At 12:02 PM 6/4/2003 +0100, Dave Howe wrote:
For that matter, our system here discards the CC after use (the pre-auth
step with the merchant bank agent gives us back a "fulfillment handle" that
can only be used to fulfill or cancel that individual transaction - but of
course Amazon *want* to keep your CC details so they can do their
fast-checkout patented thingy.

the ground rules given the x9a10 working group for the x9.59 standard was to preserve the integrity of the financial infrastructure for all (credit, debit, stored-value, POS, internet, non-internet, aka ALL) electronic retail payments. it was one of the things that led us down the path of certless operation. We had previously done the work on the original payment gateway and had to perform various kinds of due diligence on all the major CA vendors .... which started to dawn on us that stale, static certificates were actually redundant and superfluous in the financial business process.

sort of the clinker was starting to do operational and performance profile on any of the existing payment networks .... and it was evident that there was a huge mismatch between the existing payment transaction payload size and any of the commonly used certificates (even the drastically simplified replying-party-only certificates carrying only an account number and public key).

Two major characteristics of X9.59 was that it would provide 1) end-to-end authentication (aka the consumers financial institution would be the one responsible for performing authentication) and 2) account numbers used in X9.59 transactions could not be used in unauthenticated transactions.

Some of the '90s digitally signature oriented specifications had authentication occurring at the internet boundary and stripping off the certificate (avoiding the extreme certificate payload penalty in the payment network). The downside was that the party performing the authentication didn't necessarily have the consumer's interest in mind and Visa subsequently presented statistics at a ISO standards meeting on the number of transactions flowing through the network 1) with a flag claiming to have been digitally signature authenticated and 2) they could prove that no digital signature technology was ever involved.

Evesdropping, sniffing or harvesting account numbers in the current infrastructure (at any point in the process, by insiders or outsiders, traditionally financial exploits have been 90 percent insiders) can result in fraudulent transactions. As a result, existing account numbers effectively become a form of shared-secret and need to be protected. With the X9.59 business rule requiring the account number to only be used in authenticated transactions, simple harvesting of a X9.59 account number doesn't result in fraud. Issuing financial institutions then can use existing business processes that support mapping of different account numbers to the same account. A discussion of the security proportional to risk with regard to credit card transactions: Net banking, is it safe?

The issue with the use of SSL for protecting credit card transactions isn't addressing all or even the major vulnerability to the infrastructure. Eliminating the account number as a form of shared secret addresses all of the vulnerabilities, not just the transaction-in-flight vulnerability addressed by SSL. As a byproduct of addressing all of the shared-secret related vulnerabilities, it also eliminates the need to use SSL for protecting the shared secret while being transmitted.

Detailed report of its use in the NACHA debit network trials can be found at
scroll down to "July 23, 2001: Digital Signatures Can Secure ATM Card Payments"

More details of X9.59 standard:

Anne & Lynn Wheeler
Internet trivia 20th anv

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