Re: software crypto is useless

From: Henrick Hellström (henrick.hellstrm_at_telia.com)
Date: 05/08/03 

Date: Thu, 08 May 2003 06:23:16 GMT

????? wrote:
> No matter what crypto algorithm you use (AES, RSA with LONG keys),
> as long as it is involved with software,
> the cracker has good chances to break your security.
>
> Since runtime debuggers like SoftIce can watch and change your software
> in runtime, your keys, passwords, and signatures, etc. all become doubtful.

...and hardware can simply be replaced for another box that looks just
the same. Each security module, software as well as hardware, has
vulnerabilities, and the only question is whether or not you know of
these vulnerabilities and how to cope with them. Software crypto can be
just fine in case you are not concerned about adversaries who get access
to your box while the software is running (because the probability of
such adversaries is too small compared to the price you would have to
pay for a hardware solution).

> Even if you embed crypto hardware and IC cards into your system, weakness
> still exists. Why? I can put a hash value that I want you to sign, inside your
> system, and later, when you call IC card or crypto HW to sign your own
> document, the software part is changed by me to submit my hash value instead
> of yours, all other parts of the security system work greatly. But you just
> signed a miserable document with the strongest algorithm, key and enven
> hardware.
>
> So, who can help with the above case? Let IC cards sign and transmit your
> documents to your receivers? That will skip all software parts. Or just claim
> that client environment is out of the scope of security?

Each part of the system is within the scope of security. Using hardware
to sign all outgoing communication will not solve the problem you
described in the previous paragraph - it would in fact make it even
easier for an adversary to make you sign documents you didn't intend to
sign. (Think about it.)

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