> Customized versions of PrivaSoft
>
...
> The cryptographic engine can be customer-furnished and customer integrated,
...
What do they mean by this bit?
Sorry about being so negative, but it is necessary when evaluating security.
Jiri
- --
If you want an answer, please mail to <jirib@cs.monash.edu.au>.
On sweeney, I may delete without reading!
PGP 463A14D5 (but it's at home so it'll take a day or two)
PGP EF0607F9 (but it's at uni so don't rely on it too much)
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