Strength in Complexity?

[Arshad Noor]

Steven M. Bellovin wrote:

> I did see one possible red flag in
> the article: "the key server verifies the client request, then
> encrypts, digitally signs, and escrows the key in a database".
> Escrowed keys are potentially *very* dangerous, but without knowing
> just what's being stored and how it's being protected, I can't say 
> more.

I appreciate the affirmation from Perry and Steven (so far) that
I'm not off-base wrt designing security with simplicity in mind.
I will confirm that security has taken precedence over simplicity
where it was necessary to make a trade-off and where security was
the primary goal.

To respond to your concern, Steven, the escrowed symmetric keys
are encrypted using a Public Key from an asymmetric key-pair (the
recommended key-size is 2048-4096 bits RSA).

The Private Key of the RSA key-pair capable of decrypting the
escrowed keys is recommended to be generated and stored on a FIPS
140-2 Level 3 (or greater) certified HSM.

For activating the HSM to use the Private Key by the SKMS service,
it is recommended to use M of N FIPS-certified smartcards for strong
authentication, so that no single individual is capable of accessing
the Private Key (and consequently, any of the escrowed symmetric
keys) on their own.

(For those interested, an ACM paper on an earlier DRAFT version of
the protocol/architecture of the SKSML protocol is available at:
http://middleware.internet2.edu/idtrust/2008/papers/07-noor-ekmi.pdf
I hope to inform this forum of the public availability of a more
recent DRAFT of the protocol within the next two weeks, for review
and comments.  We, on the OASIS committee will be grateful for any
feedback we get from this forum).

My understanding of cryptography, after spending 9 years deploying
PKIs - large and small - is that it is necessary to use a combination
of strong technology and procedures for effective security.  Relying
on just one component alone can lead to a breakdown in security (as
my experience has shown me).

Arshad Noor
StrongAuth, Inc.

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