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At 04:57 PM 10/11/00 -0700, Meyer Wolfsheim wrote:
The only reasons I see for having a security system (be it
an encryption product, or a physical access device) with a
large discrepancy in the level of security that the
individual components provide is either:
...
I'd add one more reason to yours, which is especially
relevant in the crypto world:
d) Use of standard components.
If it costs nothing more to use Rijndael to encrypt all your
data than to use FEAL-8, then why not go ahead and use
Rijndael, which is widely available in crypto libraries and
such? Okay, so your system doesn't even provide FEAL-8
level security, but there's no reason to go out of your way
to use a bad cipher, along with all the other problems,
right? (I've often suspected that if all fielded encryption
in use today were replaced by FEAL-8X (FEAL-8 with 128-bit
keys), there would be virtually no impact on practical
security. I think the best know attack requires 2^{25}
known plaintexts, which are almost never available in
practice.)
This is the situation that we would have if all-but-
unpickable locks cost exactly the same amount as the crappy
toy locks they usually sell with luggage.
I am disgusted by the use of security devices purely for
marketing reasons. The mentality that "It doesn't matter
that we can't provide quality entropy in our encryption
product as long as we can say we use 256 bit Twofish" is
demonstrative of negligence. I want to be told the security
of the *weakest* part of the system, as that is the measure
of the entire system's security. Then I will decide if it is
sufficient for me.
I agree in principle, but in practice, some of these
measures are a lot easier to figure out than others. Like,
it's easy to see determine that you're using a cipher with a
sufficiently long key and a good pedigree. It's harder to
determine whether your PRNG always gets as much entropy as
it needs to generate unguessable keys. It's still harder to
determine whether anyone your CA ever hires will be willing
to generate a few new keys that are supposed to be in your
hierarchy, and use them to run some kind of fraud on your
system. Or that there are no software flaws that make it
easy to defeat the system, despite the use of first-rate
components. Or
...
Security is a ritual, not a product.
:)
- -MW-
--John Kelsey, Counterpane Internet Security, [EMAIL PROTECTED]
PGP Fingerprint: 5D91 6F57 2646 83F9 6D7F 9C87 886D 88AF
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