Monday, December 12, 2005

Re: X.509 / PKI, PGP, and IBE Secure Email Technologies

James A. Donald wrote:
> This was the scenario envisaged when PKI was created,
> but I don't see it happening, and in fact attempting to
> do so using existing user interfaces is painful. They
> don't seem designed to do this.
> My product, Crypto Kong, was
> designed to directly support this scenario in a more
> convenient fashion - it keeps a database of past
> communications and their associated keys, but there did
> not seem to be a lot of interest. I could have made it
> more useful, given it more capabilities, but I felt I
> was missing the point

i've seen some discussions that were either/or regarding pki & pgp;
aka pki advocates attempting to position pki as a OR to pgp. the issue
is that both pki and pgp require a local trusted public key repository
as the basis for establishing trust.

pki then layers on it, these certification authority business processes,
specialized digitally signed messages called digital certificates, etc
to address first time communication between strangers where the relying
parties have no other resources for determining information about the
sender in an offline environment. they then advocate that all
(personally) digitally signed operations are required to have attached
x.509 identity digital certificates that has been digitally signed by a
certification authority.

we saw some of that when we did work on the cal. state & fed. electronic
signature legislation

one possible interpretation might be that it would have increased the
revenue stream for the certification authority industry.

drastically improving the useability of the interface to the trusted
public key repositories could be viewed as having two downsides 1)
certification authorities that haven't payed to have their public keys
preloaded can more easily join the club, 2) the pgp-like scenario
becames much easier, potentially drastically reducing existing reliance
on the digital-certificate-only (and certification authority only
business process) digital-signed-operation model.

part of the problem with the trusted third party certification authority
model is that its primary benefit in the case of first time
communication betweeen two strangers ... where the relying party has no
other recourse to information about the other party. this is actually an
extremely small percentage of communications. we saw some of this
working on the original e-commerce activity

where we layed out hypothetical certification issues for merchants ...
including things like having FBI background checks for all merchant
employees. the problem is that e-commerce transactions have been quite
bi-model whith the largest percentage of transaction occuring as repeat
business with well-known merchants. in these cases, consumers have
established trust via a large number of other mechanisms ... so there is
little added value that a certification authority can provide ...
especially if they aren't willing to stand-behind and guarantee all
merchant transactions (ssl then is primarily countermeasure to
mitm-attack and evesdropping on transaction as opposed to a
certification/trust issue).

the rest of the remaining transaction are spread around to a large
number of different merchants having a few transactions each. the issue
here is that the incremental revenue flow for a few transactions a month
couldn't possibly cover the cost of a certification process that
involved things like fbi background checks on all merchant employees.

the large majority of transactions are either repeat business and/or
with extremely well-known merchants ... this doesn't satisfy the PKI
target profile of first time communication between complete strangers.
simple countermeasure to mitm-attack and countermeasure is achieved by
having stored the merchant's public key (from the consumer's standpoint).

from the merchant standpoint they already have transaction guarantees on
credit card processing from their contract with financial institution.
the threat/vulnerability model here is client-originated fraudulent
transactions that aren't strongly authenticated. here, x9.59 standard

allows for digitally signed transaction where the public key is
registered with the consumer's financial institution and the digital
signature is verified by the consumer's financial institution as part of
verifying the transaction.

the other part of x9.59 standard is that it specifies that account
numbers used in x9.59 transactions can't be used in non-authenticated
transactions. this eliminates both data breaches and evesdropping as a
threat/vulnerability for fraudulent financial transactions ... aka the
requirement given the x9a10 working group for x9.59 standard was to
preserve the integrity of the financial infrastructure for all retail
payments. if data breaches and evedsdropping no longer can result in
fraudulent transactions, then there is much less reason for
sophisticated countermeasures for those threat/vulnerabilities (ssl is
no longer needed to prevent evesdropping on the account number, since
evesdropping on the account number no longer provides any practical
fraudulent benefit).

simple public key registration as part of financial account operation
(in an onging relationship that a consumer has with their financial
institution) not only is a certificateless digital signature model

but also eliminates much of the requirement for existing major use of
digital certificates; that of providing ssl encrypted communication

as countermeasure for evesdropping for the purpose of account number

furthermore, not only does simple x9.59 digital signature authenticated
transactions eliminate the threat/vulnerability of evesdropping for
account number harvesting, but it also eliminates the
threat/vulnerability of data breaches for account number harvesting
aka the harvesting could still go on, but the threat/vulnerability of
fraudulent transactions as a consequence of harvesting is eliminated ...
note that phishing attacks for the purpose of account number harvesting
is also eliminated as a threat/vulnerability ... phishing can still go
on, account numbers cna still be harvested, the account numbers are
useable for fraudulent transactions w/o the digital signature.

misc. past posts mentioned bi-model transaction distribution and/or
having suggested employee fbi background checks as part of merchant
certification process. [FYI] Did Encryption
Empower These Terrorists? SSL certs & baby steps E-commerce security???? Does "Strong Security" Mean

Anne & Lynn Wheeler

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