Re: Draft Edition of LibTomMath book

2003-06-28 Thread Peter Gutmann
Werner Koch [EMAIL PROTECTED] writes:

Does the proprietary SSH still use GMP?  I know no other major crypto apps
using GMP for big number math.  

I've seen it used in a couple of lesser-known apps that I played with for
interop testing, nothing that counts as a major app though.  Maybe it's being
used by people who prefer the LGPL to the more widely-used OpenSSL bignum
lib's BSD license (or perhaps it's the fact that GMP has documentation :-).

A problem with GMP is that it heavily uses alloca() and thus it is not that
hard to find traces of secrets in the core.

Ouch!  This is a pity, because GMP seems to have the most active development
in terms of both algorithm optimisation and machine-specific optimisations -
if you want to find a version that runs well on $obscure_embedded_platform,
it's pretty much GMP or nothing.

Peter.


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Re: Draft Edition of LibTomMath book

2003-06-27 Thread Marcel de Riedmatten
Le ven 27/06/2003 à 15:24, Werner Koch a écrit :

 Does the proprietary SSH still use GMP?  I know no other major crypto
 apps using GMP for big number math.  A problem with GMP is that it
 heavily uses alloca() and thus it is not that hard to find traces of
 secrets in the core.

I know that freeswan use it. 

Cheers

-- 
Marcel de Riedmatten
pgp key: CFE703CA http://ftp.dotforge.ch/pub/users/mdr/mdr.gpg.asc
Empreinte: 4687 F9CB D8E2 AC1A B806  F812 C048 0875 CFE7 03CA


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Draft Edition of LibTomMath book

2003-06-25 Thread tom st denis
The Draft Edition of the LibTomMath book [book about how to implement
bignum math] is freely available on my site at

http://book.libtomcrypt.org

Keep in mind it is a draft and has not been edited yet.  However, if
you ever wanted to learn how to implement efficient [portable too]
bignum math routines you might want to give it a read.

Enjoy,
Tom

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re: Draft Edition of LibTomMath book

2003-06-25 Thread tom st denis
Just a quick comment.  The PDF is not a web friendly PDF so you if
you are trying to view it inline with your browser you have to wait for
it to download completely first.

I've managed 80KB/sec off the site so it doesn't take too long to grab
it.Alternatively you can grab the .PDF.BZ2 file and decompress it
locally.  I'm only making this comment because I've noted quite a few
incomplete downloads...

Thanks,
Tom
http://book.libtomcrypt.org

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Re: Draft Edition of LibTomMath book

2003-06-25 Thread bear


On Wed, 25 Jun 2003, tom st denis wrote:

The Draft Edition of the LibTomMath book [book about how to implement
bignum math] is freely available on my site at

http://book.libtomcrypt.org

Keep in mind it is a draft and has not been edited yet.  However, if
you ever wanted to learn how to implement efficient [portable too]
bignum math routines you might want to give it a read.

Enjoy,
Tom

One thing that I've noticed for a long time is that there
are *VERY* few math libraries that don't leave whatever
numbers they're working with in memory when deallocating
(deallocating heap via free() or deallocating stack via
returning from a procedure call or deallocating swapspace
by getting paged back in off a disk).

And numbers that an application leaves lying around in
whatever working memory or media it's using, can be
discovered and exploited by other programs - frequently
by unauthorized ones.

Windowing systems have the same kind of leakage, but you
can avoid using windowing systems with a crypto program;
there's no need to put sensitive information like keys
or passwords on the screen ever.  Admittedly, I'd like
to have a secure windowing system, but it seems unlikely.

But I think Math is indispensable to crypto, and there
ought to be a secure mathematics library.

Bear


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Re: Draft Edition of LibTomMath book

2003-06-25 Thread tom st denis

--- bear [EMAIL PROTECTED] wrote:
 One thing that I've noticed for a long time is that there
 are *VERY* few math libraries that don't leave whatever
 numbers they're working with in memory when deallocating
 (deallocating heap via free() or deallocating stack via
 returning from a procedure call or deallocating swapspace
 by getting paged back in off a disk).
 
 And numbers that an application leaves lying around in
 whatever working memory or media it's using, can be
 discovered and exploited by other programs - frequently
 by unauthorized ones.

Very true.  LibTomMath will actually wipe the memory allocated [via
memset] before free'ing but I leave it up to the end user to lock their
heap from swapping.

Tom

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